XRP Ledger Standards

  xls: 68
  title: Sponsored Fees and Reserves
  description: Allow an account to fund fees and reserves on behalf of another account
  author: Mayukha Vadari (@mvadari)
  category: Amendment
  status: Draft
  proposal-from: https://github.com/XRPLF/XRPL-Standards/discussions/196
  requires: XLS-74
  created: 2024-05-02
  updated: 2026-01-30

Sponsored Fees and Reserves¶

1. Abstract¶

This proposal adds a process for users to maintain control over their keys and account, but to have another account (e.g. a platform) submit the transaction and pay the transaction fee and/or reserves on their behalf. This proposal supports both account and object reserves.

Similar features on other chains are often called "sponsored transactions", "meta-transactions", or "relays".

2. Motivation¶

As the blockchain industry grows, many projects want to be able to build on the blockchain, but abstract away the complexities of using the blockchain - users don't need to submit transactions or deal with transaction fees themselves, they can just pay the platform to handle all that complexity (though, of course, the users still control their own keys).

Some projects also want to onboard users more easily, allowing users to create accounts without needing to pay for their own account reserve or needing to gift accounts free XRP to cover the reserve (this could get rather expensive if it is exploited).

The primary motivation for this design is to enable companies, token issuers, and other entities to reduce onboarding friction for end users by covering transaction fees and reserve requirements on their behalf. Today, users must self-fund both, or companies must essentially donate XRP to users with no controls over how they use it, before interacting with the XRPL. This creates a barrier to entry for use cases such as token distribution, NFT minting, or enterprise onboarding. Sponsorship provides a mechanism for entities with established XRP balances to subsidize these costs while maintaining strong on-chain accountability.

3. Overview¶

Accounts can include signatures from sponsors in their transactions that will allow the sponsors to pay the transaction fee for the transaction, and/or the reserve for any accounts/objects created in the transaction.

Sponsors can also pre-fund fees or reserves, if they do not want to deal with the burden of co-signing every sponsored transaction.

We propose:

• Modifying the ledger entry common fields
• Creating the Sponsorship ledger entry
• Modifying the AccountRoot ledger entry
• Modifying the RippleState ledger entry
• Modifying the transaction common fields
• Creating the SponsorshipSet transaction type
• Creating the SponsorshipTransfer transaction type
• Modifying the Payment transaction type (only flags)
• Modifying the AccountDelete transaction type (behavior only, not fields)
• Adding two additional granular permissions (SponsorFee, SponsorReserve)

In addition, there will be a modification to the account_objects RPC method, and a new Clio RPC method called account_sponsoring.

This feature will require an amendment, tentatively titled Sponsor.

3.1. Terminology¶

• Sponsor: The account that is covering the reserve or paying the transaction fee on behalf of another account.
• Sponsee: The account that the sponsor is paying a transaction fee or reserve on behalf of.
• Owner: The account that owns a given object (or the account itself). This is often the same as the sponsee.
• Sponsored account: An account that a sponsor is covering the reserve for (currently priced at 1 XRP).
• Sponsored object: A non-account ledger object that a sponsor is covering the reserve for (currently priced at 0.2 XRP).
• Sponsor relationship: The relationship between a sponsor and sponsee.
• Sponsorship type: The "type" of sponsorship - sponsoring transaction fees vs. sponsoring reserves.

3.2. The Sponsorship Flow (Not Pre-Funded)¶

In this scenario, the sponsor, Spencer, wants to pay the transaction fee and/or reserve for the sponsee Alice's transaction.

• Alice constructs her transaction and autofills it (so that all fields, including the fee and sequence number, are included in the transaction). She adds Spencer's account and sponsorship type to the transaction as well.
• Spencer signs the transaction and provides his signature to Alice.
• Alice adds Spencer's public key and signature to her transaction.
• Alice signs and submits her transaction as normal.

3.3. The Sponsorship Flow (Pre-Funded)¶

In this scenario, the sponsor, Spencer, wants to pay the transaction fee and/or reserve for the sponsee Alice's transaction, but would prefer to pre-fund the XRP necessary, so that he does not have to co-sign every single one of Alice's transactions.

• Spencer submits a transaction to initialize the sponsorship relationship and pre-fund Alice's sponsorship (note: these funds are not sent directly to Alice. She may only use the allocated funds for fees and reserves, and these are separate buckets).
• Alice does not need to do anything to accept this.
• Alice constructs her transaction and autofills it (so that all fields, including the fee and sequence number, are included in the transaction). She adds Spencer's account and sponsorship type to the transaction as well.
• Alice signs and submits her transaction as normal.

Note that Spencer does not need to be a part of Alice's signing and submission flow in this example.

3.4. Recouping a Sponsored Object Reserve¶

In this scenario, the sponsor, Spencer, would like to re-obtain the reserve that is currently trapped due to his sponsorship of Alice's object.

Spencer can submit a SponsorshipTransfer transaction, which allows him to pass the onus of the reserve back to Alice, or pass it onto another sponsor.

3.5. Recouping a Sponsored Account Reserve¶

In this scenario, the sponsor, Spencer, would like to retrieve his reserve from sponsoring Alice's account.

There are two ways in which he could do this:

• If Alice is done using her account, she can submit an AccountDelete transaction, which will send all remaining funds in the account back to Spencer.
• If Alice would like to keep using her account, or would like to switch to a different provider, she (or Spencer) can submit a SponsorshipTransfer transaction to either remove sponsorship or transfer it to the new provider.

4. Ledger Entries: Common Fields¶

This section describes the changes to the common fields of ledger entries, to indicate whether or not they are sponsored, and if so, who the sponsor is.

4.1. Fields¶

As a reference, here are the fields that all ledger objects currently have:

This spec proposes one additional field:

4.2. Ownership¶

Any sponsored object is still owned by the original owner, and the sponsor is not added as an additional owner.

4.3. Invariant Checks¶

4.3.1. Allowed Ledger Entry Types¶

The Sponsor field may appear on the following ledger entry types:

• AccountRoot (for account reserve sponsorship)
• Offer
• Escrow
• Check
• PayChannel
• DepositPreauth
• Ticket
• NFTokenPage
• NFTokenOffer
• AMM
• Bridge
• XChainOwnedClaimID
• XChainOwnedCreateAccountClaimID
• DID
• Any other ledger entry type that contributes to an account's owner reserve, subject to implementation details

The Sponsor field must not appear on:

• RippleState objects (they instead use the HighSponsor and LowSponsor fields defined in section 7.1)
• DirectoryNode objects (these do not have reserves)
• Amendments objects (global ledger objects)
• FeeSettings objects (global ledger objects)
• NegativeUNL objects (global ledger objects)

4.3.2. Constraints¶

• The field must be omitted when there is no sponsor.
• When present, the field must contain a valid AccountID that exists on the ledger.
• The field is added when sponsorship is established (either at object creation or via SponsorshipTransfer).
• The field is removed when sponsorship is dissolved via SponsorshipTransfer.
• The Sponsor must have a SponsoringOwnerCount that is greater than 0.
• The Sponsor value must differ from the object's owner (as indicated by the Owner or Account field). An account may not sponsor its own objects.
• The sponsor account must have sufficient XRP to meet its reserve requirements when creating/sponsoring new objects, including reserves for all objects and accounts it sponsors.

NOTE: A sponsor may also be a sponsee.

4.3.4. Authoritative Indication¶

The presence or absence of Sponsor is the authoritative indication of whether an object is sponsored for reserves. The presence of this field triggers the following behaviors:

• The object's reserve is counted against the sponsor's SponsoringOwnerCount (or SponsoringAccountCount for AccountRoot), not the owner's OwnerCount.
• The sponsor's SponsoringOwnerCount (or SponsoringAccountCount for AccountRoot) is incremented.
• The owner's SponsoredOwnerCount is incremented (for non-AccountRoot objects).
• The reserve calculation for both sponsor and owner accounts is adjusted accordingly.

NOTE: These values are likely not recalculated later due to performance issues, and the implementation should make sure that the SponsoringOwnerCount, SponsoredOwnerCount, and SponsoringAccountCount fields in all accounts are updated appropriately. The accuracy will only be verifiable via off-chain mechanisms.

5. Ledger Entry: Sponsorship¶

Sponsorship is an object that reflects a sponsoring relationship between two accounts, Sponsor and Sponsee. This allows sponsors to "pre-fund" sponsees, if they so desire.

