10 standard Coordination of Benefits rules for dental insurance billing [Free guide]

Understanding and applying Coordination of Benefits rules is crucial for claim acceptance and prompt reimbursement. You can have fewer claim appeals and more consistent cash flow when your team knows how to navigate these 10 Coordination of Benefits rules. 

The subject of Coordination of Benefits (COB) is a doozy for most dental professionals — more paperwork leads to more problems.

When a patient shows up to your dental business covered by more than one insurance plan, submitting their claims can get complicated. And it can be challenging to remember every COB rule when each patient has a different circumstance to consider. 

Fortunately, here at DCS, our pool of dental billing experts has extensive knowledge on tricky subjects like Coordination of Benefits. At DCS, we pride ourselves on what we call the DCS Knowledge Network, and their knowledge is packed in this article that covers 10 standard Coordination of Benefits rules every dental professional should know.

Make sure you download the free PDF that lists each of these 10 COB rules. Keep this handy at your desk to refer to when you’re managing patients covered by more than one insurance plan. Just fill out the form below, and you’ll receive the list in your inbox within minutes. 

Key takeaways about Coordination of Benefits rules: 

• Accepting secondary insurance will widen your pool of patients
• COB doesn’t have to be scary
• Your claims revenue and cash flow depend on applying COB rules correctly
• When in doubt, your team can always call insurance companies and ask for clarification

What is Coordination of Benefits (COB) for dental practices?

Coordination of benefits defines the sequence insurance claims are filed for patients covered by multiple insurance plans. One plan will be the primary insurance, while the other is secondary, and occasionally there are third (tertiary) and fourth (quaternary) plans. 

Related: DCS Dictionary: Dental Insurance Billing Terms

Why is it important to know Coordination of Benefits rules?

It’s critical for your dental team to know the rules of COB because everyone wins when you accept multiple insurance plans from patients. It increases the pool of patients and revenue that your practice can bring in, and more patients can benefit from your services. 

And when your team applies these COB rules correctly, they’ll avoid claim mistakes that lead to denials, appeals, and payment delays.

There are plenty of rules and conditions when it comes to COB, which is what makes them hard to work with. To make them simpler, we’ll explain 10 standard rules of COB you can keep in your back pocket for when you’re filing multiple insurance claims for a single treatment. 

These rules will help you determine which of the patient’s insurance plans is the primary, depending on the situations described.

10 Coordination of Benefits rules you need to know

1. Employee/member/subscriber vs dependent

This COB rule applies when a patient is subscribed to multiple insurance plans — one as a member, and the other as a dependent. In this case, the plan where they are subscribed as a member would be the primary insurance. The plan where they are a dependent would be the secondary insurance. 

For example, Parker just got their first full-time job, and it includes insurance benefits, yet they’re still officially a dependent on their parent’s insurance plan. In this case, their employer-based plan is the primary insurance, and their parent’s plan is the secondary insurance.

2. Actively employed vs retired/laid off/COBRA

This COB rule applies to patients who have recently become unemployed and have insurance through their former employer and some other source. Assuming their benefits are still active, the plan they were covered by before they retired or were laid off would be the primary plan. The coverage they now have as someone who is inactively employed would be their secondary insurance. 

For example, Taylor has been laid off, and their former job’s insurance benefits are still active for another month or two. But before that plan will terminate, they enrolled and are eligible with another insurance plan. Their former employer’s plan is their primary coverage, and their new plan is their secondary insurance.

This can happen when a patient takes advantage of COBRA, or the Consolidated Omnibus Budget Reconciliation Act. This is a federal law that allows the insured to extend their insurance coverage by paying out-of-pocket premiums after voluntary or involuntary job loss or other major life event.

3. One subscriber with two jobs

This is an easy one! This COB rule applies when a patient has two jobs, and they are enrolled in benefits packages at both jobs. Whichever plan they enrolled in first will be the primary insurance. Then, the insurance plan they enrolled in later with their second job would be the secondary insurance.

