What does denial code CO-4 mean?

Procedure code inconsistent with the modifier, or a required modifier is missing. The payer expected a different modifier, or a modifier that is required for this code was not on the claim.

How do I fix a CO-4 denial?

Check the payer's modifier rules for the code. Add or correct the modifier and send a corrected claim.

Pricing

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Claim adjustment reason code · Contractual obligation

CO-4
Procedure code inconsistent with the modifier, or a required modifier is missing

What CO-4 means

The payer expected a different modifier, or a modifier that is required for this code was not on the claim.

The CO group code means this amount is a contractual obligation: under most contracts you cannot bill it to the patient.

Common causes

Missing modifier (for example 25, 59, GP, RT/LT)
Modifier that does not apply to the code billed

How to fix it

Check the payer's modifier rules for the code
Add or correct the modifier and send a corrected claim

Check the remark code (RARC) that came with the denial and the payer's own policy, since rules vary by payer and plan. This is a plain-English summary written by GetMax; the official code text is published by X12 at x12.org/codes.

Prevent it next time

Most denials are caused before the claim is sent. See 12 ways to reduce claim denials, or let our denial management team work them for you.

Other codes

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CO-4Procedure code inconsistent with the modifier, or a required modifier is missing