CO B8 denial code

Claim adjustment reason code B8. Often reported as CO B8 or PR B8.

A less costly alternative was available

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 B8 means

The payer decided a cheaper service would have met the patient's needs, so it denied or reduced payment for the one billed.

B8 is a least costly alternative decision. The payer does not dispute that care was needed, but believes a different, less expensive item or service would have been appropriate, and limits payment on that basis.

It is common with durable medical equipment, drugs and some procedures. A policy reference may come with it on the remittance, which tells you which coverage rule the payer applied.

Group codes seen with B8

On a remittance, B8 comes after a group code. These are the ones it is most often reported with:

• CO B8 (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.
• PR B8 (Patient Responsibility): The amount is assigned to the patient. Deductibles, coinsurance and copays are the everyday examples. Whether you can collect it still depends on your contract and the patient's plan.

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 higher level item was supplied when the payer's policy covers a basic model for the condition.
• A brand drug or premium product was billed where a lower cost equivalent is covered.
• The records did not explain why the less costly option was not suitable.

What to do next

1. Read the payer's coverage policy for the item or service to see which alternative it covers.
2. Gather documentation that shows why the less costly alternative was not appropriate for this patient.
3. Appeal with that documentation if the billed service was medically necessary.
4. Check whether an advance notice of patient liability was signed before billing the patient for the difference.

Related codes

• 50 (reason code) Not medically necessary per the payer
• B22 (reason code) Adjusted based on the diagnosis