American Express Reason Code P01 — Unassigned Account Number
What the cardholder's bank is claiming: Transaction on an unassigned account number.
What a P01 chargeback means
This is a processing-error dispute: the claim is that something mechanical went wrong — a duplicate charge, a wrong amount, a wrong currency or account. The cardholder may be right; check your records before deciding to fight.
What your response must prove
Prove the transaction was processed exactly once, for the correct amount and currency, to the correct account — or show the second charge was a distinct purchase.
Evidence to gather
- Receipts or invoices for each charge, showing they are distinct transactions
- Batch records proving a single settlement for the disputed amount
- The order agreement showing the amount and currency the customer accepted
- Refund records, if a correction was already issued
- Itemized breakdowns separating similar same-day purchases
- Processor exports showing transaction IDs for each charge
How to respond
- Confirm the claim actually fits the facts — if your records show the cardholder is right, a prompt refund beats a lost dispute plus a fee.
- Assemble the evidence above and write a four-part rebuttal: case summary, merchant position, numbered evidence, conclusion. Our step-by-step guide includes a free template, and Shopify merchants should see the Shopify-specific walkthrough.
- Submit through your processor before the deadline. American Express allows typically 20 days, but your processor's cutoff is usually several days earlier — the date in your dashboard is the real one.
Can you win?
Very winnable when the charges were genuinely distinct — two orders, a split shipment, an agreed amount. If your records confirm an actual error, refund promptly instead of fighting; you'll lose and pay the fee.
American Express P01 is built into Chargeback Shield. Pick the code, enter your case details, and get a structured response draft in minutes — your first draft is free.