The short answer
Delaying Part B without a Special Enrollment Period adds an extra 10% to your premium for each year you waited, and Medicare.gov does not say how long it lasts on its penalty page. Part D adds 1% a month — 12% a year — based on the national base beneficiary premium, and it follows you even if you change plans. Creditable drug coverage or a Special Enrollment Period prevents them.
The Part B penalty is an extra 10% for each year you delayed enrollment.
Medicare.gov gives the Part B rule (10% per year) but does not state how long it lasts on its penalty page; ask 1-800-MEDICARE how it applies to you.
The Part D penalty is 1% for each month without coverage — 12% a year.
The Part D penalty is calculated from the national base beneficiary premium, $38.99 in 2026.
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The thing that makes these penalties different
Most late fees are one-off. Medicare's are not. Both late enrollment penalties are added to your monthly premium. Medicare.gov says the Part D penalty stays for as long as you have Medicare drug coverage, even if you switch plans. Its penalty page does not say how long the Part B penalty lasts, so ask Medicare before you assume it ends.
That permanence is the reason a decision about timing, taken quickly during a difficult year, can quietly cost money for years.
These are not fines you pay once. They are added to your monthly premium.
Part B: 10% for every year
The Part B calculation is straightforward. You pay an extra 10% for each year you could have enrolled and did not, and it adds up — a two-year delay means a 20% addition to your monthly premium.
Medicare.gov works an example. Against the 2026 Part B premium of $202.90, a two-year delay produces a penalty of $40.58, taking the monthly cost to $243.50. The penalty page does not say how long this lasts, so ask Medicare.
Part D: 1% for every month
The drug coverage penalty is finer-grained and easier to accumulate without noticing. It accrues at 1% for each month you go without coverage — 12% a year — calculated against the national base beneficiary premium, which is $38.99 in 2026.
Medicare.gov's example: a 14-month gap produces a 14% penalty, adding $5.50 a month. That figure looks small next to a cancer treatment bill. But it lasts for as long as you have Medicare drug coverage, even if you switch plans.
The two ways out
Medicare.gov describes specific routes that let you delay without paying a penalty:
- For Part B: you can delay without penalty if you qualify for a Special Enrollment Period, or if you enroll in a Medicare Savings Program.
- For Part D: you escape the penalty by maintaining creditable drug coverage — coverage comparable to Part D — or by qualifying for Extra Help.
The word doing all the work in the Part D rule is creditable. Employer drug coverage is not automatically creditable simply because it exists. Ask your plan or employer whether your drug coverage is creditable, and keep the answer.
What to do if you are still working
If you have employer coverage and are approaching Medicare eligibility, three questions settle most of it:
- Is my employer's drug coverage creditable?
- Do I qualify for a Special Enrollment Period based on that employment coverage?
- When exactly does that coverage end, and what is the enrollment window that follows?
Ask your employer's benefits administrator in writing whether your coverage is creditable. Then check the timing rules with Medicare (medicare.gov) before you decide to delay anything.
Why this lands during a cancer year
A diagnosis often coincides with employment changing — reduced hours, leave, or stopping work altogether. Coverage decisions get made fast in that period, and the ones with lasting consequences are not the ones that feel urgent at the time.
If you are in treatment and near Medicare age, put this on the list of things to ask about early rather than late. Confirm your employer coverage status in writing, note the dates, and get the enrollment question answered by someone whose job it is to answer it, such as Medicare itself.
Sources
Common questions
How is the Part B penalty calculated?
You pay an extra 10% for each year you could have signed up and did not. Medicare.gov gives an example: a 2-year delay against the 2026 premium of $202.90 produces a $40.58 penalty, raising the monthly cost to $243.50.
How is the Part D penalty calculated?
It accrues at 1% for each month you went without coverage, applied to the national base beneficiary premium, which is $38.99 in 2026. Medicare.gov's example: a 14-month gap gives a 14% penalty, adding $5.50 a month.
Can I avoid the penalty if I am still working?
Medicare.gov says you can delay without penalty if you qualify for a Special Enrollment Period, or if you enroll in a Medicare Savings Program. For drug coverage, keeping creditable coverage comparable to Part D avoids the Part D penalty.
Does the penalty ever end?
Medicare.gov says the Part D penalty lasts for as long as you have Medicare drug coverage, even if you switch plans. Its penalty page does not say how long the Part B penalty lasts, so ask Medicare.
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
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