Reference pagesReason codes
Processing error
American Express P08: Duplicate Transaction
An 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 the app handles it
How long you have to respond
- Merchant response
- 20 days from the inquiry or chargeback notice
Where this comes from
- American Express, Merchant Regulations International, 17 April 2026
- Stripe, reason code categories Accessed 8 September 2026.
Other American Express processing error codes
Do The Proof drafts dispute responses for Shopify stores.
You pay when a dispute is won. Not before.