Which denial codes appear with N56?

N56 commonly rides with CO 16, CO 4. The adjustment code says the claim was reduced; the remark code says why.

Remark code

N56 denial code

The procedure code does not match what was done, or was not valid on that date of service.

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.

What to do

Check the code against the DATE, not against today. Code sets change every January, and a claim for December work submitted in February is judged on the December set.

Codes it appears with

N56 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.

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