Few things stall a claim faster than a coordination of benefits (COB) issue. When a payer isn’t sure whether a patient has other coverage, or which plan should pay first, it will often hold or deny the claim until the question is answered. The good news: most COB denials are preventable with a little verification up front.
In a recent MP Business Services webinar, billing specialists walked through why COB matters to your revenue cycle, how to verify it, and the claim scenarios most likely to come back to haunt your practice. The principles apply to both dental and medical billing.
Why COB matters
It prevents claim delays. Payers often delay or refuse payment until they’ve confirmed whether other insurance exists. Some will pend the claim, mail a COB questionnaire to the subscriber, and wait for a response before processing. If the patient doesn’t respond within the required timeframe, your claim gets denied.
It sets the payment order. COB establishes which plan is primary, which is secondary, and, for patients with three coverages, which is tertiary. Billing in the wrong order means denials and rework.
It avoids overpayments. When COB hasn’t been completed and a patient has two active plans, both may pay as primary. Payers generally won’t correct or recoup those overpayments until COB is resolved, which can leave your practice holding funds that will eventually be taken back.
It isn’t a one-time task. Many payers require COB to be updated every year, especially for dependents and covered spouses. These requests don’t always arrive in January; some payers send them during their enrollment period and stop processing claims until the member responds.
How to verify COB
There are three main ways to uncover COB information, and it’s worth using whichever one you’re already in.
Payer portals. More payers now display COB details online. Look for tabs labeled “Additional Coverage,” “Other Payer Information,” or “Coordination of Benefits.” Portals may also show when COB is next due and, if another plan is primary, the details of that plan.
Phone calls. Representatives rarely volunteer COB information, so ask directly: “Is this plan primary or secondary?” and “Is there other coverage on file?” Ask about the patient you’re calling on and any other family members you see, since COB is tracked for each member individually.
Benefit and eligibility faxes. When a fax comes back, review it for COB details rather than just the coverage summary.
One note on terminology: many state Medicaid programs list other primary coverage as third-party liability (TPL). If you’re checking a Medicaid portal, TPL is where you’ll find a patient’s other insurance.
Claim scenarios that come back to haunt
Newborns. COB is almost always required before a newborn’s claims are processed. A newborn may also have automatic coverage for 30, 45, or 60 days under a parent’s policy, and the parents may not know it. They often provide only the plan they added the baby to. Get copies of both parents’ insurance cards, verify newborn coverage on both policies, and make sure COB is completed on both. Otherwise, a payer may recoup months of newborn payments a year or more later.
The birthday rule. When a child is covered by both parents, the parent whose birthday falls earlier in the calendar year is generally primary. Only the month and day count; the birth year/parents’ age doesn’t matter. Custody arrangements or court orders can change this order, so confirm with the payer when they apply.
Every covered member needs their own COB. A subscriber can complete COB for everyone on the plan, and it must be done for each member. Patients often say they’ve completed COB without realizing they only did it for themselves, so claims for other members keep denying.
One person, two employer plans. When someone has coverage through two employers, the plan they’ve held longer is generally primary. Similarly, a person’s own employer coverage is typically primary to coverage they hold as a spouse or dependent on someone else’s plan. Payers make the final determination in unusual cases, so verify.
Reprocessing after COB is updated. When you ask a patient to update COB, also ask them to request that their denied claims be reprocessed. Some payers say they reprocess automatically, but it doesn’t always happen, and others require a separate request.
Dollar thresholds. Some payers will pay claims under a certain amount even when COB is overdue, then deny larger claims until it’s completed. This can make it look like the payer is processing claims inconsistently. If small claims pay and larger ones deny, check COB status.
A dental-specific note. Federal employees with a Blue Cross Blue Shield medical plan through the federal program may have limited dental benefits built into that medical plan, typically covering exams, cleanings, and fluoride. That coverage is generally primary to the patient’s separate dental plan, so bill it first.
Where Medicare and Medicaid fit
Medicaid pays last. When a patient has any other credible coverage, including commercial insurance, Medicaid is the payer of last resort. This applies to dental as well as medical.
Medicare depends on employment. For patients still working and covered by an employer plan, that employer coverage is often primary and Medicare secondary. For retirees, Medicare is generally primary and any retiree group coverage becomes secondary, sometimes functioning as a supplement. Exceptions exist, including for former federal employees, so check the Medicare portal, which reflects these changes, and confirm the patient has completed COB on both plans.
Medicare Advantage replaces Original Medicare. If a patient has a Medicare managed care plan, bill that plan as primary, not regular Medicare.
Dual Medicare and Medicaid patients. For services Medicare doesn’t cover, bill Medicare first to obtain a denial, then bill Medicaid with that denial. Some state Medicaid programs accept claims directly for services they know Medicare excludes, so check your state’s rules.
Non-Medicare providers. If your practice isn’t enrolled with Medicare, you can’t bill Medicare, even for a denial. In that case, the patient’s other coverage is billed as primary. Check payer guidance for your specific situation.
Key takeaways
- Missing or outdated COB delays or denies claims and can leave you holding overpayments that will be recouped later.
- Many payers require COB annually, often outside the calendar-year cycle.
- Verify COB through portals, phone calls, and eligibility faxes; Medicaid may list other coverage as third-party liability (TPL).
- For newborns, collect both parents’ cards, verify both policies, and have them complete COB for both.
- Under the birthday rule, the parent with the earlier month and day is generally primary.
- COB must be completed for each covered member, not just the subscriber.
- Medicaid always pays last; Medicare’s position depends largely on whether the patient is still working.
Action items
- Confirm primary and secondary coverage before any claim goes out the door.
- Add COB questions to every payer call and ask about each family member you see under that plan while you’re on the line.
- Check portals for COB due dates and other-coverage details during routine eligibility checks.
- At a newborn’s first visit, ask parents to complete COB with both payers and request copies of both insurance cards.
- When asking patients to update COB, also ask them to request that denied claims be reprocessed.
- If small claims pay while larger ones deny, check COB status first.
COB takes a few extra minutes up front, but it’s far less work than chasing denials and refunding overpayments later. If your practice needs help with COB, denials, or other insurance billing challenges, reach out to MP Business Services at [email protected].
