When two group health or dental plans cover the same person, usually because both partners have workplace benefits, coordination of benefits (COB) decides which plan pays first and how much the second plan adds. You claim from the first plan, then send the unpaid part to the second. When both plans cover the expense, the two together can often pay up to the full eligible amount, but never more than 100% of it.
In Canada the order is set by the Canadian Life and Health Insurance Association’s Guideline G4, Coordination of Benefits, which the association’s member insurers are expected to adopt. This page walks through its rules: who pays first for you, a spouse and children, how the second plan works out its payment, and where the limits are. It is one of the employer benefits guides in the workplace rights and employee benefits hub.
How Coordination of Benefits Works: Step by Step
| Step | What happens |
|---|---|
| 1. Work out the first payer | Your own plan pays first for your claims; the birthday rule decides for children |
| 2. Claim from the first plan | Electronically at the provider, or on paper |
| 3. Get the Explanation of Benefits (EOB) | The first plan’s statement of what it paid and why |
| 4. Claim from the second plan | Send the claim with the first plan’s EOB (or the electronic claim details) |
| 5. The second plan pays its share | Up to the unpaid balance, limited by what it would have paid on its own |
| 6. Neither plan overpays | The combined payment can’t exceed 100% of the eligible expense |
If the first plan pays the whole eligible amount, a claim to the second plan isn’t needed, unless you want the expense to count toward that plan’s deductible or maximums.
Which Plan Pays First
| Whose claim | First payer | Second payer |
|---|---|---|
| Your own | Your own group plan | The plan that covers you as a dependant (your spouse’s) |
| Your spouse’s | Your spouse’s own group plan | Your plan, which covers them as a dependant |
| You have two plans of your own | The plan where you’re an active full-time employee, then part-time, then retiree | If the status is the same, the plan that has been in effect longest pays first |
| A student with a student health or dental plan | The student plan | A parent’s plan that covers the student as a dependant |
| A dependent child (joint custody or parents together) | The plan of the parent with the earlier birthday (month and day) in the calendar year | The other parent’s plan |
| A dependent child (single custody) | The custodial parent’s plan, then that parent’s spouse’s plan | Then the non-custodial parent’s plan, then that parent’s spouse’s plan |
A few other rules sit around this order:
- A plan with no COB provision pays first, ahead of a plan that has one.
- Government plans pay first. Coverage under a federal, provincial or territorial health plan or program comes before a private group plan, except where the legislation or program says otherwise.
- Health spending accounts usually pay last. Trade press reports that coverage under all group plans is considered before a health care spending account, which falls outside the insurers’ coordination guideline, so an HSA usually picks up what both plans leave unpaid.
- Individual plans may pay second to a group plan, depending on the individual plan’s terms.
- Dental accidents go first to a health plan that covers dental accidents, then to the dental plans.
The Birthday Rule for Children
For a child covered by both parents’ plans, the plan of the parent whose birthday comes earlier in the calendar year pays first. Only the month and day count, not the year of birth or which parent is older. If both parents share a birthday, the order follows the alphabetical order of the parents’ first names.
| Parent A’s birthday | Parent B’s birthday | First payer for the children |
|---|---|---|
| March 3 | September 14 | Parent A’s plan |
| October 7 | February 22 | Parent B’s plan |
| April 12 | April 27 | Parent A’s plan |
| June 5, 1982 (first name Sam) | June 5, 1985 (first name Alex) | Alex’s plan (same birthday, so alphabetical by first name) |
When parents are separated and one has single custody, the birthday rule doesn’t apply: the custodial parent’s plan pays first, as in the table above. The guideline lets the order be changed when it isn’t working, for example when one parent can’t recover payment from the other parent’s plan, if the second plan’s sponsor asks in writing and the insurer agrees.
How the Second Plan Calculates Its Payment
The first plan pays as if no other coverage existed. The second plan pays, for each item on the claim, the lesser of:
- what it would have paid if it had been the first payer, or
- 100% of the eligible expense minus what the first plan paid.
A dental filling, both plans covering 80%. The eligible fee is $300; each plan covers 80% of it.
| Plan | How it’s worked out | Pays |
|---|---|---|
| First plan | 80% of $300 | $240 |
| Second plan | Lesser of $240 (its own 80%) and the $60 left | $60 |
| Total | $300 |
The two plans together pay the whole eligible fee.
A crown when the second plan’s maximum is nearly used up. The eligible fee is $1,200. Both plans cover 50% of major work, but the second plan has only $400 left of its annual maximum.
| Plan | How it’s worked out | Pays |
|---|---|---|
| First plan | 50% of $1,200 | $600 |
| Second plan | Its own share would be $600, capped by the $400 left of its maximum; $600 is unpaid | $400 |
| Total | $1,000 |
You pay the remaining $200.
A visit or expense that a plan pays only in part still counts as a visit, and its cost counts toward that plan’s maximums. That matters for plans that limit the number of visits (physiotherapy, massage) or set dollar caps.
Limits Both Plans Share
| Principle | How it works |
|---|---|
| 100% ceiling | The combined payment for an item can’t exceed 100% of the eligible medical or dental expense |
| Eligible expense, not the bill | For medical items it is the reasonable and customary amount set by each insurer; for dental, the fee in the current provincial fee guide. A provider who charges more leaves you paying the difference |
| Each plan’s own limits | Deductibles, coinsurance and maximums still apply to what each plan would pay |
| When the order can’t be set | The plans share the cost in proportion to what each would have paid as first payer |
Is a Second Plan Worth It?
If both plans are employer-paid with no cost to you, keeping both adds reimbursement at no cost. If adding a spouse or family to a second plan costs a monthly premium, the comparison is between that premium and what the second plan would have paid last year: the unpaid balances on your claims, up to the second plan’s own coverage levels and maximums. For a household with few claims, the premium can exceed the extra reimbursement; for one with regular dental, drug or paramedical claims, it often doesn’t. In a flexible benefits plan, coordinating which spouse buys which coverage can free credits for an HSA or RRSP.
Practical Tips for Dual Coverage
| Tip | Why |
|---|---|
| Keep both plans’ policy and certificate numbers on file | Faster claims, and providers need them for electronic COB |
| Tell the dentist or pharmacist about both plans | For electronic claims, identifying all your coverage to the provider is your responsibility |
| Keep copies of receipts and the first plan’s EOB | The second plan needs them for a paper claim |
| Check both plans’ maximums at the start of the year | Expenses near a maximum can be planned across the two plans |
| Get a predetermination for large dental work | Shows what each plan will pay before treatment |