Coordination of Benefits Denials: What They Are and How to Resolve Them

You submit a clean claim. Two weeks later, it comes back denied with a CO-22 or OA-23, and the payer says the patient has another insurance plan you didn't know about. Coordination of benefits denials are one of the most repetitive, time-draining denial categories in behavioral health billing. They sit in A/R, they often require the patient to call their insurer, and if you wait too long, timely filing runs out. Here's what these denials mean, why they show up so often in mental health practices, and a practical workflow to resolve them.

What Coordination of Benefits Denials Actually Mean

Coordination of benefits (COB) is the process insurers use to decide who pays first when a patient has more than one plan.[1] When two payers disagree about who's primary, or when the payer's records don't match what you have on file, your claim bounces back as a COB denial.

The two codes you'll see most often are different problems with different fixes.

CO-22 means "this care may be covered by another payer per coordination of benefits."[2] The payer thinks someone else is primary and won't process the claim until that's sorted out.

OA-23 means "the impact of prior payor(s) adjudication including payments and/or adjustments."[3] The primary already paid, and this is the secondary payer showing you the math. It's not really a denial in the same sense as CO-22, but staff often treat it like one and resubmit the claim, which just creates more work.

One concept ties both of them together: payer of last resort. Medicaid is always last in line, no matter what other coverage exists.[4] EAP plans are often first when the visit qualifies as an EAP-covered service. If your billing system has these in the wrong order, every claim will denial-loop until you fix the sequence.

Why COB Denials Are So Common in Behavioral Health

A few things make behavioral health especially prone to these denials.

EAP confusion sits at the top of the list. Many therapy patients have an Employee Assistance Program through their employer that covers a set number of sessions, and EAP usually has to be billed before the medical insurance kicks in. Staff don't always know the patient has EAP, or they bill medical first out of habit.

Medicare and Medicaid dual eligibility shows up constantly in community-based programs like ARMHS, CTSS, and EIDBI. The order depends on which other coverage exists, but Medicaid is always last, and getting that wrong creates a CO-22 every time.

Patients update their insurance with HR but never call their payer's COB department. So the payer's system still shows last year's spouse-plan-plus-employer-plan setup, even though the patient dropped one of them months ago. The first you'll hear about it is when the claim denies.

Family plans bring the "birthday rule" surprise. For a child covered by both parents, the parent whose birthday falls earlier in the calendar year is primary.[5] Most parents don't know this, and it routinely catches solo therapists who see kids.

January is the worst month. Every plan change, every new job, every Medicare transition creates a wave of behavioral health claim denials tied to coordination of benefits.

The Step-by-Step Resolution Workflow

When a COB denial lands in your queue, work it in this order.

1. Read the EOB carefully. Does it say "bill primary first" (CO-22) or "primary already paid, here's our portion" (OA-23)? The fix is different for each.
2. Verify current coverage in the payer portal or by phone. Confirm what the payer has on file for primary and secondary. If their records are stale, you've found your problem.
3. If COB is out of date, contact the patient. Give them the exact phone number for their insurer's COB line and a simple script: "I need to update my coordination of benefits. My primary is X and my secondary is Y." Patients can't fix what they don't understand, so spell it out for them.
4. For OA-23, attach the primary EOB and submit to the secondary. Don't resubmit, supplement. The secondary needs to see what the primary paid before it'll process your claim.
5. Document the call reference number and set a follow-up reminder for 7-10 business days. Without that reminder, COB denials sit in A/R until they age out.

When to appeal versus correct: if the payer's COB records are wrong and you have proof, an appeal with documentation is usually the right path. If you billed the wrong payer order, a corrected claim is faster than an appeal.

Watch the clock. Most commercial payers give you 90 to 180 days from the date of service for timely filing.[6] COB denials can eat 30 to 60 days while you're chasing the patient to call their insurer, so a denial that arrives at day 45 doesn't leave much runway.

Preventing COB Denials Before They Happen

The best fix for COB denials is not getting them in the first place. A few habits cut the volume sharply.

Verify eligibility for every new client and re-verify in January and after any coverage change. The payer portal will usually show you the current COB status if you ask the right question.

Ask intake questions that surface dual coverage. A single line on the intake form helps: "Do you have any other insurance, including through a spouse, EAP, or Medicare/Medicaid?" Most patients will answer honestly if you ask directly.

Train front-desk and intake staff to spot EAP coverage and route it correctly. It's the most common miss, and a five-minute training pays for itself many times over.

Build a monthly A/R aging report review that surfaces COB denials before they hit timely filing limits. The denials you catch at 45 days are recoverable. The ones you catch at 120 days usually aren't.

Keep a simple tracker so patterns by payer become visible. If your denial rate for CO-22 is concentrated with one or two payers, that's where to tighten verification first.

Final Thoughts

Coordination of benefits denials aren't usually a coding problem. They're an information problem. The patient has coverage you didn't know about, or the payer has records the patient never updated. Either way, the fix involves a phone call, the right documentation, and a clock that's ticking against timely filing.

That's where a relational approach to billing matters. BreezyBilling assigns a dedicated coordinator who verifies benefits before the first session, catches COB issues upstream, and follows up with patients to get coverage updated, so coordination of benefits denials don't sit in A/R for months. If COB denials are stacking up at your practice, we'd be glad to talk through how we can help. Reach out anytime for a conversation.

Sources

1. Coordination of Benefits Overview. Centers for Medicare and Medicaid Services, 2024.
2. Claim Adjustment Reason Codes. X12, 2024.
3. Denial Code OA-23: Description, Causes and Fixes. iMedClaims, 2024.
4. Who Pays First. Medicare.gov, 2024.
5. Coordination of Benefits. American Academy of Pediatrics, 2024.
6. CO-22 Denial Code: Coordination of Benefits Issues. FC Billing, 2024.