A claim comes back with reason code 22, this care may be covered by another payer per coordination of benefits, and nothing moves until somebody fills out a form. How to fill out coordination of benefits comes down to three separate documents with three different owners: the carrier questionnaire that only the subscriber can answer, the Other Coverage block in items 4 through 11 of the ADA Dental Claim Form, and your own intake record of the second plan. Most stalled claims are a mix-up about which one is missing.
Which document you are actually being asked to fill out
When a payer, a patient or a coworker says coordination of benefits form, they could mean any of three things. Sorting that out first saves a week.
The carrier questionnaire. Sometimes called an other coverage questionnaire or a COB update form. The carrier mails it to the subscriber's address on file or posts it in the member portal, and it asks the member to attest to every other health and dental plan in the household. Your office cannot complete this. Carriers will not accept it from a provider, because it is an attestation by the member. Many carriers refresh it on a cycle, so a long-standing patient can suddenly generate a hold on a routine prophy claim with nothing else changed.
The Other Coverage block on the claim. Items 4 through 11 of the ADA Dental Claim Form. This one is yours, it is filled out on every claim for a two-plan patient, and it is where most preventable rejections come from.
Your own intake capture. The registration form field where the patient lists a second plan. It has no standing with any carrier, but it is the only reason you know to ask the other two questions before the visit rather than after the denial.
If you want the underlying mechanics of which plan pays first and what the second one owes, our explainer on coordination of benefits in dental insurance covers primary versus secondary in detail. This article is about the paperwork.
How do I set up coordination of benefits?
Setting it up means telling each carrier that the other one exists. It is a member transaction, and the practice's job is to make it happen fast and to document that it did.
- Get both cards in front of you at check-in. Photograph or scan both sides of each. You need the carrier name, the subscriber ID exactly as printed including any alpha prefix, the group number, the subscriber's name and date of birth, the relationship of the patient to that subscriber, and the effective date.
- The subscriber calls or updates the portal for each plan. The member services number on the back of the card, or the section usually labeled other coverage, other insurance, or update coverage information. A dependent cannot usually do this for a plan they do not subscribe to, which is why the working parent often has to make the call.
- Do it for both carriers. This is the step that gets skipped. Updating only the plan that denied leaves the second carrier with the same incomplete file, and the next claim denies the same way.
- Capture a reference number and the date. Ask how long the update takes to post. Turnaround is quoted anywhere from same day to about ten business days depending on the carrier, so ask rather than assume.
- Ask whether they will reprocess or need a corrected claim. Some carriers reprocess the held claim automatically once coordination is on file. Others want a new submission. The answer changes what your follow-up looks like, so get it on the note.
- Watch timely filing. A coordination hold does not usually pause the filing clock. Confirm the deadline in your participating provider agreement and with the payer, and track the claim against that date, not against the carrier's promise to reprocess.
One protection worth knowing: under the model coordination provision, a plan may not cut its benefits simply because another plan exists that the patient could have enrolled in and did not. Having a second plan available is not the same as having it.
Filling out the Other Coverage block, items 4 through 11
This is the part your office actually completes. On the current ADA Dental Claim Form, the Other Coverage block sits at the top of the form, immediately under the carrier you are billing.
| Item | What it asks | What goes in it |
|---|---|---|
| 4 | Is the other coverage dental, medical, or neither | Mark what applies. If the patient has both, items 5 through 11 describe the dental plan only |
| 5 | Name of the policyholder or subscriber on the other plan | The subscriber's name, which is not the patient's name when the patient is a dependent |
| 6 | That subscriber's date of birth | MM/DD/CCYY, with the four digit year |
| 7 | That subscriber's sex or gender | Use only the values the form offers |
| 8 | Policyholder or subscriber ID assigned by the other plan | Copy it from the card exactly, including any letter prefix and without spaces you invented |
| 9 | Plan or group number of the other plan | The employer group number, not your provider number and not the plan name |
| 10 | Patient's relationship to the person named in item 5 | Self, spouse, dependent child, or other |
| 11 | The other carrier's name and mailing address | Payer name and claims address for the other plan |
Four rules govern the block, and three of them are the reason secondary claims reject.