For example, Jordan started working at Acme, Inc. back in 2019, then got a second job at Big Corp in 2023. Acme would be their primary insurance, and Big Corp would be their secondary insurance.

Read More: 5 dental claim submission mistakes that will cost you time and money

4. Spousal coverage

This COB rule applies to spouses who have insurance plans from their respective jobs, but are also enrolled in the other’s health plan. The insurance plan through their own job would be their primary insurance, while their spouse’s plan would be their secondary insurance. 

For example, Pat and Alex are married and both enrolled in both of their employer’s health plans. When Pat visits your office for a procedure, their employer’s plan is their primary insurance, and Alex’s plan is their secondary insurance. 

5. Dependent children of parents who are married (aka The Birthday Rule)

This COB rule applies when married parents have their own insurance plans, and both parents have added their child to their insurance. The child’s primary insurance is the plan covering the parent whose birthday occurs earliest in the year 

To be clear: this does not mean the parent who is the oldest, it means the parent whose birthday comes first in the calendar year would have the primary coverage. 

For example, Pat and Alex have a child, Casey. Casey is enrolled in both parents’ insurance plans. Pat’s birthday is March 26, 1987, and Alex’s birthday is June 11, 1985. Pat’s insurance would be primary because their birthday falls first in the calendar year. Alex’s insurance is secondary because their birthday is later in the year; it doesn’t matter that they were born first.

On the rare occurrence that both parents are born on the same day, the primary insurance holder would be the parent who has been covered by their insurance plan the longest.

For example, Dylan and Avery were both born on August 3, 1982. Dylan has been with their insurance plan since January 1, 2017, and Avery’s plan started on March 15, 2015. For their child, Bailey, Avery’s plan would be the primary insurance, and Dylan’s plan would be secondary.

Related: What is dental billing? An understanding of how dental billing works

6. Dependent children of parents who are separated or divorced

This COB rule for separated or divorced parents is similar to #5 Dependents of parents who are married, but is listed separately because it includes special conditions.

If the child’s parents are divorced or separated, the parents have joint custody, and the child is a dependent on both parents' insurance plans, The Birthday Rule mentioned above applies: Whichever parent was born earliest in the year will have the child’s primary insurance.

For example, as with COB Rule #5, Pat and Alex are separated and have a child, Casey. Casey is enrolled in both parents’ insurance plans. Pat’s birthday is March 26, 1987, and Alex’s birthday is June 11, 1985. Pat’s insurance would be primary because their birthday falls first in the calendar year. Alex’s insurance is secondary because their birthday falls later in the year; it doesn’t matter that they were born first.

If the parents do not have joint custody, but the child is still covered by both parents’ insurance plans, the child’s primary insurance will be the parent who has custody according to a court of law.

For example, if the courts were to give Alex full custody of Casey in their divorce from Pat, then Alex’s insurance would become the primary, as Pat no longer has custody of the child. 

It’s worth noting that divorce/custody issues can lead to additional delays in deciding COB. Parents may need to write up “Parenting Plans” and file them with the courts before the insurance carriers can agree on COB. It’s not extremely common, but it does happen.

7. Dependent children who also have coverage under a spouse’s dental plan

This COB rule applies to patients who have married and are on their spouse’s insurance plan, but they are also on their parent’s insurance. The primary insurance would be whichever plan the patient has been a dependent on the longest.

For example, Campbell was added to their parent’s insurance on March 3, 2024, but started on their spouse’s insurance on June 6, 2022. Campbell’s spouse’s plan is their primary insurance because they joined that plan first, and their parent’s insurance is secondary.

8. Medical plan vs. dental plan

This COB rule applies if a patient has both medical and dental coverage. If the insurance for a procedure performed by a doctor is available under the patient’s dental AND medical plan, the medical plan will be the primary insurance. This rule applies typically when the procedure is oral surgery, trauma-related, or pathology.

