Which denial codes appear with M51?

M51 commonly rides with CO 16, CO 4. The adjustment code says the claim was reduced; the remark code says why.

Remark code

M51 denial code

A procedure code is missing, incomplete or not valid.

A correction, not an appeal

A remark code is not the denial. The adjustment code says the claim was reduced. This one says why. You need both to know what to send back.

Check the code against the DATE of service rather than today, because code sets change every January. Correct and resubmit.

M51 commonly rides alongside these. Our reading, not a published mapping: X12 publishes no adjustment-to-remark table.

Code	What that one means
CO 16	Something the payer needed was missing or wrong on the claim.
CO 4	The procedure code and the modifier do not agree.

Upload your denial export 4 columns. No patient data. One page back.