The block always describes the other plan, not the one you are billing. On the claim you send to the primary, items 4 through 11 describe the secondary. On the claim you send to the secondary, the same items describe the primary. Items 12 through 17 always describe the plan currently being billed. Filling the block with the billed plan's own details is a top cause of rejection, and it is easy to do when software carries fields forward between the two submissions.
Item 4 is not decoration. Marking that the other coverage is medical rather than dental changes how the claim is read. Trauma repairs, biopsies, and certain surgical extractions can be medical-first cases, and pediatric dental benefits embedded in a medical plan are a genuine coordination scenario rather than an edge case.
The primary's payment detail has to ride along with the secondary claim. Electronically, that is the adjudication data in the claim's coordination segments. On paper, it is a legible copy of the primary EOB. Some payers still insist on paper for secondary claims. Confirm per payer instead of assuming your clearinghouse handles all of them the same way.
Never change the codes or the fees between the two claims. Same CDT codes, same dates of service, same submitted fees on both. Rebilling the secondary at the leftover balance is common and it costs money, because the second plan calculates from the submitted and allowed amounts, not from what you say is outstanding. Consistent coding across both submissions is also one of the quiet arguments for automated dental coding, since the second claim inherits whatever the first one got wrong.
Can you provide an example of coordination of benefits?
Here is the arithmetic on a single crown, D2740, crown, porcelain/ceramic. These numbers are illustrative, chosen to be round rather than typical.
The office fee is 1,300 dollars. The primary plan allows 900 and covers major services at 50 percent with the deductible already met. The secondary plan allows 850 and also covers major at 50 percent. Both plans calculate against their own fee schedule, which is why the two EOBs rarely show the same numbers.
| Step | Standard coordination | Non-duplication |
|---|---|---|
| Primary allowed amount | 900 | 900 |
| Contractual write off, 1,300 minus 900 | 400 | 400 |
| Primary pays, 50 percent of 900 | 450 | 450 |
| Balance after primary | 450 | 450 |
| What the secondary would have paid as primary, 50 percent of 850 | 425 | 425 |
| Secondary's calculation | Lesser of 425 or the 450 still owed | 425 minus the 450 the primary already paid |
| Secondary pays | 425 | 0 |
| Patient owes | 25 | 450 |
Same patient, same two plans, same procedure, and a 425 dollar swing in what you collect at the front desk. The method lives in the secondary plan's contract, not in the carrier's brand, so it has to be verified plan by plan. That is precisely the kind of question a routine eligibility response will not answer, and a reason two-plan patients belong in a deep verification of benefits rather than a quick active-or-not check.
Two details that follow from the example are worth writing on the account note. First, when the secondary pays nothing, that is coordination working, not a denial to appeal. Second, a secondary plan is generally expected to credit its own deductible with the amounts it would have credited if there had been no other coverage, so do not assume the patient's secondary deductible is still fully outstanding at the next visit. Ask.
On a large case, run this arithmetic before treatment rather than after. A pre-determination of benefits sent to the primary, with the secondary identified in items 4 through 11, gives you the primary's allowed amount in writing and turns the estimate from a guess into subtraction.
What are the 7 rules of COB?
