Amex Reason Code F24: No Card Member Authorization

What Amex reason code F24 means

F24 is a “I didn’t authorize this” fraud claim. Sources describe it in slightly different ways, but the common thread is a Card Member denying a charge, frequently on a card they had stored with you or an account they held. Typical scenarios:

• Account takeover: someone logged into a real customer account and used the saved Amex card.
• Household use: a family member used a stored card or an open session.
• Unrecognized recurring or one-click charges the Card Member says they never agreed to.
• Friendly fraud from a returning customer who made the purchase and disputes it.

If the transaction was a straightforward online or phone order, you’re more likely to see F29 Card Not Present. The exact use of F24 can vary by market, so read the dispute description Amex or your acquirer provides.

Common causes

• Weak account security: no MFA, reused passwords, long-lived sessions
• One-click upsells or reorders that charge a stored card without a clear confirmation
• Unclear consent to store the card for future charges
• Billing descriptors the Card Member doesn’t connect to your brand

Evidence that wins an F24 dispute

1. Authentication records: login timestamp, IP, device, and any MFA or SafeKey result for the session that placed the order.
2. Stored-card consent: the checkout screen or terms where the Card Member agreed to save the card and allow future charges.
3. Purchase history: earlier undisputed charges on the same card and account, ideally from the same device or IP.
4. Fulfillment: delivery to the Card Member’s known address, or usage logs for digital goods.
5. Communication: order-related emails or support contact from the Card Member’s verified address.
6. Account activity after the charge: continued logins or use, which undercuts “I didn’t authorize this.”

Separating account takeover from friendly fraud

The same F24 can be either. Signs of a genuine takeover are a login from a new device or country, a recent password or email change, a new shipping address, and an order unlike the account’s history. Signs of friendly fraud are the reverse: the usual device, the usual address, a familiar product, and continued normal use after the charge. Lay out those signals in the rebuttal so the reviewer can see which pattern this charge fits.

How to prevent F24 disputes

• Add MFA or step-up verification for logins from new devices and for changes to saved cards.
• Confirm one-click purchases with a clear button and an immediate receipt email.
• Store explicit consent for card-on-file use.
• Flag and review accounts with sudden address or email changes before the next charge.

Should you fight or accept?

Fight when your logs tie the charge to the Card Member’s own authenticated account, device and address, and the account shows normal use before and after.

Accept when there are signs of account takeover, such as a new device, a password reset, or a changed shipping address just before the order. Then lock the account and tell the customer.