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M78 Remark Code (Deactivated): HCPCS Modifier Invalid

M78 meant a HCPCS modifier on the claim was missing, incomplete, or invalid. X12 deactivated it and suggested reason code 4; remarks N822 and N823 now cover missing and invalid modifiers.

X12 deactivated RARCM78 on May 18, 2006. Payers should no longer use it on new remittances, but it can still appear on older ERAs, corrected claims, and appeals.

Code: M78 (RARC M78)
Status: Deactivated StoppedMay 18, 2006 (in use since January 1, 1997).
Code set: Remittance Advice Remark Codes (RARC)
Group codes: CO (Contractual Obligation): Modifier errors are the provider's to correct, so the related adjustment was under CO.
Official description: Missing/incomplete/invalid HCPCS modifier.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What M78 meant

Remark M78 covered modifier problems. A modifier the payer needed was absent, or the one reported was incomplete or not valid. Since modifiers can change payment or indicate that a service was distinct, a missing or bad one often stopped the claim.

What replaced it

X12’s note suggests reason code 4. CO-4 says the procedure code is inconsistent with the modifier used. Active remarks now separate the details: N822 for a missing modifier, N823 for an incomplete or invalid one, and N519 for an invalid combination of modifiers.

If you still see M78

It was retired long ago, so it should only turn up in old files. For a modifier denial now, check the payer’s policy for the procedure, confirm each modifier is valid for the date of service, and verify the order and combination. Correct the claim and resubmit it as a corrected claim.

CO-4 (The procedure code is inconsistent with the modifier used.): The suggested replacement: procedure code inconsistent with the modifier used.
N822 (Missing procedure modifier(s).): Missing procedure modifier.
N823 (Incomplete/Invalid procedure modifier(s).): Incomplete or invalid procedure modifier.
N519 (Invalid combination of HCPCS modifiers.): Invalid combination of HCPCS modifiers.

M78 FAQ

What kinds of modifier errors trigger these remarks?

A required modifier left off, a modifier that does not exist or is not valid on the date of service, one that does not fit the procedure, or two modifiers that cannot be combined.

Was M78 itself suggested as a replacement for anything?

Yes. X12 pointed to M78 in place of M101, an earlier remark about reporting certain modifiers on specific HCPCS codes.

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