Auth Code (Card Authorization Code)

An auth code (authorization code) is a 6-digit alphanumeric value the card network (Visa, Mastercard, Amex, Discover) returns when it approves a transaction. It’s the merchant’s proof that the bank authorized the charge — critical for defending against chargebacks.

Receipts that involve a card payment will print the auth code, typically labeled "AUTH:", "AUTH CODE:", or "APPROVAL:". Some POS systems also print "REF:" (reference) and "BATCH:" (batch number) for reconciliation.

Card processors generate auth codes randomly with no semantic meaning — they’re just unique identifiers. A typical auth code looks like "823491" or "Z47Q12".

On gas pump receipts, the auth code often serves as the de facto transaction ID since pumps don’t generate their own TC# the way a retail POS does.