N556 Remark Code: Medication List Incomplete or Invalid
N556 means the payer received a medication list but found it incomplete or invalid. It may be missing doses, frequencies, or dates, may be outdated or unsigned, or may not correspond to the patient or date of service on the claim.
Quick facts
- Code
- N556 (RARC N556)
- Status
- Active In use since July 1, 2012.
- Code set
- Remittance Advice Remark Codes (RARC)
- Group codes
-
- CO (Contractual Obligation): The adjustment reflects deficient documentation the provider can correct. It is not billed to the patient.
- Official description
Incomplete/invalid medication list.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026- Last verified
- against the official X12 list.
What N556 means
The medication list reached the payer, but the reviewer could not accept it. N556 is the incomplete-or-invalid counterpart to N555. When a service depends on reviewing or reconciling medications, the list has to show the drugs, how they are taken, and that it reflects the patient’s status on the date billed.
What reviewers look for
| Element | Typical problem |
|---|---|
| Drug detail | Name only, with no strength, dose, route, or frequency |
| Date | No review date, or a list from a different encounter |
| Identifiers | Missing patient name, date of birth, or member ID |
| Reviewer | No indication of who reviewed or reconciled the list |
| Relevance | The list does not relate to the service or date billed |
How to fix it
- Find the specific deficiency in the payer’s notice or by calling.
- Locate the right version of the list documented on or around the date of service.
- Resend the correct document, labeled with patient identifiers, dates of service, and the claim number.
- Address documentation gaps honestly. If the list was never complete, follow your organization’s addendum policy rather than editing the original.
- Request reprocessing or file a reconsideration, as the payer directs.
How to prevent it
Use a structured medication list in the EHR that requires dose, route, and frequency for each entry and records who reviewed it and when. When sending records, export the version tied to the billed encounter rather than the current list.
Codes that may appear with N556
- CO-251 (The attachment/other documentation that was received was incomplete or deficient.): The attachment was received but was incomplete or deficient.
- CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim contained invalid information needed for adjudication.
- CO-250 (The attachment/other documentation that was received was the incorrect attachment/document.): The payer received a document, but not the one it expected.
Related and easily confused codes
- N555 (Missing medication list.): No medication list was received.
- N730 (Incomplete/invalid patient medical/dental record for this service.): Incomplete or invalid patient medical or dental record for this service.
- N206 (The supporting documentation does not match the information sent on the claim.): The supporting documentation does not match the information on the claim.
N556 FAQ
What makes a medication list invalid?
Common issues are missing dose or frequency, no date showing when it was reviewed, a list from a different encounter, missing patient identifiers, or no indication of who reviewed it.
Can I update the list now and resend it?
You should not alter the historical record. If the original documentation was incomplete, you may add a properly dated late entry or addendum under your organization's policy, but the payer may weigh it differently than contemporaneous notes.
Is N556 a medical necessity denial?
No. It is a documentation problem. The payer could not evaluate the service with the list it received.