Amex's not-as-described code, decided on the merchant's product representation at checkout and the cardmember's communication before the chargeback.
Amex C31 is filed when the cardmember received the goods or service but says it did not match the merchant's description, the listing, or the agreed quality. The dispute is decided on what the merchant represented at the point of sale and how the merchant responded when the cardmember raised the issue. It is the Amex parallel to Visa 13.3 and the not-as-described condition of Mastercard 4853.
How the dispute actually arrives
The merchant has 20 days from receipt of the C31 notification to respond. C31 is among the harder Amex codes to defend in 2026 because the issuer reads the dispute as a buyer-protection claim: if the cardmember says the product was not as described and the merchant did not offer a reasonable remedy first, the issuer tends to side with the buyer.
What the issuer is looking for
Amex wants the product representation at checkout, and the merchant's response when the cardmember complained. If the listing accurately described what was delivered, the dispute often turns on the buyer's communication. A cardmember who used the product for three months, never contacted the merchant, and then filed C31 has a weak case if the listing was accurate. A cardmember who emailed within a week, was ignored, and then filed C31 has a strong one.
The merchant's remediation offer matters as much as the original representation. Amex's underlying assumption is that an honest merchant offers a refund or replacement when a real not-as-described issue is raised. Refusal to remediate, or radio silence, tilts the issuer toward the cardmember regardless of the evidence on the product itself.
Common scenarios merchants see
A physical-goods order where the buyer says colour, size, material, or quality differs from the listing. Listing screenshots from the time of sale, paired with photos of what was shipped, are the centrepiece of the case.
A digital product or course where the cardmember says the content did not match the marketing page. The marketing page at the time of sale is the framing document. If the merchant has changed the page since, an archived version is the missing piece most merchants do not have.
A service whose scope the cardmember disputes. The booking confirmation, statement of work, or signed agreement defines the scope. Without one, the case is largely the cardmember's word against the merchant's.
A subscription whose features changed mid-term. Cardmember consent to material feature changes, through email notice or in-app acceptance, is what the issuer will look for.
What this code is not
C31 is not a non-receipt code, a fraud claim, or a refund-failure code. The cardmember acknowledges receipt; they are complaining about what was received. Treating C31 as a delivery dispute by leading with tracking proof is the most common loss pattern.
Where this fits in our service
Amex C31 letters are built from the listing, the delivery evidence, and the communication trail with the cardmember. We draft them when the listing was accurate and the merchant offered reasonable remediation; we tell the merchant honestly when the listing or the response is the weak link. If you have just received one, you can start with a free first letter.
Official source: Amex rules. Last reviewed 2026-05-14.