Note: this object does not need to be created in order to sponsor accounts. It is an offered convenience, so that sponsors do not have to co-sign every sponsored transaction if they don't want to, especially for transaction fees. It also allows them to set a maximum balance even if they still want to co-sign transactions.

5.1. Object Identifier¶

5.1.1. Key Space¶

The Sponsorship ledger entry uses a dedicated key space constant spaceSponsorship, which will be assigned a unique 16-bit value during implementation (e.g., 0x0053 or another available value in the key space range).

5.1.2. ID Calculation Algorithm¶

The unique identifier for a Sponsorship object is calculated using SHA512-Half of the following values concatenated in order:

1. The Sponsorship space key ('>')
2. The AccountID of the Owner (sponsor)
3. The AccountID of the Sponsee

This ensures that there can be at most one Sponsorship object per sponsor-sponsee pair, preventing duplicate relationships.

5.2. Fields¶

5.3. Flags¶

There are two flags on this object:

5.4. Ownership¶

The object is owned by Owner, who also pays the reserve for this object.

5.5. Reserves¶

Reserve Requirement: Standard

The reserve is charged to the sponsor's account (the Owner field).

5.6. Deletion¶

5.6.1. Deletion Transactions¶

SponsorshipSet with the tfDeleteObject flag

5.6.2. Deletion Conditions¶

• The SponsorshipSet transaction must be submitted by the sponsor (the Owner of the Sponsorship object).
• The tfDeleteObject flag must be enabled.
• No other fields (FeeAmount, MaxFee, ReserveCount, or flag-setting fields) may be specified in the deletion transaction.
• Note: Non-zero FeeAmount and ReserveCount values are permitted at deletion time. Any remaining XRP in FeeAmount is returned to the sponsor's account upon deletion.

5.6.3. Account Deletion Blocker¶

This object is a deletion blocker.

This object must be deleted before its owner account (the sponsor) can be deleted. The sponsor must either:

1. Delete the Sponsorship object via SponsorshipSet with tfDeleteObject, or
2. Wait for the sponsee to delete it (if the sponsee has permission to do so)

Note on Existing Sponsored Objects: Deleting a Sponsorship object does not affect already-sponsored ledger entries or accounts. Those existing sponsored objects/accounts will retain their Sponsor field and continue to be sponsored. To dissolve sponsorship for existing objects, the SponsorshipTransfer transaction must be used.

5.7. Invariants¶

The following invariants must always hold for a Sponsorship object:

• Owner != Sponsee (an account cannot create a Sponsorship object with itself as both sponsor and sponsee)
• FeeAmount >= 0 AND FeeAmount is denominated in XRP (drops)
• ReserveCount >= 0
• At least one of FeeAmount and ReserveCount must be included
• Both Owner and Sponsee must be valid AccountID values that exist on the ledger

NOTE: The invariants in 4.3 also apply to Sponsorship objects, as they apply to all objects.

5.8. RPC Name¶

The snake_case form of the ledger object name is sponsorship.

5.9. Example JSON¶

{
  "LedgerEntryType": "Sponsorship",
  "Owner": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf",
  "Sponsee": "rfkDkFai4jUfCvAJiZ5Vm7XvvWjYvDqeYo",
  "FeeAmount": "1000000", // 1 XRP, 1 million drops
  "MaxFee": "1000", // 1000 drops
  "ReserveCount": 5,
  "Flags": 0,
  "OwnerNode": "0000000000000000",
  "SponseeNode": "0000000000000000",
  "PreviousTxnID": "1234567890ABCDEF1234567890ABCDEF1234567890ABCDEF1234567890ABCDEF",
  "PreviousTxnLgrSeq": 12345678
}

6. Ledger Entry: AccountRoot¶

An AccountRoot ledger entry type describes a single account, its settings, and XRP balance.

6.1. Fields¶

As a reference, here are the fields that the AccountRoot ledger object currently has.

This spec proposes these additional fields:

6.1.1. Sponsor¶

The Sponsor field is already added in the ledger common fields (see section 4.1), but it has some additional rules associated with it on the AccountRoot object.

This field is included if the account was created with a sponsor paying its account reserve. If this sponsored account is deleted, the destination of the AccountDelete transaction must equal Sponsor, so that the sponsor can recoup their fees.

Note: The Destination field of AccountDelete will still work as-is if the account is not sponsored, where it can be set to any account.

6.2. Account Reserve Calculation¶

The existing reserve calculation is:

$$ acctReserve + objReserve * acct.OwnerCount $$

The total account reserve should now be calculated as:

$$ \displaylines{ (acct.Sponsor \text{ ? } 0 : acctReserve) + objReserve * (acct.OwnerCount + acct.SponsoringOwnerCount - acct.SponsoredOwnerCount) + acctReserve * acct.SponsoringAccountCount } $$

6.3. Invariants¶

The following invariants must hold for AccountRoot objects with sponsorship fields:

• SponsoredOwnerCount <= OwnerCount (cannot have more sponsored objects than total owned objects)
• If Sponsor is present, it must be a valid AccountID that exists on the ledger
• The reserve calculation must always result in a non-negative value
• The Sponsor's SponsoringAccountCount must be greater than 0

Global Invariant (referenced in section 18.2):

Across all accounts in the ledger: $$\sum_{accounts} SponsoredOwnerCount = \sum_{accounts} SponsoringOwnerCount$$

This ensures that every sponsored object is properly accounted for on both the sponsee and sponsor sides.

6.4. Example JSON¶

{
  "LedgerEntryType": "AccountRoot",
  "Account": "rfkDkFai4jUfCvAJiZ5Vm7XvvWjYvDqeYo",
  "Balance": "100000000", // 100 XRP, in drops
  "OwnerCount": 5,
  "Sponsor": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf",
  "SponsoredOwnerCount": 2,
  "SponsoringOwnerCount": 1,
  "SponsoringAccountCount": 1,
  "PreviousTxnID": "1234567890ABCDEF1234567890ABCDEF1234567890ABCDEF1234567890ABCDEF",
  "PreviousTxnLgrSeq": 12345679
}

7. Ledger Entry: RippleState¶

A RippleState ledger entry represents a trust line between two accounts. Each account can change its own limit and other settings, but the balance is a single shared value. A trust line that is entirely in its default state is considered the same as a trust line that does not exist and is automatically deleted. You can create or modify a trust line with a TrustSet transaction.

7.1. Fields¶

As a reference, here are the fields that the RippleState ledger object currently has.

This spec proposes these additional fields:

These additional fields are necessary for a trustline since the reserve for this object may be held by two accounts (in the case of a bidirectional trustline).

7.2. Invariants¶

Existing invariants remain.

• The common field Sponsor must not be on any RippleState objects (they must use HighSponsor and LowSponsor instead).
• If LowSponsor is included, lsfLowReserve must be enabled.
• If HighSponsor is included, lsfHighReserve must be enabled.

NOTE: The invariants in 4.3 also apply to RippleState objects, as they apply to all objects.

7.3. Example JSON¶

{
  "LedgerEntryType": "RippleState",
  "Balance": {
    "currency": "USD",
    "issuer": "rLowAccountAddressXXXXXXXXXXXXXXX",
    "value": "-10"
  },
  "HighLimit": {
    "currency": "USD",
    "issuer": "rHighAccountAddressXXXXXXXXXXXXXX",
    "value": "100"
  },
  "LowLimit": {
    "currency": "USD",
    "issuer": "rLowAccountAddressXXXXXXXXXXXXXXX",
    "value": "0"
  },
  "HighSponsor": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf",
  "LowSponsor": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf",
  "Flags": 262144,
  "HighNode": "0000000000000000",
  "LowNode": "0000000000000000",
  "PreviousTxnID": "ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789",
  "PreviousTxnLgrSeq": 12345680
}

8. Transactions: Common Fields¶

8.1. Fields¶

As a reference, here are the fields that all transactions currently have.

We propose these modifications:

8.1.1. SponsorFlags¶

The SponsorFlags field allows the user to specify which sponsorship type(s) they wish to participate in. This field must be included if the Sponsor field is included in a transaction, and at least one flag must be specified if the Sponsor field is included in a transaction. The SponsorFlags field must not be included if the Sponsor field is not included in a transaction.

