Acquirer Reference Number

An acquirer reference number, commonly shortened to ARN, is a unique identifier that the merchant's acquirer attaches to a card transaction when it submits the transaction for clearing through the card network. It follows the transaction from the acquirer to the network and on to the card issuer, so all three parties can find the same record later.

On the major international networks the ARN is a 23-digit number. It is mainly used behind the scenes, but it often appears in conversations about refunds: when a cardholder cannot see a refund on their statement, the merchant or its payment provider may give them the ARN so that the issuer can locate it. It is different from identifiers created at the authorisation stage, such as the retrieval reference number and the authorisation code.

The ARN is built by the acquirer or its processor according to card scheme rules. While details vary, the number typically combines:

• A format or indicator digit at the start.
• The acquirer's identifier, closely linked to its acquirer identification number or BIN, which tells the network which acquirer sent the item.
• A processing date, often written in a year and day-of-year format.
• A sequence or batch number, which makes the reference unique among that acquirer's items for the day.
• A check digit at the end, used to catch typing errors.

Because the number is assigned at clearing, it exists only once the merchant has captured and submitted the sale or refund, usually a day or more after the purchase. Authorised but uncaptured transactions, and authorisations that were later reversed, do not have one.

The ARN is carried in the clearing message and stored by every party, which makes it the main key for any later action on the transaction. Common uses include:

• Tracing refunds. A refund is a separate credit transaction with its own ARN. If a cardholder says a refund has not arrived, the issuer can search for that ARN to show whether and when it was received, which avoids an unnecessary dispute.
• Chargebacks. When an issuer raises a chargeback, it quotes the ARN of the original sale, and the acquirer uses it to identify the merchant and transaction. Later stages, such as representment and arbitration, keep referring to the same ARN.
• Retrieval requests. If an issuer asks for a copy of the sales receipt, the request is matched to the transaction by ARN.
• Reconciliation. Acquirers and large merchants match ARNs in their settlement reports against their sales records as part of transaction reconciliation.

A card transaction gathers several references as it moves through its life. The merchant may have its own order number, the terminal or gateway creates a transaction ID, the authorisation produces an approval code and a retrieval reference number, and the network may add its own transaction identifier to link authorisation and clearing. The ARN is the reference that the issuer and acquirer both hold for the cleared item, which is why it is the most useful number for tracing money after the purchase. Payment providers often display it in their dashboards next to the general transaction identifier.

Refunds are where most merchants and consumers meet the ARN. After a merchant issues a refund, it goes through the same clearing process as a sale, and the issuer usually posts the credit within several business days, though timing depends on the issuer. If the cardholder has not seen the money, the merchant can share the refund ARN as proof that it was sent. The cardholder then gives the number to their bank, whose staff can search the network records. If the issuer confirms receipt, the matter is usually settled without a dispute; if a chargeback has already been raised, the acquirer can use the refund ARN as evidence that the cardholder was already credited, which supports a representment. Many payment service providers now show refund ARNs in their merchant dashboards and send them automatically to customers on request, reducing support calls and avoidable disputes. Issuers, for their part, may use the ARN to find refunds that were applied to an old or replaced card number.

Cardholders rarely see the ARN, and customer service staff at banks are not always trained to use it, so refund queries can still take time. The ARN also does not show where money is after clearing; it proves that the acquirer submitted the item, not that the issuer has posted it to the cardholder's account. For non-card payments, other references serve similar purposes, such as the trace number in ACH or the unique end-to-end transaction reference in SWIFT payments. For general questions about card disputes, see payment dispute.