Payment

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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.)

Payments are also the only way to create accounts.

Example Payment JSON

{
  "TransactionType" : "Payment",
  "Account" : "rf1BiGeXwwQoi8Z2ueFYTEXSwuJYfV2Jpn",
  "Destination" : "ra5nK24KXen9AHvsdFTKHSANinZseWnPcX",
  "Amount" : {
     "currency" : "USD",
     "value" : "1",
     "issuer" : "rf1BiGeXwwQoi8Z2ueFYTEXSwuJYfV2Jpn"
  },
  "Fee": "12",
  "Flags": 2147483648,
  "Sequence": 2,
}

Payment Fields

In addition to the common fields, a Payment transaction uses the following fields:

Field JSON Type Internal Type Description
Amount Currency Amount Amount The amount of currency to deliver. For non-XRP amounts, the nested field names MUST be lower-case. If the tfPartialPayment flag is set, deliver up to this amount instead.
Destination String Account The unique address of the account receiving the payment.
DestinationTag Unsigned Integer UInt32 (Optional) Arbitrary tag that identifies the reason for the payment to the destination, or a hosted recipient to pay.
InvoiceID String Hash256 (Optional) Arbitrary 256-bit hash representing a specific reason or identifier for this payment.
Paths Array of path arrays PathSet (Optional, auto-fillable) Array of payment paths to be used for this transaction. Must be omitted for XRP-to-XRP transactions.
SendMax Currency Amount Amount (Optional) Highest amount of source currency this transaction is allowed to cost, including transfer fees, exchange rates, and slippage. Does not include the XRP destroyed as a cost for submitting the transaction. For non-XRP amounts, the nested field names MUST be lower-case. Must be supplied for cross-currency/cross-issue payments. Must be omitted for XRP-to-XRP payments.
DeliverMin Currency Amount Amount (Optional) Minimum amount of destination currency this transaction should deliver. Only valid if this is a partial payment. For non-XRP amounts, the nested field names are lower-case.

Special issuer Values for SendMax and Amount

Most of the time, the issuer field of a non-XRP Currency Amount indicates a financial institution's issuing address. However, when describing payments, there are special rules for the issuer field in the Amount and SendMax fields of a payment.

  • There is only ever one balance for the same currency between two addresses. This means that, sometimes, the issuer field of an amount actually refers to a counterparty that is redeeming issuances, instead of the address that created the issuances.
  • When the issuer field of the destination Amount field matches the Destination address, it is treated as a special case meaning "any issuer that the destination accepts." This includes all addresses to which the destination has extended trust lines, as well as issuances created by the destination which are held on other trust lines.
  • When the issuer field of the SendMax field matches the source account's address, it is treated as a special case meaning "any issuer that the source can use." This includes creating new issuances on trust lines that other accounts have extended to the source account, and sending issuances the source account holds from other issuers.

Creating Accounts

The Payment transaction type can create new accounts in the XRP Ledger by sending enough XRP to an unfunded address. Other transactions to unfunded addresses always fail.

For more information, see Accounts.

Paths

If present, the Paths field must contain a path set - an array of path arrays. Each individual path represents one way value can flow from the sender to receiver through various intermediary accounts and order books. A single transaction can potentially use multiple paths, for example if the transaction exchanges currency using several different order books to achieve the best rate.

You must omit the Paths field for direct payments, including:

  • An XRP-to-XRP transfer.
  • A direct transfer on a trust line that connects the sender and receiver.

If the Paths field is provided, the server decides at transaction processing time which paths to use, from the provided set plus a default path (the most direct way possible to connect the specified accounts). This decision is deterministic and attempts to minimize costs, but it is not guaranteed to be perfect.

The Paths field must not be an empty array, nor an array whose members are all empty arrays.

For more information, see Paths.

Payment Flags

Transactions of the Payment type support additional values in the Flags field, as follows:

Flag Name Hex Value Decimal Value Description
tfNoDirectRipple 0x00010000 65536 Do not use the default path; only use paths included in the Paths field. This is intended to force the transaction to take arbitrage opportunities. Most clients do not need this.
tfPartialPayment 0x00020000 131072 If the specified Amount cannot be sent without spending more than SendMax, reduce the received amount instead of failing outright. See Partial Payments for more details.
tfLimitQuality 0x00040000 262144 Only take paths where all the conversions have an input:output ratio that is equal or better than the ratio of Amount:SendMax. See Limit Quality for details.

Partial Payments

A partial payment allows a payment to succeed by reducing the amount received. Partial payments are useful for returning payments without incurring additional costs to oneself. However, partial payments can also be used to exploit integrations that naively assume the Amount field of a successful transaction always describes the exact amount delivered.

A partial payment is any Payment transaction with the tfPartialPayment flag enabled. A partial payment can be successful if it delivers any positive amount greater than or equal to its DeliverMin field (or any positive amount at all if DeliverMin is not specified) without sending more than the SendMax value.

The delivered_amount field of a payment's metadata indicates the amount of currency actually received by the destination account.

For more information, see the full article on Partial Payments.

Limit Quality

The XRP Ledger defines the "quality" of a currency exchange as the ratio of the numeric amount in to the numeric amount out. For example, if you spend $2 USD to receive £1 GBP, then the "quality" of that exchange is 0.5.

The tfLimitQuality flag allows you to set a minimum quality of conversions that you are willing to take. This limit quality is defined as the destination Amount divided by the SendMax amount (the numeric amounts only, regardless of currency). When set, the payment processing engine avoids using any paths whose quality (conversion rate) is worse (numerically lower) than the limit quality.

By itself, the tfLimitQuality flag reduces the number of situations in which a transaction can succeed. Specifically, it rejects payments where some part of the payment uses an unfavorable conversion, even if the overall average average quality of conversions in the payment is equal or better than the limit quality. If a payment is rejected in this way, the transaction result is tecPATH_DRY.

Consider the following example. If I am trying to send you 100 Chinese Yuan (Amount = 100 CNY) for 20 United States dollars (SendMax = 20 USD) or less, then the limit quality is 5. Imagine one trader is offering ¥95 for $15 (a ratio of about 6.3 CNY per USD), but the next best offer in the market is ¥5 for $2 (a ratio of 2.5 CNY per USD). If I were to take both offers to send you 100 CNY, then it would cost me 17 USD, for an average quality of about 5.9.

Without the tfLimitQuality flag set, this transaction would succeed, because the $17 it costs me is within my specified SendMax. However, with the tfLimitQuality flag enabled, the transaction would fail instead, because the path to take the second offer has a quality of 2.5, which is worse than the limit quality of 5.

The tfLimitQuality flag is most useful when combined with partial payments. When both tfPartialPayment and tfLimitQuality are set on a transaction, then the transaction delivers as much of the destination Amount as it can, without using any conversions that are worse than the limit quality.

In the above example with a ¥95/$15 offer and a ¥5/$2 offer, the situation is different if my transaction has both tfPartialPayment and tfLimitQuality enabled. If we keep my SendMax of 20 USD and a destination Amount of 100 CNY, then the limit quality is still 5. However, because I am doing a partial payment, the transaction sends as much as it can instead of failing if the full destination amount cannot be sent. This means that my transaction consumes the ¥95/$15 offer, whose quality is about 6.3, but it rejects the ¥5/$2 offer because that offer's quality of 2.5 is worse than the quality limit of 5. In the end, my transaction only delivers ¥95 instead of the full ¥100, but it avoids wasting money on poor exchange rates.