Part B 10% per Year · Part D 1% per Month · 2027 Base Premium $41.33 · Lifetime Cost
Medicare Late Enrollment Penalty Calculator
Missed your Medicare sign-up window? Enter how long you went without Part B or drug coverage to see the monthly penalty Medicare adds to your premium, the way SSA and CMS compute it: full 12-month periods for Part B, uncovered months for Part D, rounded to the dime, plus what it costs over the years you expect to pay it.
Penalty Inputs
Sets the Part D base beneficiary premium: $38.99 for 2026, $41.33 for 2027 (CMS).
Months after your Initial Enrollment Period ended until you signed up. Leave out months you had job-based group coverage from your or your spouse's current work. Enter 0 if you enrolled on time.
$202.90 is the 2026 standard premium. CMS had not published the 2027 premium as of October 25, 2026; replace this when it does. Do not add IRMAA: the penalty is figured on the standard premium.
Full months after your Initial Enrollment Period with no Part D plan and no creditable drug coverage.
Medicare charges no Part D penalty unless a single break lasted 63 days or longer.
People who qualify for Extra Help pay no Part D late enrollment penalty while they have it.
2026 amounts. Only people who must buy Part A can owe a Part A penalty.
The Part A penalty is a flat 10% and lasts twice this many years.
For the cost projection only. It holds this year's amounts flat; real penalties rise when premiums rise.
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Enter how long you went without coverage to see your monthly Medicare penalty
Late Enrollment Penalty
Part B: the standard premium you enter, increased 10% for each full 12 months late, rounded to the nearest 10 cents (Social Security Act §1839(b)-(c); POMS HI 01001.010). Part D: 1% of the national base beneficiary premium for each uncovered month, rounded to the nearest $0.10 (42 CFR 423.286(d)(3)). Part A: 10% of the premium for twice the years late (Medicare.gov). The projection holds this year's amounts flat. Your penalty notice from SSA or your drug plan controls. Educational estimate only.
Want the full rules - which months count, how the employer-coverage Special Enrollment Period works, what counts as creditable drug coverage, and how to ask Medicare to reconsider a penalty? Read the companion guide.
The Part B penalty is 10% of the standard premium for each full 12 months you could have had Part B but did not; 26 months late is a 20% penalty, or $40.60 a month on the 2026 premium of $202.90. The Part D penalty is 1% of the national base beneficiary premium for each full month without creditable drug coverage, rounded to the nearest dime; 17 months is $6.60 a month in 2026 (base $38.99) and $7.00 in 2027 (base $41.33). Both are added to your premium for as long as you have that coverage, and both are recalculated every year from the new premium.
Key Takeaways
Part B: 10% per full 12-month period late, applied to the standard premium ($202.90 in 2026), for as long as you have Part B.
Part D: 1% per uncovered month of the base beneficiary premium ($38.99 for 2026, $41.33 for 2027), rounded to the nearest $0.10.
The 63-day rule: no Part D penalty unless a single break in creditable drug coverage lasted 63 days or more.
Part A: only if you must buy it; a flat 10% for twice the number of years you were late.
Employer coverage protects you: months with group coverage from current employment do not count, and you get an 8-month window after it ends.
Extra Help and Medicare Savings Programs: Extra Help removes the Part D penalty; enrolling in a Medicare Savings Program generally removes the Part B penalty.
Tax angle: the penalty is part of the premium, and Medicare premiums are medical expenses under IRS Publication 502.
Medicare has three late enrollment penalties, and each uses a different clock, a different base and a different rounding rule. The tool runs them separately and adds them up. For the enrollment rules behind the months you enter, see the Medicare Late Enrollment Penalty Guide.
Part B: 10% for Each Full 12 Months Statute
Section 1839(b) of the Social Security Act increases the standard monthly premium "by 10 percent of the monthly premium so determined for each full 12 months" in which you could have been, but were not, enrolled. The tool divides your months late by 12 and drops the remainder, so 11 months is 0% and 35 months is 20%. It then increases the standard premium you enter by that percentage and rounds the result to the nearest 10 cents, as section 1839(c) and SSA's POMS HI 01001.010 require (5 to 9 cents rounds up). The penalty shown is the rounded premium minus the standard premium.
The base is the standard premium only. Section 1839(b) applies the increase "without regard to" the income-related adjustment, so IRMAA is charged separately and is not multiplied by the penalty.
Part D: 1% for Each Uncovered Month CMS
Under 42 CFR 423.286(d)(3), the penalty is 1% of the national base beneficiary premium for each uncovered month. Medicare's fact sheet gives the formula as 1% x national base beneficiary premium x number of full months without Part D or creditable coverage, rounded to the nearest $0.10. The base is $38.99 for 2026 and $41.33 for 2027. The penalty applies only if you had a continuous break of 63 days or more after your Initial Enrollment Period (42 CFR 423.46), and not while you get Extra Help.
