When Medicare Becomes Your Primary Insurance

Medicare is primary when it is the first payer for your medical bills

Primary insurance means Medicare pays its share of your covered costs before any other insurance you have. Secondary insurance pays what Medicare does not cover, up to its own limits. Whether Medicare is primary or secondary depends on your age, your employment status, and what other coverage you carry.

Most people over 65 have Medicare as primary. But if you are still working and your employer offers health insurance, or if you have coverage through a spouse's job, that employer plan may be primary instead. The rules are specific, and getting them wrong can mean unexpected bills or delayed claims.

Key Takeaways

Medicare is usually primary for people 65 and older who are not actively working, or who work for an employer with fewer than 20 employees.
If you work for an employer with 20 or more employees and have health insurance through that job, the employer plan is primary and Medicare is secondary.
If you are under 65 and have Medicare due to disability or end-stage renal disease, an employer plan is primary if you are still working.
You must tell both Medicare and your other insurance which is primary, or claims may be delayed or denied.
When Medicare is secondary, you pay your employer plan's deductible and copays first, then Medicare covers its portion of what remains.

Medicare is primary if you are 65 or older and not working

If you are 65 or older and have no health insurance through an employer, Medicare is your primary insurance. This covers most retirees. Your Medicare Part A (hospital) and Part B (doctor visits) are the first payers, and any supplemental or secondary coverage you buy picks up what Medicare leaves behind.

This is the most straightforward situation. When you turn 65 and sign up for Medicare, you do not need to coordinate with another plan unless you choose to buy a Medigap policy or a Medicare Advantage plan that includes supplemental coverage.

Employer coverage is primary if you work and your employer has 20 or more employees

If you are 65 or older, still working, and your employer has 20 or more employees, your employer health plan is primary. Medicare becomes secondary. This rule applies whether you work full-time or part-time, and it applies to spouses' employer plans as well.

The 20-employee threshold is the key number. An employer with 19 employees does not trigger this rule. If you are unsure of your employer's size, ask your human resources or benefits department.

When your employer plan is primary, you use that insurance first for all claims. Medicare only pays after your employer plan has paid its share. You will still pay your employer plan's deductible, copays, and coinsurance before either plan pays anything.

Medicare is primary if your employer has fewer than 20 employees

If you are 65 or older, working, and your employer has fewer than 20 employees, Medicare is primary even though you have employer coverage. Your employer plan becomes secondary and covers costs Medicare does not pay.

This rule protects people who work for small businesses. It means you can rely on Medicare as your main coverage without waiting for a small employer plan to process claims first.

Rules change if you are under 65 with Medicare

If you are under 65 and have Medicare because of disability or end-stage renal disease, the rules are different. If you are working and have health insurance through your job, your employer plan is primary and Medicare is secondary, regardless of your employer's size.

This applies for the first 30 months after you become may be able to access for Medicare due to disability. After 30 months, Medicare becomes primary. If you have end-stage renal disease, your employer plan is primary for the first 12 months after your Medicare may be able to access begins, then Medicare takes over.

Keep track of these dates. When the switchover happens, you need to notify both your employer plan and Medicare so claims process correctly.

How to tell Medicare and your other insurance which is primary

You must report your employment and other coverage to Medicare. When you first sign up for Medicare, you will be asked whether you have other health insurance. If your situation changes — you start working, you retire, or your employer coverage ends — you need to update Medicare within 30 days.

Contact Medicare at 1-800-MEDICARE or log into your Medicare account at Medicare.gov. You will need your employer's name and the date your coverage began or ended.

Also tell your employer plan that Medicare exists. Give your employer's benefits department your Medicare card and the date you became may be able to access. They need this information to coordinate benefits correctly and to know whether to process claims first or second.

If you do not report correctly, claims may be denied or delayed while the two insurers figure out who should pay. This can take weeks and may result in bills sent to you.

What happens when claims are processed with the wrong primary insurance

If your employer plan thinks it is secondary but Medicare thinks it is primary, the claim may be rejected by one or both insurers. You may receive a bill, or the claim may sit in limbo while the insurers contact each other.

If you receive a bill you believe is wrong, ask the provider's billing department which insurance they billed first. Then contact that insurance and ask them to correct the claim with the right primary and secondary designation. Keep copies of all correspondence.

If the problem is not resolved within 30 days, contact your state's insurance commissioner's office. They can investigate coordination-of-benefits disputes.

Frequently Asked Questions

If I go back to work after retiring, does my employer plan become primary?

Only if your employer has 20 or more employees. If it does, your employer plan becomes primary when ready when you are hired. Notify Medicare within 30 days so they know to process claims as secondary. If your employer has fewer than 20 employees, Medicare stays primary.

What if I have Medicare and COBRA coverage from a previous job?

COBRA is employer coverage, so the 20-employee rule applies. If the employer had 20 or more employees, COBRA is primary and Medicare is secondary. If the employer had fewer than 20, Medicare is primary. You pay COBRA premiums either way, but the order of payment changes.

Do I need to keep my employer plan if Medicare is primary?

No, but it may be worth keeping if it covers services Medicare does not, such as dental or vision. If you drop employer coverage while still working, make sure you have other coverage for what Medicare does not pay, or you will face large out-of-pocket costs.

What if my spouse is still working and I am retired?

If you are 65 or older and retired, Medicare is your primary insurance. Your spouse's employer plan does not affect your coverage. Your spouse's plan is primary for your spouse only if your spouse is 65 or older and working for an employer with 20 or more employees.

When should I contact Medicare about a change in my work status?

Contact Medicare within 30 days of any change: when you start working, when you retire, when your employer coverage begins or ends, or when your employer's size changes in a way that affects the 20-employee rule. Waiting longer can result in claims being processed with the wrong primary insurance.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.