CO 188 denial code

Claim adjustment reason code 188. Often reported as CO 188.

Not used per FDA recommendations

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 188 means

The product or procedure is covered only when used as the FDA recommends, and this use did not meet that.

The payer covers this drug, device or procedure only for uses that follow FDA labeling or recommendations. This claim showed a use outside that, such as an off-label indication or dose.

Some payers accept other evidence for off-label use. Check the payer's policy before appealing.

Group codes seen with 188

On a remittance, 188 comes after a group code. These are the ones it is most often reported with:

• CO 188 (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 drug or device was used for a condition outside its FDA labeling.
• The dose or route did not follow the FDA labeling.
• The diagnosis on the claim did not match an approved use.

What to do next

1. Check the diagnosis and dose on the claim against the product's approved uses.
2. Correct the claim if the diagnosis or dose was coded wrong.
3. Appeal with supporting clinical evidence if the payer's policy allows off-label coverage.

Related codes

• 153 (reason code) Records do not support dosage
• 50 (reason code) Not medically necessary per the payer