MCC Lookup

Who chooses the code

The acquirer does, when it boards the merchant. Not the cardholder, not the terminal, and not the scheme. So the code is a claim about what a business sells rather than a fact about what was just bought, and a supermarket with a petrol station and a pharmacy inside it still sends one MCC per merchant outlet.

That matters because a lot rides on this four-digit number: your interchange rate, whether surcharging is permitted in your country, which rewards category the cardholder earns, and whether the issuer's rules block the transaction outright. Miscoding is a real and occasionally intentional problem, and it is the kind that surfaces months later as an interchange adjustment.

Cash-like codes behave differently for the cardholder

Two categories get priced as cash, and this table names which is which rather than calling everything quasi-cash.

Cash disbursement, meaning 6010 over the counter and 6011 at an ATM, is actual money. Quasi-cash covers 4829, 6051, 6540, 7995 and 9223: the purchase of something cash-like, such as currency, cryptocurrency, a prepaid load, a gambling stake or a bail bond.

They are not the same category, but issuers price them alike: a cash-advance fee, interest from day one with no grace period, and often a separate and much lower limit than the card's purchase limit. A cardholder who is declined on a quasi-cash transaction while their purchase limit is plainly untouched has usually hit that second limit rather than a fraud rule.

6051 is the one to know. It is the code cryptocurrency purchases usually carry, and a good number of issuers block it outright as policy rather than as a risk decision.

An unlisted code still tells you something

ISO 18245 divides the space into fixed blocks, so even a code nobody has published a description for is locatable: 3000-3299 is always an airline, 3300-3499 car rental, 3500-3999 lodging, 8000-8999 a professional service. Those three blocks in the 3000s are almost entirely individual brands, one code per airline, per rental company and per hotel chain, and no free source lists them completely.

So an unrecognised code here resolves to its block and says so, rather than offering the nearest business that looks about right. "In the airlines block" is a fact. "Probably British Airways" is a guess, and a guess is what you would then go and act on.

Fuel is its own problem

5541 and 5542, attended and unattended fuel, authorise for an estimated amount and complete for the real one. That is why a cardholder sees a hold that does not match the receipt, and why fuel disputes are disproportionately about amounts that were never taken. If you are reconciling fuel transactions, match on the completion, not the authorisation.

Where it appears

DE 18 in an ISO 8583 message, and tag 9F15 in EMV chip data, where the terminal holds it for the card's own risk checks. The two should agree; if they do not, the terminal was configured separately from the merchant record, which is worth chasing down. Paste a whole message into the message decoder and DE 18 comes out resolved against this table.