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MA35 Remark Code: Invalid Lifetime Reserve Days

MA35 means the number of lifetime reserve days on the claim is missing, incomplete, or invalid. Lifetime reserve days are a limited pool of extra Medicare inpatient hospital days, so the payer must know exactly how many this stay uses.

Quick facts

Code
MA35 (RARC MA35)
Status
Active In use since January 1, 1997; last modified February 28, 2003.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The hospital must correct the reporting. The patient is not billed for a claim returned over a day-count error.
Official description
Missing/incomplete/invalid number of lifetime reserve days.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What MA35 means

When a long hospital stay goes past the regular days available in a Medicare benefit period, the patient can draw on lifetime reserve days. Because these days are a one-time allowance, the payer tracks them carefully. MA35 says the claim’s lifetime reserve day count was absent or did not fit, for example because it exceeded the patient’s remaining reserve or conflicted with the covered and coinsurance days reported.

It only arises on inpatient hospital claims for long stays, so it is uncommon but can be costly to fix late.

Common causes

  • The stay extended into lifetime reserve days but no count was reported.
  • More reserve days were claimed than the patient has left.
  • The patient elected not to use reserve days, but the claim reported them anyway, or the reverse.
  • The count was not reconciled with covered and coinsurance days.

How to fix it

  1. Check remaining reserve days through eligibility data.
  2. Confirm the patient’s election about using reserve days and keep a signed record.
  3. Recalculate and report the correct count using the appropriate value code and any required condition code.
  4. Resubmit the corrected claim through the payer’s adjustment process.

How to prevent it

Flag long inpatient stays early, confirm the patient’s remaining reserve days, and document their election before the claim is built. Long stays merit a pre-billing review; tools like a Claims Validator help catch day-count conflicts.

Codes that may appear with MA35

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Required claim data is missing or invalid, with MA35 naming lifetime reserve days.
  • MA34 (Missing/incomplete/invalid number of coinsurance days during the billing period.): Coinsurance days are missing or invalid, the stage before lifetime reserve days.
  • MA32 (Missing/incomplete/invalid number of covered days during the billing period.): Covered days are missing or invalid.
  • CO-149 (Lifetime benefit maximum has been reached for this service/benefit category.): The lifetime benefit maximum has been reached.

MA35 FAQ

What are lifetime reserve days?

Under Medicare Part A, they are extra inpatient hospital days a beneficiary can draw on after regular benefit-period days are used up. Once used, they do not renew.

Can a patient choose not to use them?

Yes. A beneficiary can elect not to use lifetime reserve days for a stay, and that choice must be reflected on the claim according to Medicare instructions.

How are they reported?

On the UB-04 they are reported as a value code in form locators 39 to 41. Medicare uses value code 83 for lifetime reserve days.