It’s also dependent on whom the provider is in-network with. If there are medical and dental insurance on file, and the medical is IN network, then medical must be billed first (if the services are billable to medical, because not all are).

For example, Blair has both dental and medical insurance through their employer. Blair had a softball mishap that required oral surgery, and for that procedure, their medical plan would be the primary insurance. A few months earlier, when Blair had a standard dental cleaning, their dental insurance was the primary.

It’s also important to know if there are medical and dental insurance on file, and the medical is OUT of network, then dental can be billed first.

Another example: Let’s say Pat needs wisdom teeth extracted under sedation, so they go to an oral surgeon. Tooth extractions are services that can be billed to both medical and dental. They have medical and dental insurance, but the medical insurance is out of network with the provider. In this case, dental is billed first. Once the dental is paid, it can then be sent to medical.

Read more: Medical claims vs dental claims in dental billing

9. Medicaid

This COB rule applies when a patient is insured by Medicaid, the state-funded plan for lower income and disabled people. It can have medical, dental, and sometimes vision coverage.  

Sometimes people who are enrolled with Medicaid also have private insurance. If the patient is covered by Medicaid, their private dental plan is always the primary, with the government program as the secondary or last resort coverage.

For example, Carter has had federally funded Medicaid insurance since 2017. They got a job at Widgets, Inc. in 2024 that also includes health insurance, but they still qualify for Medicaid.

This resembles COB Rule #3: One subscriber with two jobs, where the plan they’ve held the longest is the primary insurer, but it makes a difference that one of the plans is government-supported. Carter’s new employer’s plan would be their primary insurance, even though they’ve had the Medicaid longer. 

10. Medicare vs. retiree plan

This COB rule applies to patients covered by both Medicare and a retiree’s insurance plan. Typically, Medicare is only available to a patient after they reach 65 years old, but they may be eligible earlier under specific medical conditions.

In that case, until they reach 65 years old, their retiree plan is the primary insurance, and Medicare is their secondary insurance. After the patient turns 65 years old, Medicare would be their primary insurer and their retiree plan would be secondary. 

For example, Drew qualifies for Medicare at age 60 because they’ve been diagnosed with Amyotrophic lateral sclerosis (ALS), aka Lou Gehrig's disease. Now age 64, Drew’s retiree plan would be their primary insurance. Next year, after they turn 65, Medicare will be their primary insurance and their retiree plan would be their secondary.

If a patient is on their spouse’s insurance plan in addition to their own retiree plan, and  Medicare, then their spouse’s plan would be their primary insurance (even though they are a dependent), Medicare would be secondary, and their own retiree plan would be tertiary.

Download this list of 10 Coordination of Benefits Rules for Dentists

This list might seem like a lot. But guess what? You don’t have to memorize it! Get the 1-page 10 Coordination of Benefits Rules for Dentists straight to your inbox to download, print, save, and share by filling out the form below. 

Avoid claim denials and payment delays when you use this handy list to properly coordinate your patients’ benefits. 

Coordinate your dental patients’ benefits confidently when the DCS Knowledge Network is on your team

Let’s recap the significance of including Coordination of Benefits in your dental business: 

• If you don’t already, you should accept secondary insurance to increase your patient pool and revenue
• There are nearly a dozen of COB rules to cover various multi-insurer situations
• Don’t let COB rules stress out your team—this list will help them confidently coordinate your patients’ benefits
• If they’re still stressed and confused over COB rules, turn to experts like ours at the DCS Knowledge Network

Remember, you can fill out the form above to get this list of COB rules as a brief PDF that you can download, print, and share.

And if you still need assistance when it comes to COB or insurance billing in general, the DCS Knowledge Network has your back. DCS offers end-to-end revenue cycle management solutions, including our insurance billing solutions. We’ll help your team navigate complicated dental insurance rules, and get your claims reimbursed promptly. 

Coordinate benefits confidently with our experts on your side: Book a free 30-minute consultation with DCS today.