Understanding American Express Chargeback Reason Code A02: No Valid Authorisation

American Express Reason Code A02 means a transaction was processed without valid authorisation. It may be due to a decline being ignored, an expired card, or a mismatch between the authorisation and the submitted charge. Understanding the causes, the time limit, and how to respond or fight the claim helps merchants protect revenue.

Key Takeaways

• What it means: The charge was processed without valid authorisation or with an expired card.
• Causes: Forced transactions. Bypassed requests. Mismatched data. Using an expired card.
• How to respond: Provide proof of authorisation, valid card dates, or evidence of a refund.
• How to prevent: Always request authorisation. Respect declines. Keep accurate records.

What is an American Express Reason Code A02 Chargeback?

Reason Code A02, “No Valid Authorisation,” is raised when a transaction reaches settlement without an approved authorisation that matches the charge. The issuer believes the payment should not have been processed. This can happen if the merchant bypasses authorisation, pushes a declined transaction through, or accepts a card past its expiry date. It can also occur when the authorisation details do not align with the settled transaction. 

A02 flags a breakdown in the authorisation flow that underpins payment risk decisions, suggesting that an operational or system step failed at the point of sale or gateway. The rule is clear: no valid authorisation means no guarantee of payment. To resolve an A02 dispute, the merchant must provide a valid authorisation approval for the transaction. Another valid reason for overturning a claim is proving that the charge was already reversed via a refund.

Primary Causes for a Code A02 Chargeback

Several common causes sit behind A02. The most obvious is forcing a transaction after receiving a decline response. Some systems allow a “voice” or “force” function. Using this to override a decline, without a valid approval code, exposes the merchant to an A02 dispute. Another frequent cause is submitting a charge that does not match its authorisation. If the authorisation was for a different amount, date, or merchant ID, the issuer may treat the settled item as unauthorised.

Expired cards are a common trigger for this reason code. If the transaction date is after the card’s expiry, the issuer may challenge the payment. Data quality errors also matter. Transposed numbers, the wrong authorisation code, or referencing an approval from a separate transaction can all lead to a mismatch. In some sectors, timing rules apply. For example, aggregated contactless transit charges must be authorised within defined windows. Missing those windows can prompt A02. Finally, manual key entry, fallback from chip to magstripe, or gateway outages can tempt staff to skip the request. Each shortcut carries a high risk and can lead directly to this chargeback.

Time Limit for Disputing an American Express Reason Code A02 Chargeback

The time limit is tight. American Express sets a 20‑day window for the acquirer or merchant to submit a response to an A02 dispute. This clock does not start when you read the notice; it starts when Amex sends it. It also includes the time your acquirer takes to forward the case and review your evidence. In practice, merchants often have only a few days to gather documents and respond. Treat A02 notices as urgent.

Mark the deadline on receipt and start evidence collection immediately. Where possible, pull system logs automatically. Include the authorisation approval code, date and time of the request, terminal ID, and ARQC/ARC data for chip transactions. If the card expiry is in question, retrieve a copy of the transaction record showing the card’s valid dates and the transaction timestamp. 

If you have already issued a refund, include proof of the credit posting. Keep your files structured so you can produce proof on short notice. Missing the time limit usually results in an automatic loss, chargeback fees, and no second chance to contest. Swift action helps protect revenue and shows strong process discipline.

What A02 Means for Consumers & Issuers

A02 allows a cardholder to challenge charges that appear to have been processed without a proper authorisation or with an expired card. Many disputes arise from confusion or error, such as a staff member keying the wrong amount or a system retrying a declined payment. Others involve genuine unauthorised activity. From the cardholder’s view, A02 asks a simple question: was this transaction authorised correctly? If not, liability shifts away from them.

For issuers, A02 reinforces compliance with authorisation rules. Issuers review authorisation logs, compare approval codes to clearing data, and verify that timing and expiry rules were followed. They may also consider sector‑specific exceptions, such as delayed charges or aggregated contactless journeys. When evidence does not support proper authorisation, the issuer can return the charge. A02 is not a judgment on service quality; it is a rules‑based finding about payment validity.

What A02 Means for Merchants

For merchants, A02 is a warning sign that the authorisation step broke down. The financial hit includes the principal amount plus any dispute fees. Higher processing scrutiny and potential impact on acceptance if problems persist add to the impact. Operationally, A02 highlights process gaps, including:

• Staff overriding declines rather than asking for another payment method
• Terminals reverting to unsafe paths
• Gateways resubmitting charges without a fresh authorisation
• Mismatched settlement files, where the charge details do not match the original approval

A02 disputes waste time and distract teams from their core responsibilities. They also erode trust with customers who see unexpected charges. Repeated A02s may trigger reviews by American Express, leading to requests for corrective action. Treat A02 as a fixable compliance issue, not a cost of doing business.

How to Respond to a Code A02 Chargeback

Act quickly and structure your reply. First, confirm the time limit and assign a case owner. Next, gather proof. To fight an A02 dispute, you generally need one or more of the following:

• The approval code, date/time stamp, and identifiers that match the settled transaction.
• Records showing the transaction took place before the card expiry date or within the card’s active window.
• Documentation showing a refund was processed before the chargeback.

For sectors with aggregated or delayed contactless activity, include evidence that authorisation was obtained within the allowed period. Or, prove that a fresh account status check was performed when required. Reconcile any differences between the authorisation and settlement data. If the authorised amount changed, document the reason and show a new approval for the final amount. 

Keep your narrative brief, factual, and aligned to the reason code. Avoid subjective commentary. Submit your package through your acquirer in the format they request. After filing, log the outcome and feed any insights into process improvements.

Proactive Prevention: The Ultimate Defence

Prevention is simpler than dispute management. Adopt clear rules: always request and receive a valid authorisation before charging; never push through a decline; and do not accept expired cards. If an amount, date, or merchant ID changes, get a new approval. Keep terminals updated, block unsafe fallback, and tighten gateway settings to stop “force” functions. Train staff to read authorisation responses and request an alternative payment method when necessary. Maintain accurate records so you can answer questions promptly.

Add real‑time tools to reduce risk and protect revenue. Alerts can notify you early when a cardholder questions a charge. That gives you the choice to refund quickly and avoid a chargeback. To add this capability to your workflow, try out Chargeback.io. Combine alerts with daily exception reporting and a monthly audit of authorisation logs. Together, these steps reduce A02 exposure and improve acceptance without adding friction for your customers.