There are two flag values that are supported:

8.1.2 SponsorSignature¶

8.1.2.1. SigningPubKey, TxnSignature and Signers¶

Either TxnSignature or Signers must be included in the final transaction.

There will be no additional transaction fee required for the use of the TxnSignature field.

TxnSignature and Signers will not be signing fields (they will not be included in transaction signatures, though they will still be included in the stored transaction).

Either SigningPubKey+TxnSignature or Signers must be included in the transaction. There is one exception to this: if lsfRequireSignatureForFee/lsfRequireSignatureForReserve are not enabled for the type(s) of sponsorship in the transaction.

8.2. Transaction Fee¶

If the SponsorSignature.Signers field is necessary, then the total fee of the transaction will be increased, due to the extra signatures that need to be processed. This is similar to the additional fees for multisigning. The minimum fee will be $(|signatures|+1)*base\textunderscore fee$.

The total fee calculation for signatures will now be $( 1+|tx.Signers| + |tx.SponsorSignature.Signers|) * base\textunderscore fee$ (plus transaction-specific fees).

8.3. Failure Conditions¶

8.3.1. General Failures¶

1. SponsorSignature.TxnSignature is invalid.
2. SponsorSignature.Signers is invalid (the signer list isn't on the account, quorum isn't reached, the public key(s) are invalid, or signature(s) are invalid).
3. SponsorSignature.SigningPubKey is invalid (the public key doesn't match the account's master key or regular key, or the public key is otherwise invalid).
4. The Sponsor doesn't exist on the ledger.
5. An invalid sponsorship flag is used.
6. SponsorSignature.SigningPubKey, SponsorSignature.TxnSignature, and SponsorSignature.Signers are all included (or other incorrect combinations of signing fields).
7. Sponsor, SponsorFlags, or SponsorSignature is included in a transaction that does not support sponsorship (see section 8.3.4).
8. Only one or two of Sponsor, SponsorFlags, and SponsorSignature is included (they must either all be included, if the transaction is sponsored, or none, if it is not).
9. SponsorFlags includes invalid flags (currently, the only two valid flags are tfSponsorFee and tfSponsorReserve).

8.3.2. Fee Sponsorship Failures¶

1. The sponsor's account does not have enough XRP to cover the sponsored transaction fee (telINSUF_FEE_P)

If a Sponsorship object exists:

1. The lsfRequireSignatureForFee flag is enabled and there is no sponsor signature included.
2. There is not enough XRP in the FeeAmount to pay for the transaction.
3. Paying fees via sponsorship will not be able to go below the reserve requirement.
4. The fee in tx.Fee is greater than Sponsorship.MaxFee

If a Sponsorship object does not exist:

1. There is no sponsor signature included.

Note: if a transaction doesn't charge a fee (such as an account's first SetRegularKey transaction), the transaction will still succeed.

8.3.3. Reserve Sponsorship Failures¶

1. The sponsor does not have enough XRP to cover the reserve (tecINSUFFICIENT_RESERVE)
2. The transaction does not support reserve sponsorship (see section 8.3.4)

If a Sponsorship object exists:

1. The lsfRequireSignatureForReserve flag is enabled and there is no sponsor signature included.
2. There is not enough remaining count in the ReserveCount to pay for the transaction.

If a Sponsorship object does not exist:

1. There is no sponsor signature included.

Note: if a transaction doesn't charge a reserve (such as AccountSet), the transaction will still succeed.

8.3.4. Transactions that cannot be sponsored¶

All transactions (other than pseudo-transactions) may use the tfSponsorFee flag, since they all have a fee.

However, some transactions will not support the tfSponsorReserve flag.

• Batch transactions
• Batch does not create any objects on its own, and therefore its use in the outer transaction would be confusing, as users may think that that means that all inner transactions are sponsored. The inner transactions should use tfSponsorReserve instead.
• All pseudo-transactions (currently EnableAmendment, SetFee, and UNLModify)
• The fees and reserves for those objects are covered by the network, not by any one account.

Also, many transactions, such as AccountSet, will have no change in output when using the tfSponsorReserve flag, if they do not create any new objects or accounts.

8.4. State Changes¶

8.4.1. Fee Sponsorship State Changes¶

If a Sponsorship object exists, the tx.Fee value is decremented from the Sponsorship.FeeAmount.

If a Sponsorship object does not exist, the tx.Fee value is decremented from the sponsor's AccountRoot.Balance.

8.4.2. Reserve Sponsorship State Changes¶

Any account/object that is created as a part of the transaction will have a Sponsor field.

The sponsor's SponsoringOwnerCount field will be incremented by the number of objects that are sponsored as a part of the transaction, and the SponsoringAccountCount field will be incremented by the number of new accounts that are sponsored as a part of the transaction.

The sponsee's SponsoredOwnerCount field will be incremented by the number of objects that are sponsored as a part of the transaction.

The SponsoredOwnerCount, SponsoringOwnerCount, and SponsoringAccountCount fields will be decremented when those objects/accounts are deleted.

9. Transaction: SponsorshipSet¶

This transaction creates, updates, and deletes the Sponsorship object.

9.1. Fields¶

9.2. Flags¶

9.3. Transaction Fee¶

Fee Structure: Standard

This transaction uses the standard transaction fee (currently 10 drops, subject to Fee Voting changes).

9.4. Failure Conditions¶

1. tx.Account is not equal to either tx.Sponsor or tx.Sponsee (temMALFORMED)
2. Both Sponsor and Sponsee are specified (temMALFORMED)
3. Neither Sponsor nor Sponsee is specified (temMALFORMED)
4. Sponsor is specified (which means that the Sponsee is submitting the transaction) and tfDeleteObject is not enabled, as only the sponsor can create/update the Sponsorship object (temMALFORMED)
5. MaxFee is less than the base fee or is not denominated in XRP (temBAD_AMOUNT)
6. MaxFee is greater than FeeAmount (temBAD_AMOUNT)
7. FeeAmount is not denominated in XRP (temBAD_AMOUNT)
8. Sponsor or Sponsee does not exist on the ledger (terNO_ACCOUNT)
9. Owner == Sponsee (attempting to create self-sponsorship) (temMALFORMED)
10. Sponsor does not have sufficient XRP to cover the reserve for the Sponsorship object (tecINSUFFICIENT_RESERVE)
11. If tfDeleteObject is enabled:
12. FeeAmount is specified (temMALFORMED)
13. MaxFee is specified (temMALFORMED)
14. ReserveCount is specified (temMALFORMED)
15. tfSponsorshipSetRequireSignForFee is enabled (temINVALID_FLAG)
16. tfSponsorshipSetRequireSignForReserve is enabled (temINVALID_FLAG)
17. tfSponsorshipClearRequireSignForFee is enabled (temINVALID_FLAG)
18. tfSponsorshipClearRequireSignForReserve is enabled (temINVALID_FLAG)
19. The Sponsorship object does not exist (tecNO_ENTRY)

9.5. State Changes¶

If creating a new Sponsorship object:

• Create the Sponsorship ledger entry with the specified fields
• Increment the sponsor's OwnerCount by 1
• Add the object to both the sponsor's and sponsee's owner directories
• Deduct the object reserve from the sponsor's available XRP

If updating an existing Sponsorship object:

• Update Sponsorship.FeeAmount to tx.FeeAmount (or 0 if omitted)
• Update Sponsorship.MaxFee to tx.MaxFee (or remove field if omitted)
• Update Sponsorship.ReserveCount to tx.ReserveCount (or 0 if omitted)
• Update flags based on tfSponsorshipSetRequireSignForFee, tfSponsorshipClearRequireSignForFee, tfSponsorshipSetRequireSignForReserve, and tfSponsorshipClearRequireSignForReserve
• If FeeAmount is increased, deduct the additional XRP from the sponsor's balance
• If FeeAmount is decreased, return the difference to the sponsor's balance

If deleting the Sponsorship object (tfDeleteObject flag):

• Delete the Sponsorship ledger entry
• Return all remaining XRP in FeeAmount to the sponsor's balance
• Decrement the sponsor's OwnerCount by 1
• Remove the object from both the sponsor's and sponsee's owner directories
• Return the object reserve to the sponsor's available XRP

Note: Deleting a Sponsorship object does not affect already-sponsored ledger entries or accounts. Those existing sponsored objects/accounts will retain their Sponsor field and continue to be sponsored. To dissolve sponsorship for existing objects, the SponsorshipTransfer transaction must be used.