Part A: 10% for Twice the Years Late Medicare.gov
Most people get Part A free. If you have to buy it and did not sign up when first eligible, Medicare.gov says your premium "may go up 10%" and you pay the higher premium "for twice the number of years you didn't sign up." The tool applies 10% to the 2026 premium you pick ($311 or $565) and limits the projection to twice the years you enter.
The Projection Assumption
The cost projection multiplies this year's monthly penalties by 12 and by the years you enter. It does not guess future premiums. Because both penalties are percentages of a premium that is reset each year, the real dollar cost has usually been higher than a flat projection.
Medicare Penalty Figures for 2026 and 2027
Penalty bases (CMS and Medicare.gov)
Item
2026
2027
Part D national base beneficiary premium
$38.99
$41.33
Part D penalty per uncovered month (1%, before rounding)
$0.3899
$0.4133
Part B standard monthly premium
$202.90
Not yet published by CMS
Part B penalty per full 12 months late (10%)
$20.29
10% of the 2027 premium
Part A premium if bought (under 30 / 30-39 quarters)
$565 / $311
Not yet published by CMS
Part A penalty (10%), paid for twice the years late
$56.50 / $31.10
10% of the 2027 premium
CMS announced the 2027 base beneficiary premium on July 28, 2026. The Inflation Reduction Act limits its annual increase to 6% from 2024 through 2029. The 2027 Part A and Part B premiums are normally announced in the fall; until CMS publishes them, enter the new Part B figure yourself when it is out.
Worked Examples
Example 1 - Part D, Medicare's own example: 17 uncovered months in 2026
17% x $38.99 base premium$6.6283
Rounded to the nearest $0.10$6.60 per month
Same 17 months in 2027: 17% x $41.33 = $7.0261$7.00 per month
Example 2 - Part D, Medicare's Extra Help example: 12 counted months
12% x $38.99$4.6788
Rounded to the nearest $0.10$4.70 per month
Months while she had Extra HelpNot counted
Example 3 - Part B, 26 months late in 2026
26 months = 2 full 12-month periods20%
$202.90 x 1.20 = $243.48, to the nearest dime$243.50
Monthly penalty ($243.50 - $202.90)$40.60 per month
Example 4 - Part B, 11 months late versus 12 months late
11 months: no full 12-month period$0.00
12 months: $202.90 x 1.10 = $223.19, to $223.20$20.30 per month
Example 5 - Part A bought at $565, 3 years late, 20-year projection
10% x $565$56.50 per month
Paid for twice the 3 years late6 years
$56.50 x 12 x 6$4,068.00 total
Practitioner Insight (LMN Tax Inc.)
LMN Tax Inc. - Planning Notes
The penalty calls we get are rarely about people who forgot Medicare. They are about people who thought they had other coverage that counted. The most common: a client retired at 66, took COBRA, and assumed COBRA protected Part B. It does not. The 8-month Special Enrollment Period starts when the job ends, not when COBRA ends, so a client who rides 18 months of COBRA can walk straight into a General Enrollment Period, a gap and a lifetime 10% surcharge.
The second pattern is drug coverage. Retiree and marketplace plans are not automatically creditable for Part D. The plan must tell you in writing each year whether its drug coverage is creditable; we ask clients for that notice and keep it, because it is the evidence Medicare's contractor wants if a plan later flags a gap.
The third is the client who was penalised and has stopped noticing. A Part D penalty on a $0-premium plan still shows up on the bill. When a client qualifies for Extra Help, the Part D penalty stops while they have it, so we check eligibility before the next plan year rather than letting it run.
On the tax side, a late enrollment penalty is part of the Medicare premium, so it goes into the same medical-expense total as the premium itself. For our self-employed clients it is worth checking whether the premiums belong on Form 7206 instead of Schedule A.
When This Calculator Does Not Cover Your Situation
Counting the months. The tool takes the months you enter. SSA counts Part B months from the end of your Initial Enrollment Period to the end of the month you enroll (for enrollments from 2023), excludes months with employer group coverage from current work, and has older rules for enrollments before 2023. Your SSA notice is the authority.
Disability before 65. A Part B penalty charged while you were under 65 on disability ends the month you turn 65, and months before 65 never count toward a later penalty. The tool does not apply that rollback.
Re-enrollment. If you dropped Part B and re-enrolled, SSA adds the earlier surcharge months to the new gap. Enter the combined countable months.
Exceptional circumstances. Using an Exceptional Conditions Special Enrollment Period, such as one for a disaster or for incorrect information from an employer, removes the Part B penalty for the months it covers. Enter only the months that still count.
Medicare Savings Programs and state buy-in. If your state pays your Part B premium, you generally owe no Part B penalty. The tool does not check eligibility.
