Delaying Medicare Part B is a normal, permitted choice for people who are still working at or past 65. It is not a loophole. Federal rules let you postpone Part B if you have group health coverage based on current employment. But the protection is not automatic. It depends on how many employees your employer has, whether the job is still active, and whether you file the correct forms when you do enroll. Get it wrong and you can carry a premium surcharge for life.
This guide walks through the rule, the forms, the deadlines, and the traps. Confirm your own dates with the Social Security Administration before you act on any of it.
The Rule Behind Delaying Medicare Part B
The rule turns on employer size. Medicare’s coordination of benefits rules ask one question first: who pays first, the group plan or Medicare? If the employer has 20 or more employees, the group health plan is primary and Medicare is secondary. That is the situation in which delaying medicare part b is generally safe.
If the employer has fewer than 20 employees, the arrangement usually flips. Medicare becomes the primary payer and the group plan pays second. In that case, delaying medicare part b can leave most of your bills unpaid, because the small group plan may only cover what Medicare would have covered second. Ask your benefits administrator, in writing, which payer is primary.
The coverage must also be based on current employment — yours or your spouse’s. Retiree coverage and COBRA are not current employment coverage. Medicare explains how enrollment timing works on when Medicare coverage starts.
Your Choices at 65
You have three realistic paths. Take Part A only and keep the employer plan. Take Part A and Part B together. Or delay both. Most people with large-employer coverage take premium-free Part A and postpone Part B. That choice has an HSA consequence, covered below.
| Employer size | Who pays first | What to consider doing |
|---|---|---|
| 20 or more employees (active work) | Group health plan pays first; Medicare pays second | Part B may be delayed. Keep proof of continuous coverage. Use the Special Enrollment Period later. |
| Fewer than 20 employees (active work) | Medicare pays first; group plan pays second | Enrolling in Part B at 65 is usually expected. Confirm with the plan administrator before delaying. |
| COBRA after employment ends | Medicare pays first | COBRA is not current employment coverage. Delay is generally not protected. |
| Retiree group coverage | Medicare pays first | Not current employment coverage. Delay is generally not protected. |
| Spouse still working, 20+ employees | Spouse’s group plan pays first | Delay may be available through the spouse’s active coverage. |
| TRICARE, VA, or Marketplace plan | Varies by program | These are not employer group coverage. Confirm rules with that program directly. |
Notice the pattern. Delaying medicare part b is tied to active employment, not to simply having insurance. Any coverage that continues after the job ends changes the answer.
The Penalty If You Get It Wrong
The Part B late enrollment penalty is 10% of the standard premium for each full 12-month period you could have had Part B but did not. It is added to your monthly premium. In most cases you pay it for as long as you have Part B. Medicare describes this on its page about avoiding late enrollment penalties.
The arithmetic is simple. The standard Part B premium for 2026 is $202.90 per month, per the CMS premium announcement. Two full uncovered years would mean a 20% surcharge. That is about $40.58 added each month, and the percentage is applied to the premium as it rises each year.
Part D has its own penalty. It equals 1% of the national base beneficiary premium — $38.99 for 2026 — multiplied by the number of full uncovered months without creditable drug coverage. It is rounded to the nearest 10 cents and added for as long as you have Part D coverage. Creditable coverage through an employer plan prevents it.
Both penalties are lifetime charges in the ordinary case. There is no routine appeal simply because delaying medicare part b felt reasonable at the time. Social Security decides whether an exception applies.
Delaying Medicare Part B: the Paperwork
Two forms do the work. CMS-40B, Application for Enrollment in Medicare Part B (Medical Insurance), is signed by you. You can download it from CMS Form 40B or the CMS-40B form page.
CMS-L564, Request for Employment Information, is the proof form. You complete Section A with your name and employer. Your employer’s human resources or benefits officer completes and signs Section B, listing the dates the group health plan covered you based on current employment. An employer signature is what makes delaying medicare part b defensible on the record.
Both forms are listed on Medicare’s enrollment forms page. Submit them to Social Security. Filing methods and current mailing or upload instructions are on the SSA page for signing up for Part B only. Check that page for the accepted method before you send anything.
Timing matters most. The Special Enrollment Period generally runs for 8 months after employment or the group health coverage ends, whichever happens first. Many people also use the 8-month window that starts the month after employment ends. Confirm the exact start date of your window with SSA, in writing.
If your employer will not sign CMS-L564, do not stop. Social Security may accept other evidence of coverage, such as pay stubs, W-2 forms showing pre-tax premium deductions, or health insurance cards with dates. Ask an SSA representative what secondary proof they will accept in your case, and keep a record of who told you.
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The Traps People Fall Into
COBRA is the most common trap. COBRA is not coverage based on current employment. Continuing COBRA after 65 while delaying medicare part b does not protect you from the penalty, and COBRA usually pays second once you are Medicare-eligible. Retiree coverage carries the same problem.
HSAs are the second trap. Under IRS rules described in Publication 969, Health Savings Accounts and Other Tax-Favored Plans, your HSA contribution limit becomes zero starting the first month you are enrolled in Medicare.
Premium-free Part A can be backdated up to 6 months when you enroll after 65, though never earlier than the month you turned 65. Contributions made during that retroactive window become excess contributions. Many advisers suggest stopping HSA contributions 6 months before applying. Confirm your own dates with a tax professional.
Small employers are the third trap. A 15-person company plan may quietly pay second. The gap does not appear until a large claim arrives. Ask for the answer in writing.
Frequently Asked Questions
Does delaying medicare part b require me to notify Social Security at 65?
If you are not receiving Social Security benefits, you generally take no action. If you are already receiving benefits, you are enrolled automatically and must follow the refusal instructions that come with your Medicare card. Contact SSA to confirm what applies to you.
Can I take Part A and delay Part B?
Yes, that combination is common for people with large-employer coverage. Remember the HSA consequence. Once Part A begins, including retroactively, HSA contributions must stop.
When does Part B start after I file CMS-40B?
For enrollments during the Special Enrollment Period tied to employment, coverage generally begins the month after Social Security receives your completed application, or on a later date you request. Ask SSA to confirm your effective date in writing before you drop employer coverage.
What happens if I miss the 8-month window?
You may have to wait for the General Enrollment Period, which runs January 1 through March 31, and the late enrollment penalty may apply. Some people qualify for an exceptional-conditions Special Enrollment Period. Ask SSA whether one covers your situation.
Key Takeaways: Delaying Medicare Part B
- Employer size decides everything. Whether delaying medicare part b is a choice or a requirement turns on the 20-employee rule.
- Part A is usually free. Most people take it at 65 even when delaying medicare part b lets them delay Part B.
- Except with an HSA. Part A ends HSA contributions, the one case where delaying medicare part b means delaying Part A too.
Compare Your Options
Once you know what delaying medicare part b means for you, the official Plan Finder shows what is actually sold in your ZIP code, and a SHIP counselor will walk it with you for free — no commission, no sales call.
Official Sources & Resources
- Social Security — Medicare enrollment: https://www.ssa.gov/medicare
- IRS Publication 969 (HSAs): https://www.irs.gov/publications/p969
- Medicare.gov: https://www.medicare.gov
- CMS.gov: https://www.cms.gov
- Find your SHIP counselor: https://www.medicare.gov/talk-to-someone
Checked against the official sources above in September 2026. Rules and dollar figures change; if a notice you received disagrees with this page, the notice wins — and please tell us. General information, not legal, financial or medical advice.