9.6. Example JSON¶

{
  "TransactionType": "SponsorshipSet",
  "Account": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf",
  "Sponsee": "rfkDkFai4jUfCvAJiZ5Vm7XvvWjYvDqeYo",
  "FeeAmount": "1000000",
  "MaxFee": "1000",
  "ReserveCount": 5,
  "Fee": "12",
  "Sequence": 42
}

10. Transaction: SponsorshipTransfer¶

This transaction transfers a sponsor relationship for a particular ledger object's reserve. The sponsor relationship can either be passed on to a new sponsor, or dissolved entirely (with the sponsee taking on the reserve). Either the sponsor or sponsee may submit this transaction at any point in time.

There are three valid transfer scenarios:

• Transferring from sponsor to sponsee (sponsored to unsponsored)
• Either the sponsor or sponsee may submit this transaction. Both have the right to end the relationship on that object at any time.
• Transferring from sponsee to sponsor (unsponsored to sponsored)
• Only the sponsee may submit this transaction. It follows a standard sponsoring flow in terms of signing.
• Transferring from sponsor to new sponsor
• Only the sponsee may submit this transaction. The old sponsor is not directly involved, and the new sponsor provides their signature via the standard signing flow.

10.1. Fields¶

10.1.1. ObjectID¶

This field should be included if this transaction is dealing with sponsored object, rather than on a sponsored account. This field indicates which object the relationship is changing for.

If it is not included, then it refers to the account sending the transaction.

10.1.2. Sponsor¶

The Sponsor field is already added in the transaction common fields (see section 6.1.1), but it has some additional rules associated with it on the SponsorshipTransfer transaction.

In this case, if Sponsor is included with the tfSponsorReserve flag, then the reserve sponsorship for the provided object will be transferred to the Sponsor instead of passing back to the ledger object's owner.

If there is no Sponsor field, or if the tfSponsorReserve flag is not included, then the burden of the reserve will be passed back to the ledger object's owner (the former sponsee).

10.2. Sponsorship Transfer Scenarios¶

10.2.1. Transferring from Sponsor to Sponsee (Sponsored to Unsponsored)¶

This scenario ends the sponsorship for a sponsored ledger object or account. The sponsor and sponsee both have the right to end the relationship at any time.

The following fields indicate this scenario:

• ObjectID must be included (if sponsored object)
• Sponsor must be excluded
• SponsorFlags.tfSponsorReserve must be excluded
• The object specified by ObjectID must be have a Sponsor field

10.2.2. Transferring from Sponsee to Sponsor (Unsponsored to Sponsored)¶

This scenario sponsors an object or account that was not previously sponsored. Only the sponsee can submit this transaction.

The following fields indicate this scenario:

• ObjectID must be included (if sponsored object)
• Sponsor must be included
• SponsorFlags.tfSponsorReserve must be included
• The object specified by ObjectID must not have a Sponsor field

10.2.3. Transferring from Sponsor to New Sponsor¶

This scenario migrates the sponsorship for a sponsored object or account to a new sponsor. Only the sponsee can submit this transaction.

The following fields indicate this scenario:

• ObjectID must be included (if sponsored object)
• Sponsor must be included
• SponsorFlags.tfSponsorReserve must be included
• The object specified by ObjectID must have a Sponsor field

NOTE: The only difference between this scenario and the one specified in 10.2.2 is that in this case, the object specified by ObjectID must already have a Sponsor field.

10.2.4. Sponsorship Transfer for Accounts¶

The same 3 scenarios above apply to accounts as well. The only difference is that for accounts, the ObjectID field is not included, and instead the Account field is used to specify which account the sponsorship is changing for.

10.3. Transaction Fee¶

Fee Structure: Standard

This transaction uses the standard transaction fee (currently 10 drops, subject to Fee Voting changes).

10.4. Failure Conditions¶

All failure conditions mentioned in section 8.3 still apply here.

Additional failure conditions specific to SponsorshipTransfer:

1. ObjectID is specified but does not exist on the ledger (tecNO_TARGET)
2. ObjectID is specified but does not have a Sponsor field (object is not sponsored) (tecNO_PERMISSION)
3. ObjectID is not specified and the tx.Account does not have a Sponsor field (account is not sponsored) (tecNO_PERMISSION)
4. tx.Account is neither the current sponsor nor the owner (sponsee) of the object/account specified by ObjectID (tecNO_PERMISSION)
5. If dissolving the sponsorship (no Sponsor field or tfSponsorReserve flag not set):
6. The owner does not have enough XRP to cover the reserve for this object/account (tecINSUFFICIENT_RESERVE)
7. If creating a new sponsorship (unsponsored to sponsored):
8. The transaction is not submitted by the sponsee (tecNO_PERMISSION)
9. The Sponsor field or the SponsorFlags field is missing (temMALFORMED)
10. The SponsorFlags field does not include the tfSponsorReserve flag (temINVALID_FLAG)
11. The new sponsor account does not exist (terNO_ACCOUNT)
12. The new sponsor does not have enough XRP to cover the reserve for this object/account (tecINSUFFICIENT_RESERVE)
13. If transferring the sponsorship to a new sponsor:
14. The transaction is not submitted by the sponsee (tecNO_PERMISSION)
15. The Sponsor field or the SponsorFlags field is missing (temMALFORMED)
16. The SponsorFlags field does not include the tfSponsorReserve flag (temINVALID_FLAG)
17. The new sponsor account does not exist (terNO_ACCOUNT)
18. The new sponsor does not have enough XRP to cover the reserve for this object/account (tecINSUFFICIENT_RESERVE)

10.5. State Changes¶

• The Sponsor field on the object specified by ObjectID is deleted if the tx.Sponsor is the object's Owner, otherwise the Sponsor field is updated to the new tx.Sponsor.
• The old sponsor (if applicable) has its SponsoringOwnerCount/SponsoringAccountCount decremented by one.
• The new sponsor (if applicable) has its SponsoringOwnerCount/SponsoringAccountCount incremented by one.
• If there is no new sponsor, then the owner's SponsoredOwnerCount will be decremented by one.

10.6. Example JSON¶

{
  "TransactionType": "SponsorshipTransfer",
  "Account": "rfkDkFai4jUfCvAJiZ5Vm7XvvWjYvDqeYo",
  "ObjectID": "13F1A9B5C2D3E4F613F1A9B5C2D3E4F613F1A9B5C2D3E4F613F1A9B5C2D3E4F6",
  "Sponsor": "rNEWSponsor3LNcTz8JF2oJC6qaww6RZ7Lw",
  "SponsorFlags": 2,
  "Fee": "12",
  "Sequence": 43
}

11. Transaction: Payment¶

A Payment transaction represents a transfer of value from one account to another. (Depending on the path taken, this can involve additional exchanges of value, which occur atomically.) This transaction type can be used for several types of payments.

Payments are also the only way to create accounts.

As a reference, here are the fields that Payment currently has.

11.1. Fields¶

This amendment proposes no changes to the fields, only to the flags and behavior.

11.2. Flags¶

As a reference, here are the flags that Payment currently has:

This spec proposes the following additions:

11.3. Failure Conditions¶

Existing failure conditions still apply (see Payment documentation), with one exception:

1. If tfSponsorCreatedAccount is enabled, the XRP amount does not need to be greater than or equal to the account reserve requirement.

Additional failure conditions when tfSponsorCreatedAccount is enabled:

1. tfNoRippleDirect, tfPartialPayment, or tfLimitQuality are enabled (temINVALID_FLAG)
2. Amount specifies a non-XRP currency (temBAD_AMOUNT)
3. Destination already exists (tecNO_SPONSOR_PERMISSION)
4. Account does not have enough XRP to cover the account reserve requirement (tecNO_DST_INSUF_XRP)

11.4. State Changes¶

Existing state changes still apply (see Payment documentation).

If tfSponsorCreatedAccount is enabled, the created account's AccountRoot will have a Sponsor field pointing to the tx.Account.

