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M43 Remark Code (Deactivated): Paid by Another Carrier

M43 meant payment for the service had already been issued, to you or another provider, by another carrier or intermediary. X12 deactivated it and its note suggests using CARC 23 instead.

X12 deactivated RARCM43 on January 31, 2004. Payers should no longer use it on new remittances, but it can still appear on older ERAs, corrected claims, and appeals.

Quick facts

Code
M43 (RARC M43)
Status
Deactivated StoppedJanuary 31, 2004 (in use since January 1, 1997).
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • OA (Other Adjustment): Often seen with other-adjustment codes, since the amount had been handled by another payer rather than written off contractually.
  • CO (Contractual Obligation): Some payers paired it with CO denials when they treated the claim as already settled.
Official description
Payment for this service previously issued to you or another provider by another carrier/intermediary.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M43 meant

Remark M43 explained a denial or zero payment because a different carrier or intermediary had already paid for the same service. That payment might have gone to the same provider through another channel, or to a different provider altogether.

What replaced it

X12’s note suggests reason code 23, so OA-23, the impact of prior payer adjudication, is the recommended approach. Other active options include CARC CO-B13 when payment may have been made on an earlier remittance, and remark N347 when payment for a referred or purchased service went to another provider.

If you still see M43

It is an early Medicare remark found only in old files. When investigating a similar situation today, search your own posting history for a payment from another contractor or payer for the same date and service. If none exists, ask the payer to identify who was paid, then coordinate with that provider or request correction.

  • OA-23 (The impact of prior payer(s) adjudication including payments and/or adjustments. (Use only with Group Code OA)): The suggested replacement: impact of prior payer adjudication.
  • CO-B13 (Previously paid.): Previously paid; payment may have been made in an earlier remittance.
  • N347 (Your claim for a referred or purchased service cannot be paid because payment has already been made for this same service to another provider by a…): Payment already made for this referred or purchased service to another provider.

M43 FAQ

Why would another carrier already have paid?

In Medicare, services can be billed to the wrong contractor, or a service billed by one provider may already have been paid to another under a different contractor. The remark told you payment had happened elsewhere.

Should I refile the claim?

Not without first confirming where the payment went. If it went to you, reconcile it; if to another provider, work out which provider should have billed.