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N128 Remark Code: Prior-to-Coverage Portion of Allowance

N128 means the adjusted amount is the portion of the allowance attributable to the time before the patient's coverage started. The payer paid or considered only the part of the service that fell within coverage and separated out the prior-to-coverage portion.

Quick facts

Code
N128 (RARC N128)
Status
Active In use since October 31, 2002.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • PR (Patient Responsibility): The prior-to-coverage portion is usually the patient's responsibility, or belongs to whatever coverage the patient had before this plan began.
  • CO (Contractual Obligation): Less common. Used if a contract or regulation prevents the provider from billing the patient for that portion.
Official description
This amount represents the prior to coverage portion of the allowance.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N128 means

Some claims cover a range of dates rather than a single day. If the patient’s coverage with this payer started in the middle of that range, the payer can only take responsibility for the covered days. N128 labels the amount it carved out for the days before coverage began.

It usually appears with CARC 26 or CARC 238 and most often with a PR group code.

Common causes

  • A monthly rental or recurring service was billed for a period that began before the effective date.
  • An inpatient or facility stay started before the patient enrolled, for example when coverage began mid-stay.
  • The effective date on the payer’s file differs from what the patient reported at registration.
  • A retroactive enrollment set an effective date later than expected.

What to do

  1. Confirm the effective date with a current eligibility response and compare it with the claim’s service period.
  2. Check for earlier coverage. If the patient had another plan or public program for the earlier dates, bill it for the carved-out portion.
  3. If the effective date on file is wrong, ask the patient or employer to have it corrected, then request reprocessing.
  4. Otherwise, bill the patient for the prior-to-coverage amount shown on the remittance.

How to prevent it

When a patient’s coverage is new, verify the exact effective date before billing any service that spans dates. Aligning rental cycles or billing periods to coverage start dates avoids most N128 splits. The eligibility guide covers effective-date verification.

Codes that may appear with N128

  • PR-26 (Expenses incurred prior to coverage.): Expenses incurred prior to coverage.
  • PR-238 (Claim spans eligible and ineligible periods of coverage, this is the reduction for the ineligible period. (Use only with Group Code PR)): The claim spans eligible and ineligible periods; this is the reduction for the ineligible period.
  • CO-239 (Claim spans eligible and ineligible periods of coverage.): The claim spans eligible and ineligible periods and must be rebilled as separate claims.
  • N144 (The rate changed during the dates of service billed.): Explains that the rate changed during the billed dates of service, another reason a spanning claim is split.
  • PR-27 (Expenses incurred after coverage terminated.): Expenses incurred after coverage ended, the mirror image of the prior-to-coverage problem.

N128 FAQ

How can one service have a prior-to-coverage portion?

It happens with services billed over a span of dates, such as a monthly rental, a stay, or a global period, where coverage started partway through the span.

Who should I bill for that portion?

The patient's prior coverage, if they had any for those dates, or the patient. Check eligibility for the earlier dates first.

Should I split the claim?

If the payer's rules require separate claims for covered and uncovered periods, yes. Otherwise the payer's split on the remittance may be enough.