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MA34 Remark Code: Invalid Number of Coinsurance Days

MA34 means the number of coinsurance days during the billing period is missing, incomplete, or invalid. Coinsurance days are covered days on which the patient owes a daily coinsurance amount, so the payer needs the correct count to calculate cost-sharing.

Quick facts

Code
MA34 (RARC MA34)
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 facility must correct the claim before cost-sharing can be calculated. The patient should not be billed based on the invalid count.
Official description
Missing/incomplete/invalid number of coinsurance days during the billing period.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What MA34 means

Medicare Part A covers a hospital or skilled nursing stay in stages within a benefit period. Early days carry no daily coinsurance, later days do, and beyond that the benefit may be exhausted. MA34 tells you the claim’s count of days in the coinsurance stage was missing or inconsistent.

The count depends on how many days the patient had already used in the benefit period, including at other facilities, which is why it is easy to get wrong.

Common causes

  • Coinsurance days were not reported although the stay crossed into the coinsurance range.
  • The count did not account for days the patient used at another facility in the same benefit period.
  • Coinsurance days exceed the covered days reported on the claim.
  • Coinsurance days were reported on a claim where none applied.

How to fix it

  1. Check the patient’s benefit period and prior days used through eligibility.
  2. Recalculate coinsurance days for this claim’s covered days.
  3. Report the count with the correct value code.
  4. Resubmit the claim, as an adjustment if the original was processed.

How to prevent it

Pull benefit-period data at admission and again before billing long stays, since other facilities’ claims may post in between. See eligibility and COB denials for how eligibility data prevents downstream errors.

Codes that may appear with MA34

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Claim data is missing or invalid, with MA34 pointing to coinsurance days.
  • MA32 (Missing/incomplete/invalid number of covered days during the billing period.): The covered day count is missing or invalid.
  • MA35 (Missing/incomplete/invalid number of lifetime reserve days.): Lifetime reserve days are missing or invalid, a different Part A day type.
  • PR-2 (Coinsurance Amount): The coinsurance amount itself, calculated once the day count is accepted.

MA34 FAQ

When do coinsurance days apply?

Under Medicare Part A, daily coinsurance applies after a set number of covered days in a benefit period, both for hospital stays and for skilled nursing facility stays. The day thresholds differ by setting.

How are coinsurance days reported?

On the UB-04 they are reported as a value code in form locators 39 to 41. Medicare uses value code 82 for coinsurance days.

Where does the payer get the patient's prior days?

From its benefit records for the patient's benefit period. If your count disagrees, check eligibility data for days used on earlier stays.