11.5. Example JSON¶

{
  "TransactionType": "Payment",
  "Account": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf",
  "Destination": "rfkDkFai4jUfCvAJiZ5Vm7XvvWjYvDqeYo", // the new sponsored account
  "Amount": "1", // 1 drop, the minimum
  "Flags": 524288, // tfSponsorCreatedAccount
  "Fee": "10",
  "Sequence": 3
}

12. Transaction: AccountDelete¶

This transaction deletes an account.

As a reference, here are the fields that AccountDelete currently has.

12.1. Fields¶

This amendment proposes no changes to the fields, only to the behavior.

12.2. Failure Conditions¶

Existing failure conditions still apply (see AccountDelete documentation).

Additional failure conditions for sponsored accounts:

1. If the AccountRoot associated with tx.Account has a Sponsor field:

2. The Destination is not equal to AccountRoot.Sponsor (tecNO_PERMISSION - sponsored account funds must go to sponsor)

3. If the AccountRoot associated with tx.Account has a non-zero SponsoringOwnerCount or SponsoringAccountCount field:

4. The transaction fails with tecHAS_OBLIGATIONS (account is currently sponsoring other accounts or objects and cannot be deleted until those sponsorships are transferred or dissolved)

12.3. State Changes¶

Existing state changes still apply, including rules around deletion blockers.

If the AccountRoot associated with the tx.Account has a Sponsor field, the Sponsor's AccountRoot.SponsoringAccountCount is decremented by 1.

If the AccountRoot associated with the tx.Account has a SponsoredOwnerCount field, the Sponsor's SponsoringOwnerCount is decremented by the tx.Account's SponsoredOwnerCount.

12.4. Example JSON¶

{
  "TransactionType": "AccountDelete",
  "Account": "rWYkbWkCeg8dP6rXALnjgZSjjLyih5NXm",
  "Destination": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf", // the sponsor
  "Fee": "5000000",
  "Sequence": 2470665
}

13. Granular Permission: SponsorFee¶

13.1. Description¶

The SponsorFee permission allows an account to delegate its ability to sponsor other accounts' transaction fees.

13.2. Transaction Types Affected¶

This permission affects all transaction types that support the Sponsor field (see section 8.3.4).

When a transaction includes a Sponsor field with the tfSponsorFee flag enabled, the sponsor must have granted the SponsorFee permission to the transaction submitter (the tx.Account), unless:

• The sponsor is signing the transaction directly (via SponsorSignature.SigningPubKey and SponsorSignature.TxnSignature or SponsorSignature.Signers), OR
• A Sponsorship object exists between the sponsor and sponsee with sufficient FeeAmount

13.3. Permission Value¶

65549

14. Granular Permission: SponsorReserve¶

14.1. Description¶

The SponsorFee permission allows an account to delegate its ability to sponsor other accounts' transaction fees.

14.2. Transaction Types Affected¶

This permission affects all transaction types that support the Sponsor field (see section 8.3.4) and create new ledger objects or accounts.

When a transaction includes a SponsorFlags field with the tfSponsorReserve flag enabled, the sponsor must have granted the SponsorReserve permission to the transaction submitter (the tx.Account), unless:

• The sponsor is signing the transaction directly (via SponsorSignature.SigningPubKey and SponsorSignature.TxnSignature or SponsorSignature.Signers), OR
• A Sponsorship object exists between the sponsor and sponsee with sufficient ReserveCount

14.3. Permission Value¶

65550

15. RPC: account_objects¶

The account_objects RPC method already exists on the XRPL. This spec proposes an addition to the account_objects RPC method, to better support sponsored accounts.

15.1. Request Fields¶

As a reference, here are the fields that account_objects currently accepts.

15.2. Response Fields¶

The response fields remain the same.

15.3. Failure Conditions¶

There are no additional failure conditions.

15.4. Example Request¶

{
  "command": "account_objects",
  "account": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf",
  "sponsored": true,
  "ledger_index": "validated",
  "type": "state"
}

15.5. Example Response¶

{
  "account": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf",
  "account_objects": [
    {
      "Balance": {
        "currency": "USD",
        "issuer": "rrrrrrrrrrrrrrrrrrrrBZbvji",
        "value": "100"
      },
      "Flags": 65536,
      "HighLimit": {
        "currency": "USD",
        "issuer": "rN7n7otQDd6FczFgLdlqtyMVrn3HMfXpf",
        "value": "1000"
      },
      "HighNode": "0000000000000000",
      "HighSponsor": "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
      "LedgerEntryType": "RippleState",
      "LowLimit": {
        "currency": "USD",
        "issuer": "rfkDkFai4jUfCvAJiZ5Vm7XvvWjYvDqeYo",
        "value": "0"
      },
      "LowNode": "0000000000000000",
      "PreviousTxnID": "1234567890ABCDEF1234567890ABCDEF1234567890ABCDEF1234567890ABCDEF",
      "PreviousTxnLgrSeq": 12345678,
      "index": "ABCDEF1234567890ABCDEF1234567890ABCDEF1234567890ABCDEF1234567890"
    }
  ],
  "ledger_hash": "FEDCBA0987654321FEDCBA0987654321FEDCBA0987654321FEDCBA0987654321",
  "ledger_index": 56789012,
  "validated": true
}

16. RPC: account_sponsoring¶

The account_sponsoring RPC method is used to fetch a list of objects that an account is sponsoring; namely, a list of objects where the Sponsor is the given account. It has a very similar API to the account_objects method.

[NOTE: This API will not be implemented in rippled, but will instead be implemented in Clio. This is due to the fact that this API would likely require another database to keep track of the sponsorship relationships, which would be too expensive to maintain in rippled.]

16.1. Request Fields¶

16.2. Response Fields¶

The response fields are nearly identical to account_objects.

16.3. Failure Conditions¶

1. Any of the universal error types.
2. invalidParams - One or more fields are specified incorrectly, or one or more required fields are missing.
3. actNotFound - The address specified in the account field of the request does not correspond to an account in the ledger.
4. lgrNotFound - The ledger specified by the ledger_hash or ledger_index does not exist, or it does exist but the server does not have it.

16.4. Example Request¶

{
  "command": "account_sponsoring",
  "account": "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
  "ledger_index": "validated",
  "limit": 10
}

16.5. Example Response¶

{
  "account": "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
  "sponsored_objects": [
    {
      "Balance": {
        "currency": "USD",
        "issuer": "rrrrrrrrrrrrrrrrrrrrBZbvji",
        "value": "100"
      },
      "Flags": 65536,
      "HighLimit": {
        "currency": "USD",
        "issuer": "rSponsee1ABC123XYZ456DEF789GHI",
        "value": "1000"
      },
      "HighNode": "0000000000000000",
      "HighSponsor": "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
      "LedgerEntryType": "RippleState",
      "LowLimit": {
        "currency": "USD",
        "issuer": "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
        "value": "0"
      },
      "LowNode": "0000000000000000",
      "PreviousTxnID": "E3FE6EA3D48F0C2B639448020EA4F03D4F4F8FFDB243A852A0F59177921B4879",
      "PreviousTxnLgrSeq": 14090896,
      "index": "9ED4406351B7A511A012A9B5E7FE4059FA2F7650621379C0013492C315E25B97"
    },
    {
      "Account": "rSponsee2XYZ789ABC123DEF456GHI",
      "Balance": "1000000",
      "Flags": 0,
      "LedgerEntryType": "AccountRoot",
      "OwnerCount": 3,
      "PreviousTxnID": "0D5FB50FA65C9FE1538FD7E398FFFE9D1908DFA4576D8D7A020040686F93C77D",
      "PreviousTxnLgrSeq": 14091574,
      "Sequence": 1,
      "Sponsor": "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
      "index": "13F1A95D7AAB7108D5CE7EEAF504B2894B8C674E6D68499076441C4837282BF8"
    },
    {
      "LedgerEntryType": "Sponsorship",
      "Owner": "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
      "Sponsee": "rSponsee3DEF456GHI789ABC123XYZ",
      "FeeAmount": "5000000",
      "MaxFee": "10000",
      "ReserveCount": 5,
      "OwnerNode": "0000000000000000",
      "SponseeNode": "0000000000000000",
      "PreviousTxnID": "B044D3861WL1HZ4WM4GURZVKTTdJPgM1v5T8QBKWJZQM",
      "PreviousTxnLgrSeq": 14091600,
      "index": "2B42F8F4E3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3"
    }
  ],
  "ledger_hash": "4C99E5F63C0D0B1C2283D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3D3",
  "ledger_index": 14091625,
  "validated": true
}

17. Security Considerations¶

17.1. Security Axioms¶

Both the sponsee and the sponsor must agree to enter into a sponsor relationship. The sponsee must actively consent to the sponsor handling the reserve, and the sponsor must be willing to take on that reserve. A signature from both parties ensures that this is the case.

