Creditable coverage part d is the plain reason so many people who work past 65 never pay a drug penalty. It comes down to one letter. Each year your employer or plan sponsor must tell you whether the drug coverage in your group plan is at least as good as standard Medicare Part D. That letter is called a Creditable Coverage Disclosure Notice. CMS requires plan sponsors to send it to Part D–eligible members at least once a year, before October 15.
If the letter says your drug coverage is creditable, you can keep working, keep your plan, and delay Part D without a penalty. If it says non-creditable, the clock starts. The creditable coverage part d rules are described by CMS on Creditable Coverage and Late Enrollment Penalty.
The Rule Behind Creditable Coverage Part D
Two separate rules run at the same time. One decides who pays your medical bills first. The other decides whether you owe a Part D penalty later.
The payer rule turns on employer size. If the employer has 20 or more employees, the group health plan generally pays first and Medicare pays second. If the employer has fewer than 20 employees, Medicare generally pays first. That second case matters. If Medicare is primary and you have not enrolled, the group plan may pay almost nothing.
The creditable coverage part d rule is different. It does not care about employer size at all. It only asks whether your drug coverage is expected to pay, on average, as much as standard Part D coverage. A small employer can offer creditable drug coverage. A large employer can offer non-creditable drug coverage.
So a creditable coverage part d letter protects you from the drug penalty. It does not tell you who pays first. Confirm the size rule with your benefits administrator in writing.
Your Choices at 65
Part A is premium-free for most people with 40 quarters of work. Part B costs $202.90 a month at the standard 2026 rate. Part D is a separate plan you buy. Your job is to decide which of the three to take now.
| Your situation | Who generally pays first | What to do |
|---|---|---|
| Employer with 20+ employees, coverage through current work | Group health plan first, Medicare second | You may delay Part B and Part D. Keep the creditable coverage letter. |
| Employer with fewer than 20 employees | Medicare first, group plan second | Ask the plan in writing. Most people in this group enroll in Part A and Part B at 65. |
| Under 65 and Medicare-eligible by disability, employer with 100+ employees | Group health plan first | You may delay Part B. Confirm with the plan. |
| Under 65 by disability, employer with fewer than 100 employees | Medicare first | Enrolling in Part B at eligibility is usually the safer path. |
| COBRA, retiree plan, or Marketplace coverage | Medicare first | This is not current employment. The Part B special enrollment period does not apply. |
| Contributing to an HSA | Depends on employer size | Any Medicare enrollment ends HSA eligibility. Read Publication 969 first. |
Keep every annual notice. A creditable coverage part d letter from six years ago is the evidence that closes a penalty dispute six years from now.
The Penalty If You Get It Wrong
The Part D penalty has a simple formula. Medicare takes 1% of the national base beneficiary premium, which is $38.99 for 2026. It multiplies that by the number of full months you went without Part D or creditable drug coverage. The result is rounded to the nearest ten cents.
Say you go 30 full months uncovered. That is 30% of $38.99, or about $11.70 a month, added to your plan premium. The base premium changes each year, so the penalty amount moves with it. See Medicare drug coverage costs.
The trigger is a gap of 63 days or more in a row after your Initial Enrollment Period ends. Sixty-two days is not a penalty. Sixty-three is.
The Part B penalty works differently. It is 10% of the standard premium for each full 12-month period you could have had Part B and did not. Two full years late means roughly 20% more, every month.
Both penalties last as long as you keep the coverage. For most people that means the rest of their life. Medicare explains this at Avoid late enrollment penalties.
Creditable Coverage Part D: the Paperwork
When you finally leave the employer plan, two forms do the work. Form CMS-40B, Application for Enrollment in Medicare Part B, is signed by you. Form CMS-L564, Request for Employment Information, has two sections. You complete Section A. Your employer or plan administrator completes and signs Section B.
Send both forms together to Social Security. You can mail, fax, or upload them. Instructions are on Sign up for Part B only and the blank forms are at Medicare enrollment forms.
The Part B Special Enrollment Period runs 8 months from the month employment or the group coverage ends, whichever comes first. The Part D window is much shorter. It is 2 full months after the month your creditable coverage ends, or 2 months after you are notified, whichever is later.
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If the employer will not sign Section B, ask Social Security what secondary proof it accepts. Pay stubs, W-2s, and the plan’s own creditable coverage part d notices are often used. Get the current form here: CMS-L564 and CMS-40B.
The Traps People Fall Into
COBRA is the first trap. COBRA is not coverage based on current employment. Taking COBRA at 65 does not extend your Part B special enrollment period. Its drug benefit may still be creditable for Part D purposes, which is why the letter matters separately.
Retiree coverage is the second. Retiree plans usually pay second to Medicare. Many require you to enroll in Part A and Part B. Some retiree plans are creditable for drugs and some are not. Read the notice, not the summary.
HSA contributions are the third. You cannot contribute to an HSA for any month you are enrolled in any part of Medicare. Part A can be granted retroactively, up to six months back, when you enroll after 65. Many advisers stop contributions six months ahead for that reason.
The 2026 HSA limits are $4,400 self-only and $8,750 family, with a $1,000 catch-up at 55 or older, under Rev. Proc. 2025-19. Excess contributions can trigger tax. Review IRS Publication 969 with your tax preparer.
Small employers are the fourth. Under 20 employees usually means Medicare pays first. Skipping Part B there can leave large bills unpaid, even with creditable coverage part d protection on the drug side.
Frequently Asked Questions
What if I never received the letter?
Ask your benefits administrator for a written statement of whether the plan’s drug coverage is creditable. Plan sponsors must issue the notice annually before October 15. Request copies for every year you were covered. There is no substitute for that written record.
Does creditable coverage part d protect me from the Part B penalty too?
No. They are separate rules. Creditable coverage part d addresses drug coverage only. Part B protection comes from coverage based on current employment and is documented with Form CMS-L564.
Can I dispute a penalty Medicare already assessed?
Yes, there is a reconsideration process. Your plan sends a notice with a form and a deadline stated on it. CMS describes it under Late Enrollment Penalty Appeals. Submit the creditable coverage part d letters covering the disputed months.
My spouse is 65 and I am still working. Which rules apply?
Coverage through a spouse’s current employment can count for both the Part B special enrollment period and creditable coverage part d. Employer size still controls who pays first. Confirm the details with the plan and with Social Security at 1-800-772-1213 before you decide.
Compare Your Options
Once you know what creditable coverage part d 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.