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CO-B8 Denial Code: Alternative Service Should Be Used

CO-B8 means the payer determined that alternative services were available and should have been used instead of the service billed. The payer considers a different, usually less costly or less intensive, option appropriate for the patient's condition.

Quick facts

Code
CO-B8 (CARC B8)
Status
Active In use since January 1, 1995; last modified July 1, 2017.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The usual group. The provider absorbs the denied or reduced amount unless an appeal succeeds.
  • PR (Patient Responsibility): Used when the patient is liable, typically after being told in advance that the plan would only cover the alternative and choosing the billed service anyway.
Official description
Alternative services were available, and should have been utilized. Usage: Refer to the 835 Healthcare Policy Identification Segment (loop 2110 Service Payment Information REF), if present.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-B8 means

CARC B8 says alternative services were available, and should have been utilized. The payer is not questioning whether the patient needed care. It’s saying a different service would have met the need, and its policy expected that option first.

Typical alternatives include a less intensive level of care, a lower-cost setting, a conservative treatment before a procedure, a preferred drug or device, or standard equipment instead of a deluxe model. The usage note points to the 835 Healthcare Policy Identification segment, where the payer may name the policy that defines the alternative.

Example: a payer’s policy covers an advanced imaging study only after plain films. The advanced study is billed without documentation of prior imaging, and the line returns CO-B8.

Common causes

  • Step therapy or conservative care not documented, such as physical therapy or medication trials before a procedure.
  • Higher level of care chosen when the payer’s criteria support a lower one.
  • Deluxe or upgraded equipment when standard equipment meets the medical need.
  • Non-preferred drug used without documenting why the preferred option was unsuitable.
  • Site-of-service preferences, where the payer favors a lower-cost setting.

How to fix it

  1. Identify the alternative the payer expected, using the remark codes and policy reference.
  2. Review the record for evidence that the alternative was tried, contraindicated, or unsuitable.
  3. Appeal with that evidence, addressing each policy criterion. A letter of medical necessity from the treating clinician helps.
  4. Request peer-to-peer review where available.
  5. If the documentation doesn’t support the billed service, accept the denial. Write off CO amounts; bill PR amounts only when the patient accepted responsibility in advance.

How to prevent it

  • Check payer policies for step therapy and preferred alternatives before scheduling.
  • Document prior treatments and why alternatives were ruled out in the note.
  • Request prior authorization where the payer offers it, so the alternative question is settled before the service. See authorization and referral denials.
  • Give patients written notice when they choose a non-preferred option, following payer rules.

Specialty notes

DME suppliers see CO-B8 when upgraded items are billed without documentation that standard items won’t work. Behavioral health programs see it when a higher level of care, such as intensive outpatient, is billed and the payer believes routine outpatient care was adequate.

Remark codes that may appear with CO-B8

  • N130 (Consult plan benefit documents/guidelines for information about restrictions for this service.): Directs you to plan documents that describe the preferred alternative.
  • N661 (Documentation does not support that the services rendered were medically necessary.): Documentation doesn't support that the billed service was medically necessary instead of the alternative.
  • CO-169 (Alternate benefit has been provided.): An alternate benefit was provided: the payer paid for the alternative rather than denying outright.
  • CO-50 (These are non-covered services because this is not deemed a 'medical necessity' by the payer.): A general medical necessity denial.
  • CO-58 (Treatment was deemed by the payer to have been rendered in an inappropriate or invalid place of service.): The place of service was inappropriate, a setting-specific version of the same idea.
  • CO-56 (Procedure/treatment has not been deemed 'proven to be effective' by the payer.): The treatment isn't considered proven effective.

CO-B8 FAQ

What's the difference between CO-B8 and CO-169?

With CO-169, the payer pays the benefit for an alternative service, so you receive some payment. With CO-B8, the payer says the alternative should have been used and typically denies or reduces the billed service.

How do I appeal CO-B8?

Show why the alternative wasn't appropriate for this patient: contraindications, failed prior trials of the alternative, clinical findings, or safety concerns. Tie your evidence to the payer's policy criteria.

Can I bill the patient for CO-B8?

Not under the CO group code. If the payer reports PR, or the patient agreed in writing in advance under the payer's rules, you may bill the patient.

Does CO-B8 apply to drugs?

It can. Payers often require a preferred or generic drug, or a step therapy sequence, before covering another option. Check the payer's formulary and step therapy rules.