A sponsor will never be stuck sponsoring an sponsee's account or object it no longer wants to support, because it can submit a SponsorshipTransfer transaction at any point.

The sponsor's signature must always include the Account and Sequence fields, to prevent signature replay attacks (where the sponsor's signature can be reused to sponsor an object or account that they did not want to sponsor).

When sponsoring transaction fees, the sponsor must approve of the Fee value of the transaction, since that is the amount that they will be paying.

When sponsoring reserves, the sponsor's signature must include any aspects of the transaction that involve a potential account/object reserve. This would include the Destination field of a Payment transaction (and whether it is a new account) and the TicketSequence field of a TicketCreate transaction (since that dictates how many Ticket objects are created, each of which results in one object reserve).

A sponsee cannot take advantage of the generosity of their sponsor, since the sponsor must sign every transaction it wants to sponsor the ledger objects for. A sponsee also must not be able to change the sponsorship type that the sponsor is willing to engage in, as this could lock up to 500 of the sponsor's XRP (in the case of 250 tickets being created in one TicketCreate transaction).

An axiom that is out of scope: the sponsee may not have any control over a sponsorship transfer (the sponsor may transfer a sponsorship without the sponsee's consent). This is akin to a loanee having no control over a bank selling their mortgage to some other company, or a lender selling debt to a debt collection agency.

17.2. Signatures¶

Since a fee sponsorship must approve of the Fee field, and a reserve sponsorship must approve of a broad set of transaction fields, the sponsor must always sign the whole transaction. This also avoids needing to have different sponsorship processes for different sponsorship types. The same is true for the sponsee's transaction signature; the sponsee must approve of the sponsor and sponsorship type.

A sponsor's Signature cannot be replayed or attached to a different transaction, since the whole transaction (including the Account and Sequence values) must be signed.

18. Invariants¶

An invariant is a statement, usually an equation, that must always be true for every valid ledger state on the XRPL. Invariant checks serve as a last line of defense against bugs; the tecINVARIANT_FAILED error is thrown if an invariant is violated (which ideally should never happen).

18.1. Tracking Owner Counts¶

A transaction that creates a ledger object either increments an account's OwnerCount by 1 or increments two separate accounts' SponsoringOwnerCount and SponsoredOwnerCount by 1. The opposite happens when a ledger object is deleted.

The equivalent also should happen with SponsoringAccountCount.

18.2. Balancing SponsoredOwnerCount and SponsoringOwnerCount¶

$$ \sum{accounts} Account.SponsoredOwnerCount = \sum Account.SponsoringOwnerCount $$

In other words, the sum of all accounts' SponsoredOwnerCounts must be equal to the sum of all accounts' SponsoringOwnerCounts. This ensures that every sponsored object is logged as being sponsored and also has a sponsor.

19. Example Flows¶

19.1. Fee Sponsorship¶

19.1.1. The Unsigned Transaction¶

{
  TransactionType: "Payment",
  Account: "rOldB3E44wS6SM7KL3T3b6nHX3Jjua62wg",
  Destination: "rNewfcu9RJa5W1ncAuEgLH1Xpi4j1vzXjr",
  Amount: "20000000",
  Sequence: 3,
  Fee: "10",
  Sponsor: "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
  SponsorFlags: 1
}

19.1.2. The Signed Transaction¶

{
  TransactionType: "Payment",
  Account: "rSender7NwD9vmNf5dvTbW4FQDNSRsfPv6",
  Destination: "rDestinationT6N5fJdaHnRqLpW1D8oFrZ",
  Amount: "20000000",
  Sequence: 3,
  Fee: "10",
  Sponsor: "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
  SponsorFlags: 1,
  SponsorSignature: {
    SigningPubKey: "03072BBE5F93D4906FC31A690A2C269F2B9A56D60DA9C2C6C0D88FB51B644C6F94", // rSponsor's public key
    Signature: "3045022100C15AFB7C0C4F5EDFEC4667B292DAB165B96DAF3FFA6C7BBB3361E9EE19E04BC70220106C04B90185B67DB2C67864EB0A11AE6FB62280588954C6E4D9C1EF3710904D"
  },
  SigningPubKey: "03A8D0093B0CD730F25E978BF414CA93084B3A2CBB290D5E0E312021ED2D2C1C8B", // rAccount's public key
  TxnSignature: "3045022100F2AAF90D8F9BB6C94C0C95BA31E320FC601C7BAFFF536CC07076A2833CB4C7FF02203F3C76EB34ABAD61A71CEBD42307169CDA65D9B3CA0EEE871210BEAB824E524B"
}

19.2. Account Sponsorship¶

The only way an account can be created is via a Payment transaction. So the sponsor relationship must be initiated on the Payment transaction.

19.2.1. The Unsigned Transaction¶

{
  TransactionType: "Payment",
  Account: "rOldB3E44wS6SM7KL3T3b6nHX3Jjua62wg",
  Destination: "rNewfcu9RJa5W1ncAuEgLH1Xpi4j1vzXjr",
  Amount: "20000000",
  Sequence: 3,
  Fee: "10",
  Sponsor: "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
  SponsorFlags: 2,
}

19.2.2. The Signed Transaction¶

{
  TransactionType: "Payment",
  Account: "rOldB3E44wS6SM7KL3T3b6nHX3Jjua62wg",
  Destination: "rNewfcu9RJa5W1ncAuEgLH1Xpi4j1vzXjr",
  Amount: "20000000",
  Sequence: 3,
  Fee: "10",
  Sponsor: "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
  SponsorFlags: 2,
  SponsorSignature: {
    SigningPubKey: "03072BBE5F93D4906FC31A690A2C269F2B9A56D60DA9C2C6C0D88FB51B644C6F94", // rSponsor's public key
    Signature: "30440220702ABC11419AD4940969CC32EB4D1BFDBFCA651F064F30D6E1646D74FBFC493902204E5B451B447B0F69904127F04FE71634BD825A8970B9467871DA89EEC4B021F8"
  },
  SigningPubKey: "03BC74CA0B765281E31E342017D97B3F6743A05FBA23D2114B98FC8AD26D92856C", // rAccount's public key
  TxnSignature: "30440220245217F931FDA0C5E68B935ABB4920211D5B6182878583124DE4663B19F00BEC022070BE036264760551CF40E9DAFC8B84036FA70E7EE7257BB7E39AEB7354B2EB86"
}

19.3. Object Sponsorship¶

19.3.1. The Unsigned Transaction¶

{
  TransactionType: "TicketCreate",
  Account: "rAccount4yjv1j2x79wXxRVXnFbwsjUWXo",
  TicketCount: 100,
  Sequence: 3,
  Fee: "10",
  Sponsor: "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
  SponsorFlags: 2,
}

19.3.2. The Signed Transaction¶

{
  TransactionType: "TicketCreate",
  Account: "rAccount4yjv1j2x79wXxRVXnFbwsjUWXo",
  TicketCount: 100,
  Sequence: 3,
  Fee: "10",
  Sponsor: "rSponsor1VktvzBz8JF2oJC6qaww6RZ7Lw",
  SponsorFlags: 2,
  SponsorSignature: {
    SigningPubKey: "03072BBE5F93D4906FC31A690A2C269F2B9A56D60DA9C2C6C0D88FB51B644C6F94", // rSponsor's public key
    Signature: "30450221009878F3A321250341886FE344E0B50700C8020ABAA25301925BD84DDB5421D432022002A3C72C54BACB5E7DAEC48E2A1D75DCBB8BA3B2212C7FC22F070CCABAF76EC1"
  },
  SigningPubKey: "03BC74CA0B765281E31E342017D97B3F6743A05FBA23D2114B98FC8AD26D92856C", // rAccount's public key
  TxnSignature: "3044022047CB72DA297B067C0E69045B7828AD660F8198A6FA03982E31CB6D27F0946DDE022055844EB63E3BFF7D9ABFB26645AA4D2502E143F4ABEE2DE57EB87A1E5426E010"
}

20. Rationale¶

This section explains the key technical design decisions, why particular choices were made, and how this design compares to similar features on other chains.

