Medicare Late Enrollment Penalty Calculator
Estimate the Medicare late enrollment penalty for Part B (10% of the standard premium per full 12 months), Part D (1% of the base premium per uncovered month) and premium Part A (10% for twice the years you waited). The 2026 figures use CMS's official $202.90 Part B premium and $38.99 Part D base premium. The 2027 Part B premium is not announced, so its 2027 penalty is shown as a percent of the 2027 standard premium, plus a clearly labelled Trustees Report projection.
Maintained by Archie Chang · Figures checked against CMS and Medicare.gov October 24, 2026 · Methodology & sources
Part B late enrollment penalty
Count the months from dates
- Penalty
- 20% of the standard premium
- 2026 penalty ($202.90 standard premium)
- $40.60 a month (after rounding the total premium)
- 2026 Part B premium with penalty
- $243.50
- 2027
- 20% of the 2027 standard premium (not announced yet)
Projection, not official: at the Trustees Report estimate of $209.50, 2027 would be about $41.90 in penalty and $251.40 in total. CMS has not announced the 2027 premium.
CMS rounds the whole premium (standard plus penalty) to the nearest 10 cents, so the penalty shown is the rounded total minus the standard premium; the unrounded 2026 penalty is $40.58.
Lasts as long as you have Part B. IRMAA, if any, is added on top of this and does not enlarge the penalty.
Part D late enrollment penalty
Count the months from dates
Extra Help removes the Part D penalty and resets your uncovered months to 0. Later gaps are counted only from the day Extra Help ends.
- Penalty
- 14% of the base beneficiary premium
- 2026 monthly penalty ($38.99 base premium)
- $5.50
- 2027 monthly penalty ($41.33 base premium)
- $5.80
- 2026 total with your plan premium
- $5.50
- 2027 total if your plan premium stays the same
- $5.80
Added to your premium for as long as you have Medicare drug coverage, even if you switch plans, and recalculated each year with the base premium. A gap shorter than 63 days does not count.
Part A premium late enrollment penalty
Only for people who must buy Part A because they lack enough work credits. If you get premium-free Part A there is no Part A penalty. Months covered by an employer group health plan through current work do not count (42 CFR 406.33(a)(2)).
- Penalty
- 10% of the Part A premium
- 2026 monthly penalty
- $56.50
- 2026 Part A premium with penalty
- $621.50
- How long you pay it
- 4 years (twice the 2 full years you waited)
How each penalty works, with the official examples
| Part | Scenario | Math | Result |
|---|---|---|---|
| Part BMedicare.gov, Avoid late enrollment penalties | Waited 2 full years (24 months), no employer group-health-plan months | $202.90 + $40.58 (20%) = $243.48 | $243.50 a month in 2026 |
| Part DMedicare.gov, Avoid late enrollment penalties | Waited 14 months, no creditable coverage | 14% x $38.99 = $5.46 | $5.50 a month in 2026 |
| Part DMedicare.gov (2018 page, archived) | Mrs. Martinez: 31 uncovered months, June 2015 to December 2017 | 31% x $35.02 = $10.86 in 2018; 31% x $33.19 = $10.29 in 2019 | $10.90 in 2018, $10.30 in 2019 |
| Part AMedicare.gov, Avoid late enrollment penalties | Eligible for 2 years but did not buy Part A | $565.00 x 10% = $56.50 extra, for 4 years | $621.50 a month in 2026 if your premium is $565.00 |
Part B
The penalty is 10% of the standard premium for each full 12-month period between the end of your Initial Enrollment Period and the month you sign up (42 U.S.C. 1395r(b); 42 CFR 408.22, 408.24). Months you were covered by a group health plan through your own or your spouse's current employment are left out, even if you never used a special enrollment period (POMS HI 00805.280); months after that coverage ends count if you miss the 8-month special enrollment period (POMS HI 00805.281). For signups from 2023 on, counting runs to the end of the month you enrolled; for earlier signups it runs to the end of the enrollment period you enrolled in (the general enrollment period ends March 31). Part months do not count: 23 months is no more than 10%, 24 months is 20%. CMS rounds the whole premium to the nearest 10 cents, which is why $243.48 is billed as $243.50. The penalty is based on the standard premium, so a higher IRMAA premium does not make it bigger.
2027: a 2-year wait is 20% of the 2027 standard premium, which CMS has not announced yet. CMS usually announces it in November; See the Medicare Part B premium 2027 page. The calculator shows a labelled Trustees Report projection, never an official amount.
Part D
You owe a Part D penalty if, after your Initial Enrollment Period, there is a continuous stretch of 63 days or more with no Part D plan and no creditable drug coverage (42 CFR 423.46). The penalty is 1% of the national base beneficiary premium for each uncovered month (42 CFR 423.286(d)(3)), rounded to the nearest $0.10. It is recalculated every year using that year's base premium: $38.99 for 2026 and $41.33 for 2027 (CMS, July 28, 2026). The same 14 months costs $5.50 in 2026 and $5.80 in 2027. Part D IRMAA is separate and also added to your premium; see the IRMAA brackets for 2027 and the IRMAA calculator.
Part A (only if you buy it)
Most people get Part A free and never face a Part A penalty. If you must buy it ($565.00 a month in 2026, or $311.00 with 30 to 39 work credits) and wait, the premium rises 10%, no matter how long you waited, for twice the number of full years you could have signed up (42 U.S.C. 1395i-2(a)(6); 42 CFR 406.32(d)). Months covered by an employer group health plan through current work do not count (42 CFR 406.33(a)(2)).
