Tip from SmartRetry Halt immediate automated retries on code 30, as repeating an identical payload will consistently fail and can trigger network penalty flags. Instead, hold the retry until your system applies automated character sanitization or reroutes the payment through a verified secondary acquirer connection.
Mastercard
Mastercard Decline Code 30: Format Error
technical decline
Last updated: September 25, 2026
About 30 - "Format error"
Key details
- 30
- Issuer Response Codes
- 30
- Format error
technical decline
What it means
Mastercard issuer response code 30 indicates that the issuer does not recognize the transaction details presented in the authorization request. It is a technical formatting or configuration error, most commonly triggered by an incorrect terminal ID (TID) or the presence of invalid characters in the transaction data. This decline is not related to the cardholder's available funds.
Classification & retryability
technicalRetryable: conditional
Code 30 is classified by Mastercard as 'Temporarily Recoverable,' meaning a corrected request can be retried. However, you must first fix the terminal ID (TID), formatting, or transaction fields before initiating the retry, as repeating the identical authorization will likely result in another decline.
Why does code 30 occur?
- The transaction request contains an incorrect or unregistered terminal ID (TID).
- The authorization payload includes malformed or invalid characters that the issuer cannot process.
- There is a persistent merchant integration or mapping defect causing improper transaction data formatting.
How to solve 30?
First, review the original authorization request to verify that the terminal ID (TID) and merchant identifier match your acquirer's registered configuration. Check the transaction data payload for any malformed fields, invalid characters, or encoding errors. Once the formatting or configuration errors are identified and corrected, submit a new authorization request. If subsequent attempts fail after corrections, escalate the issue to your acquirer or processor with the original request, response, TID, and transaction timestamp.
Solving as a merchant
Compare the submitted request with your acquirer's registered merchant and terminal configuration to validate field encoding, allowed characters, and routing parameters. Correct any improperly formatted data or incorrect TIDs in your payment gateway settings before attempting a retry. Suppress repeated identical attempts to avoid accumulating unnecessary declines.
Solving as a customer
No action is required from the customer, as this is a technical formatting issue on the merchant or processor side.
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Author
Kyle Regacho
Find me on LinkedinFocused on payment recovery, decline codes, and authorization optimization at SmartRetry. Helps payment teams turn failed transactions into recovered revenue
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