The commonly quoted seven rules are the order of benefit determination rules from the NAIC Coordination of Benefits Model Regulation. The model actually lists six numbered rules, and the second one splits into two branches depending on the parents' situation, which is how the count becomes seven. They are applied in sequence, and the first rule that resolves the question decides the order.
| Order | Rule | Which plan is primary |
|---|---|---|
| 1 | Non-dependent or dependent | The plan covering the person as an employee, member, subscriber, policyholder or retiree pays before the plan covering that same person as a dependent |
| 2a | Dependent child, parents married or living together | The birthday rule: the parent whose birthday falls earlier in the calendar year. Month and day only, never the birth year. If both parents share a birthday, the plan that has covered that parent longer is primary |
| 2b | Dependent child, parents divorced, separated or not living together | A court decree assigning responsibility controls, if the plan has actual knowledge of it. With no decree: the custodial parent, then that parent's spouse, then the non-custodial parent, then that parent's spouse |
| 3 | Active employee or retired or laid-off employee | Coverage based on active employment pays before retiree or laid-off coverage |
| 4 | COBRA or state continuation | Coverage as an active employee, member or retiree pays before COBRA or state continuation coverage |
| 5 | Longer or shorter length of coverage | The plan that has covered the person longer is primary |
| 6 | Nothing above resolves it | The plans share the allowable expense equally |
Three qualifications matter as of this writing. States adopt the model regulation with their own variations, so the binding text is your state's rule, available from your state insurance department. Self-funded employer plans governed by ERISA are not subject to state insurance regulation and set their coordination order in the plan document, which often tracks the model but does not have to. And Medicare follows its own secondary payer rules, published by CMS, which can reverse rule 1 in certain situations involving a Medicare beneficiary who is also covered as the dependent of an active employee.
There is also a floor the rules protect. However the order comes out, the plans together are not meant to pay more than 100 percent of the total allowable expense. Coordination exists to prevent duplicate payment, not to shrink the total below what one plan alone would have paid.
What are the common issues with coordination of benefits?
Almost none of them are billing errors. They are tracking failures.
| What you see | Usual cause | What clears it |
|---|---|---|
| Reason code 22 on a first-time claim | The carrier's file shows other coverage the patient never mentioned, sometimes an old plan that ended | Call the carrier to learn what coverage they show, then have the subscriber confirm or terminate it with them directly |
| Denied again after the patient says they updated it | Only one of the two carriers was told | Both carriers need the update, with a reference number from each |
| Secondary pays zero | Non-duplication, and the primary already paid at or above the secondary's calculated benefit | Nothing to appeal. Read the reason code, bill the patient the residual, and note the method on the plan record |
| Secondary rejects for missing primary payment information | The EOB was not attached, or the coordination fields on the electronic claim were incomplete | Resubmit with the primary's full adjudication detail, per that payer's stated format |
| Both plans deny as secondary | Neither carrier has the order established | Determine the order with the rules above, then have the subscriber confirm it with both carriers |
| Allowed amount lower than either plan quoted | One plan applied an alternate benefit to the procedure | Compare against the plan's provisions. See our guide to the alternate benefit provision |
| Claim ages past timely filing on a coordination hold | The hold was treated as a pause on the clock | Track held claims on a dated worklist with a follow-up date set well inside the filing deadline |
| Annual questionnaire never returned | Mailed to a stale address, or opened and ignored | Point the patient at the member portal, which is usually faster than the mailed form |
A coordination hold is silent: no money to post, no balance to chase, no unhappy patient calling, so the claim sits in a status nobody reads until the filing deadline turns it into a write-off. Whatever your system, held coordination claims need a dated worklist with a human owner, and every one of them needs a follow-up date that leaves room to resubmit. Curo flags coordination reason codes as the remittances arrive and keeps each held claim on a countdown against its filing deadline, which is the same discipline as any other denial management queue, just applied to a status that never announces itself.
The cheapest fix in this entire article costs nothing and happens at registration. Stop asking patients whether they have other insurance, because they hear it as a question about duplicate dental plans and answer no. Ask instead whether anyone else in the household carries coverage that includes them: a spouse's plan, a parent's plan, retiree coverage, a medical plan with a dental or pediatric dental component. The yes rate on the second question is noticeably higher, and every yes you catch at the desk is a claim that never sits on a coordination hold at all.