Creditable coverage, the 8-month special enrollment period and Extra Help
Creditable drug coverage is coverage expected to pay at least as much as Medicare's standard Part D. Your employer, union, VA or TRICARE plan sends a yearly notice saying whether it is creditable. Keep those notices: they are your proof if the plan or CMS questions the penalty. A month in which you had creditable coverage for any part of it is not an uncovered month.
Part B and employer coverage. If you were covered by a group health plan through your own or your spouse's current employment, you can sign up for Part B without a penalty during a special enrollment period that runs through the eighth full month after that coverage or the employment ends (42 U.S.C. 1395p(i)(3); 42 CFR 407.20). Months covered by that plan are not counted; months after it ends are counted if you miss the window, so enter only the countable months. The clock starts when the work or the job-based coverage ends, whichever is first, even if you keep COBRA; retiree coverage and individual marketplace plans do not qualify you for it.
Extra Help. People who qualify for the Part D Low-Income Subsidy are not charged a Part D late enrollment penalty (42 CFR 423.780(e)). Extra Help removes the Part D penalty and resets your uncovered months to 0. Later gaps are counted only from the day Extra Help ends. (CMS Prescription Drug Benefit Manual Chapter 4, sections 30.1.4 and 50.4.) Tick the box in the calculator to see the penalty at zero.
Reconsideration. If you disagree with a Part D penalty, ask for a reconsideration within 60 days of the notice, with proof of creditable coverage (Medicare.gov, "Avoid late enrollment penalties"; CMS Chapter 4 guidance). You pay the penalty while it is pending.
What this calculator does not model
- Whether your months are countable. Months covered by a group health plan through your or your spouse's current employment are not counted, and months after that coverage ends count if you miss the 8-month special enrollment period; this tool does not check eligibility, so enter only the countable months.
- Equitable relief or reconsideration decisions by CMS, SSA or the Part D reconsideration contractor.
- Medicare Advantage and Medicare Advantage drug plan specifics, including Part B premium reductions some plans offer.
- The Part B and Part D penalty clock for people who got Medicare under 65 because of disability and reach age 65 (they get a new initial enrollment period).
- State buy-in, Medicare Savings Programs and other Medicaid help that pay the Part B premium or change the months counted.
- Income-related monthly adjustment amounts (IRMAA): the penalty is computed on the standard premium and IRMAA is added on top.
- The hold harmless rule, which limits a Part B premium increase for some people whose premium comes out of Social Security.
Rounding: Part B premiums are rounded to the nearest 10 cents by statute (42 U.S.C. 1395r(c)). The Part D penalty is rounded to the nearest 10 cents per CMS Prescription Drug Benefit Manual Chapter 4, section 20.4; statute and regulation do not say so. Neither source says how an exact half-dime rounds; this calculator rounds it up (an assumption). The Part A premium is a whole dollar amount, so 10% of it is always a multiple of 10 cents.
Frequently asked questions
How is the Part D late enrollment penalty calculated?
Medicare multiplies 1% by the national base beneficiary premium by the number of full months you could have had Part D but did not, and had no creditable drug coverage. The result is rounded to the nearest $0.10 and added to your plan premium. With the $38.99 base premium for 2026, 14 uncovered months is 14% x $38.99 = $5.46, rounded to $5.50 a month (Medicare.gov's own example). The base premium changes each year, so the penalty does too; for 2027 CMS set it at $41.33.
How much is the Part B late enrollment penalty?
10% of the standard Part B premium for each full 12-month period you could have had Part B but did not, not counting months you were covered by an employer group health plan through current work. The standard premium is $202.90 in 2026, so a 2-year wait is 20%: $40.58 on top of $202.90, or $243.48, rounded to $243.50 (Medicare.gov's own example). For 2027 a 2-year wait is 20% of the 2027 standard premium, which CMS has not announced yet.
Does the Medicare penalty last forever?
The Part B and Part D penalties last as long as you have that coverage, which for most people is for life. They are not one-time fees. The Part A premium penalty is different: it is 10% and you pay it for twice the number of years you could have signed up but did not, so 2 years of delay means 4 years of the higher premium. Extra Help removes the Part D penalty and resets your uncovered months to 0. Later gaps are counted only from the day Extra Help ends.
How do I avoid the late enrollment penalty?
Sign up for Part B and Part D during your Initial Enrollment Period, or keep creditable coverage. If you or your spouse are still working and covered by an employer plan, you can delay Part B without a penalty and sign up during the 8-month special enrollment period that starts when the employment or the coverage ends, whichever comes first. For Part D, join a plan within 63 days of losing creditable drug coverage. The clock starts even if you keep COBRA, and COBRA or retiree coverage does not make you eligible for the special enrollment period on its own.
Can I appeal a Part D late enrollment penalty?
Yes, you can ask for a reconsideration. A Medicare contractor that is not connected to your drug plan reviews it. You generally must ask within 60 days of the date on the letter telling you about the penalty, and include proof of creditable coverage such as a notice from an employer or union plan. You still have to pay the penalty with your premium while the request is pending. The decision is not subject to further appeal, though CMS can revise it.
Related Medicare and Social Security tools
Sources: Medicare.gov: Avoid late enrollment penalties · Medicare.gov: Part D costs · 42 U.S.C. 1395r (Part B) · 42 U.S.C. 1395w-113 (Part D) · 42 U.S.C. 1395i-2 (Part A) · 42 CFR 408.22 · 42 CFR 408.24 · 42 CFR 423.46 · 42 CFR 423.286 · 42 CFR 406.32 · 42 CFR 406.33 · CMS Part D manual, Chapter 4 · SSA POMS HI 00805.280 · SSA POMS HI 00805.281 · CMS 2026 Part B premium fact sheet · CMS 2027 Part D base premium
Medicare Late Enrollment Penalty Calculator: Part B and D. Estimate only; Medicare and Social Security notices are authoritative.