RARC M77: Missing, Incomplete, Invalid, or Inappropriate Place of Service
RARC M77 means the place of service on the claim is missing, incomplete, invalid, or inappropriate for the procedure billed. It rides with CO-16 and is fixed by correcting the two-digit POS code — commonly a telehealth visit, facility service, or home visit billed under the default office POS 11.
- Type
- Informational (supplemental)
- Usually paired with
- CO-16
- Fixable?
- Yes — always
- Typical fix
- Correct the 2-digit POS to match where care actually happened
What does remark code M77 mean?
Official X12 text: "Missing/incomplete/invalid/inappropriate place of service." The two-digit POS code in box 24B (or its 837 equivalent) is either absent, not a real code, or contradicts the procedure billed. The payer will not guess where care happened, so the line bounces.
ERA mini-example: 99214-95 (telehealth E/M) billed $185.00 denies CO-16 with M77. The claim went out with POS 11 because the scheduler booked it as an office slot; the payer requires POS 10 for a video visit with the patient at home. Corrected claim, paid at the telehealth rate.
Which denial code does M77 come with?
Almost always CO-16, marking the claim unprocessable rather than denied on merits. Some payers use CARC 5 (procedure inconsistent with place of service) for the "inappropriate" flavor, which carries the same fix. Confirm the combination in the denial code lookup and review the POS code overview for the full set.
How do you fix an M77 denial?
- Confirm where the service physically happened — ask the provider or check the visit type, do not assume.
- Correct the POS: 11 office, 02/10 telehealth, 21/22 hospital settings, 12 home.
- Check modifier alignment: telehealth POS usually needs modifier 95 (or GT for some payers), and facility POS may shift the code to the facility fee schedule.
- Resubmit as a corrected claim.
How do you prevent M77?
Bind POS to the appointment type, not to a system default: telehealth visit types write POS 02/10, hospital rounds write 21, nursing facility visits write 31/32. Then add a scrubber rule flagging any telehealth modifier paired with POS 11 and any facility-only CPT paired with an office POS. Those two edits eliminate the vast majority of M77 volume in a typical clinic.
Frequently asked questions
Invalid means the field is blank or not a real POS code. Inappropriate means the code exists but conflicts with the service: an inpatient-only procedure billed POS 11 (office), a facility-based CPT billed in a home setting, or a telehealth modifier on a claim showing POS 21. The payer edit compares the CPT against the setting and rejects mismatches.
Because telehealth splits across POS 02 (telehealth, not in patient home) and POS 10 (telehealth in patient home), and payment can differ between them. EHR templates that default every encounter to POS 11 send virtual visits out as office visits — some payers deny with M77, others quietly pay the wrong rate, which is worse because nobody catches it.
Often yes. POS drives the facility versus non-facility rate: the same CPT typically pays more in POS 11 because the practice bears the overhead. Correcting POS 11 to POS 22 (on-campus outpatient) on a resubmission usually lowers the allowable. Bill the setting where care actually occurred — POS gaming is an audit magnet.
Sources & further reading
Reviewed by the ImmediCare Solutions RCM team
Certified billers and coders handling claims across 50+ specialties nationwide. This entry is reviewed against current payer policy and CMS rules. Last review: Jul 5, 2026.
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