Response Code 55: Incorrect PIN
PIN verification failed. Multiple attempts may lock the card.
What Does Code 55 Mean?
Response code 55 means the PIN entered by the cardholder does not match the PIN on file with the issuer. This code only applies to PIN-based transactions (debit card purchases, ATM withdrawals) and should not appear in standard e-commerce flows where CVV is used instead of PIN.
If you're seeing code 55 in an online transaction, something is misconfigured in the POS Entry Mode (Field 22). E-commerce transactions should use mode 051 (manual key entry, no PIN capability), which tells the issuer not to expect a PIN. Automated retries on code 55 are counterproductive because multiple failed PIN attempts will lock the card entirely.
Why You Should Not Retry
Do not auto-retry. Prompt the cardholder to re-enter their PIN.
Common Causes
- Cardholder entered the wrong PIN
- Cardholder forgot their PIN after a card replacement
- POS Entry Mode misconfigured to request PIN verification in a card-not-present environment
Network Behavior
The same response code can mean different things depending on the card network. Here is how each network treats Code 55:
Platform Mappings
This code surfaces under different names depending on the payment platform:
| ISO 8583 | 55 - Incorrect PIN |
| Stripe | incorrect_pin |
Related Decline Codes
See This Code in Action
Watch how response code 55 flows through a complete ISO 8583 authorization lifecycle.
Open Transaction Simulator