13 | Invalid amount
This code indicates the authorization was declined because the amount in the request was not acceptable under issuer or network rules.
What This Code Means
Response code 13 (“Invalid amount”) is returned when the transaction amount submitted for authorization fails validation rules. This can mean the amount is outside allowable ranges, contains formatting issues, or conflicts with the merchant’s or issuer’s expectations for that transaction type. The code is about the amount field and how it is presented, not the account’s available funds. It does not indicate that the card is invalid. It also does not automatically imply the amount is “too high” in a funds sense; it indicates the amount value is not acceptable for processing as submitted.
Where Users Usually See This Code
- Merchant gateway decline logs
- POS terminal decline messages
- Processor reporting that categorizes declines by response code
Why This Code Appears
- Amount value failed validation (formatting, precision, or allowed range)
- The authorization amount was inconsistent with the transaction type
- The merchant request included an amount that issuer rules reject for that context
- Network validation flagged the amount field as not acceptable
What Typically Happens Next
- Authorization is declined and the transaction does not complete
- Merchant system records the decline code associated with the amount field
- Retrying with the same parameters may produce the same result
What This Code Is Not
- It is not an insufficient funds decline (see 51)
- It is not an invalid card number response (see 14)
- It is not a generic issuer “do not honor” (see 05)
Troubleshooting Checklist
- □ Review the amount formatting and currency context in the authorization request logs
- □ Compare failed requests to recent successful transactions for consistency
- □ Document the code for reconciliation and support handling
- □ Use official processor support channels for repeated amount-validation declines
Notes And Edge Cases
Some transactions involve preauthorizations, incremental authorizations, or reversals where the amount behavior differs from standard purchases. In those flows, issuer or network rules may reject amount values that are valid in other contexts. Currency handling and rounding can also influence validation in certain environments. The decline code alone does not identify which validation rule failed, so gateway logs and transaction metadata are typically needed to isolate patterns.