MA66MA-series (Medicare alerts & claim-level)Missing Information
MA66: Principal procedure code missing or invalid
The principal procedure code on an institutional claim is missing or invalid — required when a significant procedure was performed.
Commonly appears with these denial codes
The denial code gives the category; MA66 pinpoints the specific problem. Read them together before touching the claim.
What to do about it
Report the principal procedure (ICD-10-PCS for inpatient) with the correct date, and resubmit.
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