12 | Invalid transaction
This code indicates the issuer or network rejected the authorization because the transaction type or parameters were not acceptable as presented.
What This Code Means
Response code 12 (“Invalid transaction”) is returned when the authorization request is not valid for processing under the issuer’s or network’s rules for that transaction type. This can relate to the transaction category, the method of authorization, or how the merchant system submitted the request. The code indicates a mismatch between expected transaction structure and what was presented, rather than a lack of funds. It is not a statement about the cardholder’s account balance. It also does not automatically imply the card is invalid; it indicates the transaction itself was not acceptable for authorization in that form.
Where Users Usually See This Code
- Payment gateway logs for declined authorizations
- POS terminal decline messages showing “Invalid transaction”
- Processor reporting dashboards listing response codes
Why This Code Appears
- Transaction type not permitted for the account or merchant configuration
- Authorization request parameters did not match expected standards
- Entry method or transaction category was rejected by issuer rules
- Network or issuer validation flagged the request as not processable
What Typically Happens Next
- Authorization is declined and the transaction does not settle
- Merchant system may record a technical decline category
- Subsequent attempts may continue to fail if the request structure remains unchanged
What This Code Is Not
- It is not a specific invalid card number response (see 14)
- It is not an insufficient funds outcome (see 51)
- It is not a generic issuer risk decline (see 05)
Troubleshooting Checklist
- □ Review the transaction attributes recorded by the gateway (type, entry method, and merchant category)
- □ Compare against successfully approved transactions to identify differences in request structure
- □ Document the decline code for support and reconciliation
- □ Follow official processor support workflows if repeated invalid transaction declines occur
Notes And Edge Cases
“Invalid transaction” can be used when an issuer expects a different transaction flow (for example, certain authorization types, reversals, or specialized merchant categories). Merchant-side configuration differences can influence the likelihood of this response. The same card may be approved for standard retail purchases but return 12 in unusual transaction flows. Some processors also map certain network validation failures into code 12 for reporting consistency.