AGAR Guide

Coordination of Benefits

AR Guide Knowledge

Primary/secondary payer order, COB adjustments, and claims that belong with another payer.

Denial Decoder

Run this denial through the decoder

Enter the codes from your ERA/EOB and get this workflow with the exact CARC/RARC on your line.

Open Denial Decoder

Check first

Check these before anything else

  • Order of benefits for the patient
  • The primary payer's EOB or ERA
  • Which payer was billed first
  • COB information currently on file
  • Plan type (medical / dental / pharmacy)
  • CARC 22 / 23 and the accompanying remark code

Verify payer-specific rules: Heads up

Coordination-of-benefits rules and the order-of-benefits determination are payer- and plan-specific. Confirm the correct order with the payers involved and attach the primary's EOB to secondary claims.

AR Guide knowledge

What it means

The claim involves multiple insurance plans and the payer is adjusting based on coordination-of-benefits rules — the wrong payer was billed first, the primary's payment was applied incorrectly, or the service is covered by another plan. COB denials are often fixable by billing the correct order of benefits or providing the primary's explanation of benefits.

AR Guide knowledge

Common causes

  • Patient has multiple plans and the primary was not billed first
  • COB information on file is missing or stale
  • Secondary claim processed before the primary's payment
  • Prior payer's payment applied incorrectly to patient responsibility
  • Claim belongs with a different plan type (medical, dental, pharmacy)

AR Guide knowledge

What AR should verify

  • Confirm the patient's insurance order of benefits
  • Check whether the primary payer has been billed and paid
  • Compare the primary payer's EOB or ERA with this adjustment
  • Verify COB information on file is current
  • Confirm the claim was submitted to the correct plan for the service

Recommended workflow

What to do next

  1. Bill the primary payer per the order of benefits
  2. Resubmit the secondary claim with the primary's EOB or ERA attached
  3. Update COB records if the coverage order has changed
  4. If the secondary calculation looks wrong, request a recalculation with the primary EOB

Don’t assume

Avoid these shortcuts

  • The payer billed is the primary
  • The primary has already paid
  • The COB information on file is current
  • The secondary denial is final — it may just need the primary's EOB
  • The two plans will coordinate automatically

AR Guide knowledge

Documentation

  • The primary payer's EOB or ERA
  • Current COB information for the patient
  • Payer correspondence on the order of benefits

AR Guide knowledge

Escalation

  • Eligibility: confirm the correct order of benefits with the payer
  • Client: when the patient's coverage information was not provided accurately
  • Supervisor: when payers disagree on the order of benefits

QA checkpoint

Confirm before closing

  • Verify COB order at eligibility check-in
  • Keep the primary's EOB with the account for secondary billing
  • Re-verify COB whenever the patient reports a coverage change

AR Guide knowledge

Related guides

Incorrect PayerEligibility & CoveragePatient Responsibility

Reference

Related codes

Source & review

References

AR Guide editorial research · Last reviewed Aug 15, 2026 · Reviewed. General practice guidance — not official payer or standards documentation. Payer-specific requirements must be verified with the payer.

About this guidance: Note

AR Guide knowledge is general reference content written by our team — it is not payer-specific policy and never replaces the payer’s documentation or your contract. Always confirm specifics with the payer.