Reference pagesReason codes
Processing error
American Express P08: Duplicate Transaction
A American Express dispute reason code, what it asks you to prove, and what Do The Proof puts in the response.
What this code means
Processed more than once
What the network says wins it
AUTH: separate transactions
- Authorization and processing records
How Do The Proof handles it
How long you have to respond
- Merchant response
- 20 days from the inquiry or chargeback notice
There is no pre-arbitration. American Express is both the issuer and the network, and rules after one merchant response; it may then issue a final chargeback.
Merchants in the FR2, FR4 and FR6 programmes get no inquiry at all.
Where this comes from
- American Express, Merchant Regulations International, 17 April 2026 Read 2026-09-08.
- Stripe, reason code categories Read 2026-09-08.
Other American Express processing error codes
Do The Proof drafts dispute responses for Shopify stores. Connect store