20.1. Related Work¶

Sponsored transactions and reserves are a common feature across blockchain ecosystems:

• Stellar implements sponsored reserves using a "sandwich transaction" pattern with BeginSponsoringFutureReserves and EndSponsoringFutureReserves operations wrapped around the sponsored operations.
• Ethereum supports meta-transactions through various standards (EIP-2771, EIP-3009) and account abstraction (ERC-4337), where a relayer submits transactions on behalf of users and pays the gas fees.
• Solana allows fee payers to be specified separately from the transaction signer.

This proposal draws inspiration from these implementations while adapting the concepts to fit the XRPL's account-based model and existing transaction structure.

20.2. Pre-Funded vs. Co-Signed Sponsorship¶

The design supports two modes of sponsorship: pre-funded (via the Sponsorship ledger object) and co-signed (via the Sponsor transaction field). This dual approach was chosen to accommodate different use cases:

• Co-signed sponsorship gives sponsors fine-grained control over each transaction, ideal for high-value or sensitive operations.
• Pre-funded sponsorship reduces operational overhead for sponsors who want to enable many transactions without being involved in each one, while still maintaining limits via MaxFee and ReserveCount.

20.3. Other Designs Considered¶

20.3.1. Per-Transaction Sponsorship vs. Account-Level Sponsorship¶

An earlier design involved updating AccountSet to allow users to add a Sponsor to their account (with a signature from the sponsor as well). The sponsor would then sponsor every object from that account while the field was active, and either the sponsor or the account could remove the sponsorship at any time.

This approach was rejected because it made more sense for the relationship to be specific to a specific transaction(s), to prevent abuse—the sponsor should decide what objects they want to support and what objects they don't want to support. This philosophy (that the sponsorship relationship should be ephemeral to prevent abuse) aligns with Stellar's design.

The current design also supports having different sponsors for different objects, which allows users to use a broad set of services and platforms, instead of being locked into one.

20.3.2. Inner Object vs. Wrapper Transaction¶

An alternative design considered was a wrapper transaction (tentatively named Relay), similar to Batch in XLS-56, that the sponsor would sign. It would contain a sub-transaction from the sponsee.

It would look something like this:

This was inspired by Stellar's sandwich transaction design, but the current inner object design felt cleaner. From an implementation perspective, it's easier to have the fee payer as a part of the existing transaction rather than as a part of a wrapper transaction, since that info needs to somehow get passed down the stack. Also, while the wrapper transaction paradigm will be used in XLS-56, they should be used sparingly in designs—only when necessary—as their flow is rather complicated in the rippled code.

In addition, the signing process becomes complicated (as discovered in the process of developing XLS-56). You have to somehow prevent the sponsor from submitting the as-is signed transaction to the network, without including it in the wrapper transaction.

20.3.2. Create-Accept-Cancel Flow¶

Another design considered was to have a new set of transactions (e.g. SponsorCreate/SponsorAccept/SponsorCancel/SponsorFinish) where a sponsor could take on the reserve for an existing object.

This design was never seriously considered, as it felt too complicated and introduced several new transactions. It also doesn't support adding a sponsor to the object at object creation time, which is a much smoother UX and never requires the owner/sponsee to hold enough XRP for the reserve.

21. Backwards Compatibility¶

This amendment introduces new functionality while maintaining compatibility with existing ledger states and transactions.

21.1. Pre-Amendment Ledgers and Transactions¶

All ledgers and transactions created before the Sponsor amendment are activated remain valid. The amendment does not modify or invalidate any existing ledger entries or historical transactions.

21.2. Changes to AccountDelete Behavior¶

The AccountDelete transaction has two new behavioral changes:

1. Destination Constraint for Sponsored Accounts: If an account being deleted has a Sponsor field (indicating the account reserve is sponsored), the Destination field of the AccountDelete transaction must equal the Sponsor. This ensures sponsors can recoup their reserve. Accounts without sponsorship can still use AccountDelete with any valid destination as before.

2. New Failure Condition: AccountDelete will fail with tecHAS_OBLIGATIONS if the account has non-zero SponsoringOwnerCount or SponsoringAccountCount fields, indicating the account is currently sponsoring other accounts or objects. This prevents sponsors from deleting their accounts while they have active sponsorship obligations.

21.3. Reserve Accounting Changes¶

The amendment introduces new fields that affect reserve calculations:

• New AccountRoot Fields: Sponsor, SponsoredOwnerCount, SponsoringOwnerCount, and SponsoringAccountCount modify how an account's required XRP reserve is calculated.
• New Ledger Entry Fields: The Sponsor field (and HighSponsor/LowSponsor for RippleState) indicates when an object's reserve is sponsored.
• Reserve Calculation: The reserve formula changes from acctReserve + objReserve * OwnerCount to account for sponsored objects and sponsorship obligations (see section 6.2).

Accounts without these new fields continue to use the existing reserve calculation, ensuring backward compatibility.

21.4. Impact on Tooling and Applications¶

Legacy tooling that does not understand the new sponsorship fields may experience the following:

• Display Issues: Tools may not correctly display or interpret Sponsor, SponsoredOwnerCount, SponsoringOwnerCount, and SponsoringAccountCount fields.
• Reserve Calculations: Tools that calculate required reserves may produce incorrect results if they do not account for the new reserve formula.
• RPC Methods: The new account_sponsoring RPC method and the sponsored filter on account_objects will not be available in tools that have not been updated.
• Transaction Construction: Tools will need updates to support constructing transactions with the Sponsor field and handling the dual-signature flow.

Applications should be updated to recognize and handle these new fields to provide accurate information to users.

21.5. Amendment Activation¶

The Sponsor amendment must be enabled via the standard amendment process. Once activated:

• New transactions can include the Sponsor field to enable fee and reserve sponsorship.
• New ledger entries can include sponsorship-related fields.
• The new Sponsorship ledger entry type becomes available.
• The new SponsorshipSet and SponsorshipTransfer transaction types become available.
• The Payment transaction accepts the new tfSponsorCreatedAccount flag.

Before activation, transactions attempting to use these features will be rejected.

22. Test Plan¶

This section outlines the testing strategy for the sponsored fees and reserves feature. A comprehensive test plan is essential to ensure the correctness and security of this amendment.

22.1. Unit Tests for Ledger Entries¶

Sponsorship Object Tests:

• Creation of Sponsorship objects via SponsorshipSet with various field combinations
• Updates to existing Sponsorship objects (modifying FeeAmount, MaxFee, ReserveCount)
• Deletion of Sponsorship objects via SponsorshipSet with tfDeleteObject flag
• Validation of invariants: Owner != Sponsee, FeeAmount >= 0 and denominated in XRP, ReserveCount >= 0
• Proper handling of lsfSponsorshipRequireSignForFee and lsfSponsorshipRequireSignForReserve flags
• Verification that Sponsorship objects are deletion blockers

AccountRoot Field Tests:

• Addition and removal of Sponsor field on accounts
• Correct tracking of SponsoredOwnerCount, SponsoringOwnerCount, and SponsoringAccountCount
• Reserve calculation with new fields (see section 6.2)
• Interaction between sponsored and unsponsored objects on the same account

RippleState Field Tests:

• Addition and removal of HighSponsor and LowSponsor fields
• Verification that Sponsor common field is not used on RippleState objects
• Proper handling of bidirectional trust line sponsorship

22.2. Unit Tests for Transactions¶

SponsorshipSet Transaction Tests:

• Creating new Sponsorship objects with valid and invalid parameters
• Updating existing Sponsorship objects
• Deleting Sponsorship objects and verifying fund return to sponsor
• Failure conditions: invalid account combinations, invalid fee/reserve values, conflicting flags
• Proper increment/decrement of owner counts and sponsorship counters

SponsorshipTransfer Transaction Tests:

• Transferring sponsorship of objects to new sponsors
• Dissolving sponsorship (returning reserve burden to owner)
• Transferring sponsorship of accounts
• Failure conditions: insufficient reserves, invalid accounts, unauthorized submitters
• Proper updates to SponsoringOwnerCount, SponsoringAccountCount, and SponsoredOwnerCount

Payment Transaction Tests:

