CO 5 denial code

Claim adjustment reason code 5. Often reported as CO 5.

Code does not fit the place 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 5 means

The procedure code or bill type does not match the place of service on the claim, so the payer would not process it as billed.

The payer checked the service against where it was performed and found a conflict. Some codes are only valid in a facility, some only in an office, and a type of bill on an institutional claim also has to agree with the setting.

It is most often a CO adjustment that a corrected claim can fix. Look for a line level policy reference on the 835; it identifies the edit or policy the payer used.

Group codes seen with 5

On a remittance, 5 comes after a group code. These are the ones it is most often reported with:

• CO 5 (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

• The place of service code was defaulted from the provider's main location instead of where the patient was seen.
• A facility only code was billed with an office place of service, or the reverse.
• The type of bill on an institutional claim does not agree with the setting of care.
• A telehealth service was billed with a place of service the payer does not accept for it.

What to do next

1. Confirm where the service took place from the encounter record and registration data.
2. Correct the place of service code or type of bill and send a corrected claim.
3. Check the payer's place of service rules for telehealth or split facility settings.
4. Fix the default place of service in the practice management system if it caused the error.

Related codes

• 58 (reason code) Wrong or invalid place of service
• 4 (reason code) Procedure code and modifier do not match
• 16 (reason code) Missing information or billing error