I Have Two Dental Plans. Why Did Both Pay Less Than I Expected? The Coordination of Benefits Rules That Decide Who Pays First

Short answer: your two dental plans together are capped at 100 percent of the allowed expense for the procedure, not 200 percent, and that cap is usually the whole reason both plans paid less than you expected. One plan is designated primary and pays its normal benefit first. The other is secondary, and it only pays what is left unpaid up to the allowed amount, sometimes nothing at all. This is not a mistake by either insurer. It is how coordination of benefits works under the model regulation that most states have adopted, the NAIC Coordination of Benefits Model Regulation, currently in its 2013 form.

Having two plans is meant to reduce your out-of-pocket cost, and it usually does, but it was never designed to let you collect twice on the same bill. The rule that governs the order of payment and the size of the payment is written into your plan documents, and it traces back to this one model regulation. Here is how it actually works.

Step	What happens	Where it is written
1. Which plan is primary	Plan covering you as employee, member, or subscriber is primary over a plan covering you as a dependent	Section 6.D(1), NAIC Model Regulation
2. Dependent child, two parents' plans	Parent whose birthday (month and day) falls earlier in the year has the primary plan	Section 6.D(2)(a), the birthday rule
3. Primary plan pays	Pays as if the secondary plan did not exist, up to its normal benefit	Section 6.A(1)
4. Secondary plan calculates	Figures what it would have paid as primary, applies that to whatever is still unpaid	Section 7
5. Combined payment cap	Primary plus secondary payments cannot exceed 100 percent of the allowed expense for the claim	Section 7
6. Non-duplication clause, if your plan has one	Secondary plan can reduce its payment to zero if the primary plan already paid at or above what the secondary would have paid	Plan document language, not the model regulation itself

How does an insurer decide which of my two dental plans is primary?

The NAIC Coordination of Benefits Model Regulation lays out the order of benefit determination rules in Section 6.D, and plans apply them in order until one applies to your situation.

The first rule is non-dependent versus dependent. If one plan covers you directly, as an employee, member, subscriber, or policyholder, and the other covers you only because you are someone else's dependent, the plan that covers you directly is primary. This is the most common situation for adults with coverage through their own job and coverage as a spouse on a partner's plan.

The regulation carries a narrow exception for Medicare beneficiaries under Subparagraph (b), where federal Medicare secondary payer rules can flip the usual order, but that exception applies to Medicare coordination specifically, not to two private dental plans.

What is the birthday rule, exactly?

The birthday rule, at Section 6.D(2)(a) of the model regulation, decides which parent's plan is primary for a dependent child who is covered under both parents' plans. It looks only at the month and day of each parent's birthday within the calendar year, never the year itself, so the older parent does not automatically win. Whichever parent's birthday falls earlier in the calendar year has the primary plan for the child. If both parents share the exact same birthday, the plan that has covered that parent longer is primary.

The rule changes for parents who are divorced or separated. If a court decree assigns responsibility for the child's health care coverage to one parent, that parent's plan is primary, as long as the plan has actual knowledge of the decree. Without a court decree, the order runs through the custodial parent's plan first, then the custodial parent's spouse's plan, then the non-custodial parent's plan, then that parent's spouse's plan.

Why does the total still come up short even with two plans?

This is the part that surprises most people. Section 7 of the model regulation sets the actual math: the secondary plan calculates what it would have paid on the claim if it were the only plan, applies that amount to whatever the primary plan left unpaid, and can reduce its own payment so that the primary and secondary payments combined do not exceed 100 percent of the total allowable expense for the claim. Two plans do not add up to 200 percent of coverage. They add up to, at most, 100 percent of whatever the plans jointly recognize as the allowed charge for the procedure.

If your dentist's actual fee is higher than what either plan recognizes as the allowed expense, and it often is, that gap between the dentist's fee and the allowed expense is not something either plan is obligated to close, primary or secondary. That gap, not a coordination error, is frequently the real source of an unexpected balance.

What does "non-duplication of benefits" mean on my plan?

Non-duplication, sometimes labeled a carve-out clause or a maintenance of benefits clause in your plan booklet, is a specific way some secondary dental plans are written to calculate their payment. Rather than simply paying whatever is left unpaid after the primary plan, a non-duplication clause lets the secondary plan calculate what it would have paid had it been the only plan you had, then subtract the amount the primary plan already paid. If the primary plan already paid an amount equal to or greater than what the secondary plan's own fee schedule would have paid for that procedure, the secondary plan's payment on that claim is zero.

This is different from the base coordination rules in the NAIC model regulation, which govern order of payment and the 100 percent cap. Non-duplication language is written into the individual plan document itself, which is why two people with what looks like "the same kind of dual coverage" can see different outcomes: one plan's fine print includes a non-duplication clause, the other does not. If your secondary plan paid nothing on a claim, the explanation of benefits should state the reason, and a non-duplication or carve-out clause is one of the most common ones.

Should I even bother filing with my second dental plan?

Yes, every time. Section 8 of the model regulation requires plans to tell covered people, in their explanation of benefits, to file all claims with each plan they have. There is no version of coordination of benefits where filing with your secondary plan costs you money you would otherwise have kept. At worst, the secondary plan pays zero under a non-duplication clause and you are exactly where you would have been without filing. At best, there is a real balance left after the primary plan, and the secondary plan closes some or all of it.

The one place this matters procedurally: submit to your primary plan first and wait for its explanation of benefits before submitting to your secondary plan, since the secondary plan's calculation in Section 7 depends on knowing what the primary plan already paid.

What can I check if a dual-coverage dental bill looks wrong?

Three things, before assuming an error.

First, confirm which of your two plans is actually primary, using the non-dependent rule or the birthday rule above. Offices sometimes bill the wrong plan as primary, which then has to be corrected and resubmitted.

Second, ask the secondary plan's explanation of benefits to state its reason for paying less than the full remaining balance. If it cites coordination of benefits and a non-duplication or carve-out provision, that is the plan document's own language doing what it says it does, and the fix, if there is one, is in your plan booklet, not in the claim.

Third, compare the allowed expense on each explanation of benefits. If your dentist's fee is higher than the allowed expense both plans recognize, that difference sits outside coordination of benefits entirely, and is a separate conversation with your dentist's office about their fee versus your plans' allowed amounts.

A note on who we are

CheckMyDenial helps patients read and appeal insurance denials. We are related to a company that does medical-dental billing and reimbursement for patients and practices, and if you ever move from reading to having someone handle a claim for you, that relationship and any fee are disclosed before anything is paid. This page is free, it does not require anything from you, and it will stay that way.

Where this comes from

The order of benefit determination rules, the birthday rule, and the 100 percent payment cap all come from the NAIC Coordination of Benefits Model Regulation, the 2013 text published by the National Association of Insurance Commissioners, Sections 6 through 9. Most states have adopted a version of this model regulation into their own insurance code, so the mechanics on your plan should match what is described here, though your specific plan document is the final word on whether it includes a non-duplication or carve-out clause. A secondary summary of the birthday rule and order of benefit determination was checked against Aetna Federal Plans' published description of the NAIC rules. Links are listed at the end of this page. If you find something here that is out of date, tell us and we will fix it and change the date at the top.