How does an acquirer reference number work?
Adyen’s glossary describes the ARN as a unique number assigned as the transaction moves from the acquirer through the scheme to the issuer, which can be used to track a payment or refund. Stripe describes it as a 23-digit number whose internal layout differs by network: for Visa it includes segments for the acquiring bank, a Julian date and a daily sequence number. A refund is a separate transaction, so Stripe notes it gets its own ARN, not the one from the original purchase.
Why does it matter?
It is the quickest answer to a customer asking where a refund is. Stripe’s documentation says customers usually see a card refund about 5 to 10 business days after it is issued. Given the ARN, the issuer’s support team can find the credit and tell the customer when it will post. As an illustrative example: a store issues 400 card refunds a month and 10% of those customers contact support. If agents share the ARN in their first reply, those 40 cases can close without a ticket to the provider.
What are the limits?
Not every transaction has one. Stripe notes there is no ARN when a refund goes through as a reversal shortly after the charge, because the original charge was never processed, and that for card networks without ARNs it tries to provide another reference, such as the retrieval reference number. Stripe also points out that the ARN helps trace a refund but does not speed it up, because issuers apply credits on their own schedule.
Where does Omno use it?
ARNs are created by acquirers and passed on by PSPs, so whether one is available for a payment depends on the provider. Omno’s routing-decision log shows which PSP processed each transaction, which tells support teams where to request the reference.