If your card says American Express or Discover, the codes on your letter look nothing like 13.3 or 4853. Amex uses letter-led codes like C31 and F24; Discover uses two-letter codes like AA and UA02. And with Amex, the dispute process itself works differently — because Amex is both the network and the issuer.
Have a code on your letter? Decode it instantly
Type any Amex, Discover, Visa, or Mastercard reason code and get a plain-English explanation.
Two different alphabets: Amex letters, Discover pairs
The format tells you which network you're dealing with at a glance:
American Express: a category letter plus digits — C31, F24, P08, R03. The letter is the family; the digits are the specific dispute.
Discover: two (sometimes more) letters — AA, AP, RM, UA02 — usually paired with a four-digit number in processor records (e.g. UA02 / 7030). Processors render these inconsistently, so match the written allegation rather than the number.
American Express codes: A, C, F, P, R, FR
Amex groups its codes by letter. The family is the letter; the digits are the specific dispute:
C — Cardmember disputes. The everyday family: C31 (goods/services not as described), C32 (damaged or defective), C08 (not received, or only partially), C02 (credit not processed), C04 (returned or refused), C05 (cancelled), C28 (cancelled recurring billing), C14 (paid by other means), C18 (hotel "no-show" or car-rental deposit cancelled). For C31 and C32, Amex is deciding whether the problem is material — photos and the original listing usually decide it.
F — Fraud.F24 (no cardmember authorization) and F29 (card-not-present fraud) are the consumer-relevant ones; F30/F31 cover EMV counterfeit and lost/stolen scenarios. Amex weighs the charge against your purchase history and looks for anything unusual.
A — Authorization.A01 (charge exceeded the authorized amount), A02 (no valid authorization), A08 (authorization expired). Mostly paperwork your issuer side checks.
R / M / FR — Inquiry and miscellaneous.R03/R13 mean an earlier inquiry got an insufficient or no reply — deadlines in Amex disputes are strict, so treat these as warnings to respond fully and fast.
Why Amex disputes work differently (closed loop)
Visa and Mastercard run open loops: your issuing bank argues with the merchant's bank, with the network as referee — and there's a formal arbitration stage if the banks disagree. American Express runs a closed loop: Amex is the network and the issuer, handles the dispute end to end, and there is no formal arbitration — Amex's decision is generally final.
What that means for you:
Your first filing is your best shot. Without arbitration as a backstop, the documentation you submit at the start carries more weight. Don't file thin and hope to add evidence later — cardholders are generally limited to two filings per charge.
Deadlines are strict. Merchants get around 20 days to respond to an Amex inquiry; cardholder filing windows run up to about 120 days depending on the category. Treat every date on your letter as hard.
Your evidence has to speak for itself. On Visa/Mastercard, your issuer has a financial incentive to win your dispute. On Amex, the same company decides the case — so your evidence file does the arguing.
Check what your code means right now
Paste your Amex or Discover code into the decoder for the plain-English breakdown.
Discover's codes are short pairs of letters in five categories. The ones consumers see most:
AA — Does Not Recognize. You don't recognize the merchant or transaction. Before filing, check your own records — many "unrecognized" charges turn out to be unfamiliar billing descriptors for real purchases.
UA02 — Fraud, card-not-present. Your card details were used fraudulently online or by phone. (UA01 is the in-person equivalent; UA05/UA06 cover counterfeit chip scenarios.)
RG — Non-receipt of goods or services and NM — non-receipt of merchandise. You paid; it never arrived. Tracking and delivery-date evidence is the core of the case.
RM — Quality discrepancy and NR — not as described or defective. The Discover equivalents of "not as described" — photos and the original listing usually decide them.
AP — Cancelled recurring transaction. The subscription you cancelled kept charging. Your dated cancellation confirmation is everything.
DP — Duplicate processing. Charged twice for one purchase.
RN2 — Credit not processed. The promised refund never arrived.
SV — Services not rendered. A service you paid for was never performed.
Error family.AW (altered amount), CD (credit posted as a charge), PM (paid by other means), IN (invalid card number), LP (late presentment), AT/DA/NA (authorization problems), EX (expired card), IC (illegible sales data), NF (no ATM cash dispensed), RN (no cash/load value received) — mostly decided on statements and receipts.
One practical note: because processors render Discover's letter-plus-number pairs inconsistently, always match the written allegation on your letter rather than the number alone. If the letters and the description disagree, ask Discover to clarify in writing.
How to read the code on your bank letter
Find the dispute description — the code sits near it, often in parentheses or bold.
Identify the network by format — decimals (13.3) = Visa, four digits (4853) = Mastercard, letter + digits (C31) = Amex, two letters (UA02) = Discover.
Copy it exactly — letters, numbers, and punctuation — into the decoder. Don't paraphrase: "not as described" could be Visa 13.3, Mastercard 4853, Amex C31, or Discover NR, and each travels through different rules.
Check the dates around it — the code sets the evidence expectations; the letter's dates set your deadline. Confirm both with our deadline calculator if anything is unclear.
Codes evolve — verify against your letter
Both Amex and Discover update their dispute rules periodically, and processor paperwork sometimes shows legacy numeric codes alongside (or instead of) the current letters. Any code list is a snapshot — the authoritative source is always the exact code and wording on your current bank letter. If a code on your letter doesn't appear in the decoder, we won't guess: copy it exactly, confirm the network, and ask your issuer what it means rather than assuming. An omitted code is a minor gap; an invented one could send your dispute down the wrong path.
FAQ
Amex & Discover code questions
C31 means the goods or services were not as described. American Express is deciding whether the difference between what was promised and what arrived is material — photos and the original listing usually decide it.
American Express is both the network and the issuer — a closed loop. There is no separate bank arguing on your behalf, and there is no formal arbitration stage: Amex's decision is generally final. That makes complete documentation at the first filing especially important.
Discover uses two-letter codes — AA (does not recognize), UA02 (card-not-present fraud), RG (goods or services never arrived), RM (quality disputed), AP (cancelled recurring), DP (duplicate) — often paired with a four-digit number in processor records. Match the written allegation rather than the number, since processors render them inconsistently.
AA means you told Discover you do not recognize the merchant or transaction. Before filing, check your own records — many "unrecognized" charges turn out to be unfamiliar billing descriptors for legitimate purchases.
Look for the code near the dispute description, then identify the network by its format: Visa uses decimals (13.3), Mastercard uses four digits (4853), Amex uses a letter plus digits (C31), Discover uses two letters (UA02). Copy it exactly — letters, numbers, and punctuation — and decode it rather than guessing.
