N56 remark code

Remittance advice remark code N56. Remark codes add detail to the reason code on the same claim line.

Procedure code invalid for service or date

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What N56 means

The payer says this code either does not describe the work documented or was not an active code when the service was done.

N56 points at the code itself. It may be a code that was deleted or not yet effective on that date, or one that the payer does not see as correctly describing what was done.

It normally supports a reason code such as 181 or 16. Check annual code updates first, since many N56 denials come from claims billed with retired codes early in a new year.

Common causes

• A deleted code was billed after its end date, or a new code before its effective date.
• The code does not fit the patient's age, sex or the type of claim.
• The charge master still maps the service to an outdated code.

What to do next

1. Look up the code's effective and termination dates for the date of service.
2. Confirm with the coder which current code describes the service.
3. Submit a corrected claim with the valid code.
4. Update the charge master or fee schedule so the old code is no longer used.

Related codes

• N657 (remark code) Bill with the right code
• N65 (remark code) Payer could not price the code
• 16 (reason code) Missing information or billing error