Part D reconsideration. If you had creditable coverage your plan did not know about, a successful reconsideration can reduce or remove the penalty. The tool assumes the months you enter stand.
Future years. The projection holds this year's premiums flat. Each year the penalty is recalculated from the new standard or base premium.
Frequently Asked Questions
How is the Medicare Part B late enrollment penalty calculated?
Your Part B premium goes up 10 percent of the standard premium for each full 12-month period you could have had Part B but did not sign up, counted from the end of your Initial Enrollment Period to the month you enroll. Partial years do not count: 26 months late is two full periods, a 20 percent penalty. With the 2026 standard premium of $202.90, that is $202.90 x 1.20 = $243.48, rounded to the nearest dime as $243.50, so the penalty is $40.60 a month. Months covered by an employer group health plan based on your or your spouse's current employment are not counted.
How is the Part D late enrollment penalty calculated?
Medicare multiplies 1 percent of the national base beneficiary premium by the number of full months you went without Part D or other creditable prescription drug coverage, and rounds the result to the nearest $0.10. It applies only if you had a break of 63 days or more in a row after your Initial Enrollment Period. Medicare's own example: 17 uncovered months x 1% x $38.99 (the 2026 base premium) = $6.63, rounded to $6.60 a month. For 2027 the base beneficiary premium is $41.33, so the same 17 months cost $7.00 a month.
Is the Medicare late enrollment penalty permanent?
For most people, yes. The Part B penalty is charged for as long as you have Part B, and the Part D penalty for as long as you have Medicare drug coverage, even if you switch plans or join a $0-premium plan. The penalty is recalculated each year from that year's premium, so the dollar amount usually rises. Two exceptions: the Part A penalty lasts twice the number of years you were late, and a Part B penalty charged while you were under 65 on disability ends when you turn 65.
How do I avoid the Medicare Part B penalty if I am still working?
If you or your spouse have group health coverage based on current employment, you can delay Part B without a penalty and use a Special Enrollment Period later. It lasts 8 months after the employment or the group coverage ends, whichever happens first. COBRA and retiree coverage do not count as current employment, and the 8 months start when the job ends even if you choose COBRA. Sign up within that window, with the employer-completed form showing your coverage, and no penalty applies.
What is the 2027 Part D base beneficiary premium?
CMS set the 2027 national base beneficiary premium at $41.33 a month on July 28, 2026, up from $38.99 for 2026. The Inflation Reduction Act caps annual growth in the base premium at 6 percent from 2024 through 2029. Medicare uses this figure only as the starting point for the penalty formula and the plan premium calculation; your own plan's premium can be higher or lower.
Can I deduct Medicare premiums and late enrollment penalties on my taxes?
The penalty is part of your Medicare premium, and IRS Publication 502 lists Part B premiums, Part D premiums and voluntarily purchased Part A premiums as medical expenses. They count toward the itemized medical expense deduction on Schedule A, which is limited to the amount above 7.5 percent of your adjusted gross income. Self-employed people can count Medicare premiums toward the self-employed health insurance deduction figured on Form 7206, and people 65 or older can pay Medicare premiums (but not Medigap) with tax-free HSA distributions.
What to Do Next
If You Have Not Signed Up Yet
Every month you wait can add to the penalty. Check whether your current coverage counts with the Medicare Late Enrollment Penalty Guide, and sign up in your Special Enrollment Period or the next General Enrollment Period (January 1 to March 31).
If You Received a Part D Penalty Notice
If you had creditable drug coverage the plan did not know about, return the reconsideration form within 60 days of the notice, with the creditable coverage letter from your employer or union plan.
If Your Income Is Also High
The penalty is separate from the income-related surcharge. Estimate both with the IRMAA Calculator, and see how Medicare premiums affect your Social Security deposit with the Social Security COLA Calculator.
Medicare.gov - Avoid Late Enrollment Penalties - Part A (10%, twice the years), Part B (10% for each year) and Part D (1% per month, 63 days) penalty rules; penalties are added to the premium and usually last a lifetime.
Disclaimer: This calculator provides estimates for educational purposes only and does not constitute tax, legal, or financial advice. It applies the Medicare late enrollment penalty formulas to the months and premiums you enter: the Part B standard premium increased 10% for each full 12 months late and rounded to the nearest 10 cents, 1% of the Part D national base beneficiary premium ($38.99 for 2026, $41.33 for 2027) per uncovered month rounded to the nearest $0.10, and a 10% Part A increase for twice the years late. It does not determine which months count, apply the under-65 disability rollback, Medicare Savings Program or state buy-in rules, or predict future premiums. The 2027 Part A and Part B premiums had not been published by CMS as of October 25, 2026. Your penalty determination from the Social Security Administration or your Medicare drug plan controls.