• Creating sponsored accounts using tfSponsorCreatedAccount flag
• Fee sponsorship via Sponsor field with tfSponsorFee flag
• Reserve sponsorship for new accounts via Sponsor field with tfSponsorReserve flag
• Combined fee and reserve sponsorship
• Failure conditions: invalid sponsor signatures, insufficient sponsor funds

AccountDelete Transaction Tests:

• Deleting sponsored accounts with correct destination (must be sponsor)
• Failure when destination is not the sponsor for sponsored accounts
• Failure with tecHAS_OBLIGATIONS when account has non-zero SponsoringOwnerCount or SponsoringAccountCount
• Proper decrement of sponsor's counters upon successful deletion

Common Transaction Field Tests:

• Valid and invalid Sponsor field structures
• Single-signature sponsorship (SigningPubKey + TxnSignature)
• Multi-signature sponsorship (Signers array)
• Validation of tfSponsorFee and tfSponsorReserve flags
• Fee calculation with sponsor signatures (multi-sig overhead)
• Pre-funded sponsorship (using Sponsorship object) vs. co-signed sponsorship
• Signature validation and replay attack prevention

22.3. Invariant Tests¶

Owner Count Balancing:

• Verify that object creation increments either OwnerCount or both SponsoringOwnerCount and SponsoredOwnerCount
• Verify that object deletion decrements the appropriate counters
• Test the global invariant: Σ SponsoredOwnerCount = Σ SponsoringOwnerCount

Account Count Balancing:

• Verify that sponsored account creation increments SponsoringAccountCount on sponsor
• Verify that sponsored account deletion decrements SponsoringAccountCount on sponsor

Reserve Consistency:

• Verify that accounts always have sufficient XRP to meet their reserve requirements
• Test edge cases where sponsorship changes affect reserve calculations

22.4. Integration Tests¶

End-to-End Co-Signed Sponsorship Flow:

• Sponsee constructs and autofills transaction
• Sponsor signs transaction
• Sponsee adds sponsor signature and signs transaction
• Transaction is submitted and validated
• Verify correct state changes and fee/reserve handling

End-to-End Pre-Funded Sponsorship Flow:

• Sponsor creates Sponsorship object with SponsorshipSet
• Sponsee constructs transaction with Sponsor field
• Transaction is submitted without sponsor signature (using pre-funded amounts)
• Verify FeeAmount and ReserveCount are decremented correctly
• Test exhaustion of pre-funded amounts

Error Case Testing:

• Insufficient sponsor funds for fees
• Insufficient sponsor reserves for objects
• Exceeding MaxFee limit in Sponsorship object
• Exceeding ReserveCount limit in Sponsorship object
• Invalid or missing sponsor signatures
• Signature replay attempts

Sponsorship Transfer Flows:

• Sponsor transfers object sponsorship to new sponsor
• Sponsor dissolves sponsorship, returning burden to owner
• Owner transfers sponsorship to new sponsor
• Test with insufficient reserves on receiving party

22.5. RPC Tests¶

account_objects with sponsored Filter:

• Retrieve only sponsored objects (sponsored: true)
• Retrieve only unsponsored objects (sponsored: false)
• Retrieve all objects (omit sponsored parameter)
• Test pagination with sponsored filter
• Test interaction with type filter

account_sponsoring RPC Method:

• Retrieve all objects sponsored by an account
• Test pagination with limit and marker
• Test deletion_blockers_only filter
• Test with various type filters
• Verify correct response format and field presence
• Test error conditions: invalid account, missing ledger

22.6. Performance and Stress Tests¶

• Create maximum number of sponsored objects per account
• Test with large Sponsorship object counts
• Verify performance of reserve calculations with many sponsored objects
• Test transaction throughput with sponsored transactions

22.7. Amendment Activation Tests¶

• Verify that sponsorship features are unavailable before amendment activation
• Verify that sponsorship features become available after amendment activation
• Test that pre-amendment ledgers and transactions remain valid post-activation

23. Reference Implementation¶

https://github.com/XRPLF/rippled/pull/5887

24. n+1. Remaining TODOs/Open Questions¶

• Should fee sponsorship allow for the existing fee paradigm that allows users to dip below the reserve?
• Should a sponsored account be prevented from sponsoring other accounts? By default the answer is no, so unless there's a reason to do so, we should leave it as is.

Appendix¶

Appendix A: FAQ¶

A.1: Does the sponsee receive any XRP for the reserve?¶

No, there is no XRP transfer in a sponsorship relationship - the XRP stays in the sponsor's account. The burden of the reserve for that object/account is just transferred to the sponsor.

A.2: What happens if you try to delete your account and you have sponsored objects?¶

If the account itself is sponsored, then it can be deleted, but the destination of the AccountDelete transaction (in other words, where the leftover XRP goes) must be the sponsor's account. This ensures that the sponsor gets their reserve back, and the sponsee cannot run away with those funds.

If the sponsee still has sponsored objects, those objects will follow the same rules of deletion blockers. Whether or not they are sponsored is irrelevant.

If a sponsored object is deleted (either due to normal object deletion processes or, in the case of objects that aren't deletion blockers, because the owner account is deleted), the sponsor's reserve becomes available again.

A.3: What if a sponsor that is sponsoring a few objects wants to delete their account?¶

An account cannot be deleted if it is sponsoring any existing accounts or objects. They will need to either delete those objects (by asking the owner to do so, as they cannot do so directly) or use the SponsorshipTransfer transaction to relinquish control of them.

A.4: Does a sponsor have any powers over an object they pay the reserve for? I.e. can they delete the object?¶

No. If a sponsor no longer wants to support an object, they can always use the SponsorshipTransfer transaction instead to transfer the reserve burden back to the sponsee.

A.5: What if a sponsee refuses to delete their account when a sponsor wants to stop supporting their account?¶

The sponsor will have the standard problem of trying to get ahold of a debtor to make them pay. They may use the SponsorshipTransfer transaction to put the onus on the sponsee. If the sponsee does not have enough XRP to cover the reserve for those objects, they will not be able to create any more objects until they do so.

A.6: What happens if the sponsor tries to SponsorshipTransfer but the sponsee doesn't have enough funds to cover the reserve?¶

If the sponsor really needs to get out of the sponsor relationship ASAP without recouping the value of the reserve, they can pay the sponsee the amount of XRP they need to cover the reserve. These steps can be executed atomically via a Batch transaction, to ensure that the sponsee can't do something else with the funds before the SponsorshipTransfer transaction is validated.

A.7: Would sponsored accounts carry a lower reserve?¶

No, they would still carry a reserve of 1 XRP at current levels.

A.8: Can an existing unsponsored ledger object/account be sponsored?¶

Yes, with the SponsorshipTransfer transaction.

A.9: Can a sponsored account be a sponsor for other accounts/objects?¶

Yes, though they will have to use their own XRP for this (not from another sponsor).

A.10: Can a sponsored account hold unsponsored objects, or objects sponsored by a different sponsor?¶

Yes, and yes.

A.11: What if I want different sponsors to sponsor the transaction fee vs. the reserve for the same transaction?¶

That will not be supported by this proposal. If you have a need for this, please provide example use-cases.

A.12: Won't it be difficult to add two signatures to a transaction?¶

This is something that good tooling can solve. It could work similarly to how multisigning is supported in various tools.

A.13. Why not instead do [insert some other design]?¶

See Appendix B for the alternate designs that were considered and why this one was preferred. If you have another one in mind, please describe it in the comments and we can discuss.

A.14: How is this account sponsorship model different from/better than XLS-23, Lite Accounts?¶

• Sponsored accounts do not have any restrictions, and can hold objects.
• Sponsored accounts require the same reserve as a normal account (this was one of the objections to the Lite Account proposal).
• Lite accounts can be deleted by their sponsor.

A.15: How will this work for objects like trustlines, where multiple accounts might be holding reserves for it?¶

The answer to this question is still being explored. One possible solution is to add a second field, Sponsor2, to handle the other reserve.

A.16: How does this proposal work in conjunction with XLS-49? What signer list(s) have the power to sponsor fees or reserves?¶

Currently, only the global signer list is supported. Another SignerListID value could be added to support sponsorship. Transaction values can only go up to $2^{16}$, since the TransactionType field is a UInt16, but the SignerListID field goes up to $2^{32}$, so there is room in the design for additional values that do not correlate to a specific transaction type.