An online or phone merchant sends the same evidence on two disputes in one week where the customer says the order never arrived: a Visa 13.1 and an Amex C08. Visa decides for the merchant and Amex decides for the customer. The merchant assumes the Amex response was written badly, but it probably was not. Industry-observed Amex win rates run 10 to 15 points below Visa on the same evidence, and the gap comes from how Amex is built.
Amex is both the card brand and the bank that issues the card. On Visa or Mastercard the card brand and the customer's bank are separate companies, so a dispute passes through two independent reviews. At Amex one company decides the case and also owns the customer relationship. Customer fees make up roughly half of Amex's revenue, and its customers are more affluent and more willing to dispute. Amex's brand promises them buyer protection, so the merchant is not the reviewer's main customer.
Amex gives the least time of any major card brand to respond: 20 days from notification, against 30 for Visa and 45 for Mastercard, and your payment company's cut-off comes earlier still. A notification that sits in a finance inbox for a week has already used a third of that time. A Visa response can make several arguments and hope one lands. An Amex response has room for one or two that match how Amex reviews that specific dispute reason (the code on your notice).
A $300 dispute worth fighting on Visa 13.1 is usually not worth fighting on Amex, because the short window and the lower win rate work against the merchant. The disputes that clear that higher bar deserve extra care. representments.com drafts each Amex response for the Amex C-series dispute reason in question and refines it as outcomes come in, so merchants can spend their time on the Amex cases that are still winnable and refund the rest.
Sources
- American Express merchant response window for disputes is 20 days from notification, the tightest of any major network.American Express Merchant Reference Guide, 2026 edition