CO 182 denial code

Claim adjustment reason code 182. Often reported as CO 182.

Modifier invalid on date of service

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 182 means

A modifier on the claim was not valid on the date the service was provided.

Modifiers are added and retired just like procedure codes. This code means a modifier on the line was not active on the date of service, or is not accepted by the payer for that date.

Check every modifier on the line, since any one of them can trigger this.

Group codes seen with 182

On a remittance, 182 comes after a group code. These are the ones it is most often reported with:

• CO 182 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• A retired modifier was used after its end date.
• A new modifier was used for a date before the payer accepted it.
• A typo produced a modifier that does not exist.

What to do next

1. Check each modifier on the line against the code set in effect on the date of service.
2. Replace or remove the invalid modifier and resubmit a corrected claim.
3. Update modifier tables and charge rules in your billing system.

Related codes

• 181 (reason code) Procedure code invalid on date of service
• 4 (reason code) Procedure code and modifier do not match