Reason code

American Express reason code M39 is used when Amex reverses or adjusts a transaction to correct an error from a prior charge. This could include fixing a misprocessed refund, double billing, or any transaction where a correction was necessary but not handled properly by the merchant.

This code is typically not cardholder-initiated—it’s triggered by Amex when their systems or investigations determine that a previous transaction was not settled correctly. If the merchant failed to resolve the issue on their own, Amex may process a chargeback to enforce the correction.

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If you’ve already resolved the issue or believe the correction was inaccurate, submit evidence to clarify the transaction history:

• Provide receipts, refund records, or transaction logs showing the matter was properly addressed

• Include any customer communications confirming resolution or agreement

Be proactive in correcting transaction errors before they escalate into disputes:

• Monitor your transaction logs and refund activity regularly for inconsistencies
  
  
• Respond quickly to cardholder inquiries to resolve issues without Amex intervention

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