Medicare Late Enrollment Penalty 2026: Part B and Part D Cost

The two penalties side by side

Medicare has three late enrollment penalties. Part A applies only to people who must buy it, and Medicare.gov says the premium may go up 10% for twice the number of years they did not sign up. This page covers the two that most retirees meet: Part B (doctor and outpatient care) and Part D (drug coverage). They work differently, and the differences decide the dollars.

Source: 42 CFR 408.22, 423.46 and 423.286 (eCFR, version of October 1, 2026); Medicare.gov “Avoid late enrollment penalties” and “Part D late enrollment penalty”; CMS fact sheet of November 14, 2025; CMS memo of July 28, 2025. “Penalty step” for Part D is our arithmetic: 1% of $38.99 is $0.3899.

The regulation behind Part D says the penalty is the greater of an amount CMS finds actuarially sound or 1% of the base beneficiary premium per uncovered month (42 CFR 423.286(d)(3)(i)). The published practice, on Medicare.gov, is the 1% formula.

Part B: what each stretch of delay costs

The clock is simple. The Initial Enrollment Period lasts 7 months, from 3 months before the month you turn 65 to 3 months after it (Medicare.gov). After it ends you can enroll between January 1 and March 31 each year in the General Enrollment Period, and coverage then starts the month after you sign up. The regulation counts the months between the close of the Initial Enrollment Period and the close of the month you first enrolled, and from 2023 it excludes months of non-coverage when you used an exceptional-conditions Special Enrollment Period in time (42 CFR 408.24(b)). Then 408.22 turns every full 12 months into 10%. Medicare.gov puts it this way: “You’ll pay an extra 10% for each year you could have signed up for Part B, but didn’t.”

Source: 42 CFR 408.22; CMS fact sheet, November 14, 2025 ($202.90); Medicare.gov rounding rule. Dollar columns are our arithmetic: $202.90 x (1 + 10% per full year), rounded to the nearest $0.10 as in the Medicare.gov example, penalty part = rounded premium minus $202.90.

The edge is sharp at 12 months. A person who is 11 months late pays no penalty; one who is 12 months late pays $20.30 a month more for the rest of the Part B life. Because the penalty is a percentage of each year's standard premium, it will climb when the premium does: the standard premium rose $17.90, from $185.00 in 2025 to $202.90 in 2026 (CMS), and a 20% penalty rose with it (our arithmetic).

Part B lifetime cost, and the ten-year line

People often hear “a penalty for life” without a number. Here it is at flat 2026 prices, assuming the Initial Enrollment Period ends at about age 65 and 3 months and the person stays enrolled to the stated age. Real premiums have been rising, so these figures are low (our arithmetic).

Our arithmetic from the 2026 standard premium of $202.90 (CMS) and the 10% rule (42 CFR 408.22): months paid = months from about age 65 and 3 months to the target age, minus the months late. “Premiums not paid” = months late x $202.90.

The right-hand column is the same in every row. Skipping a year of Part B saves $2,434.80 at $202.90 a month; the penalty for that year costs $243.60 a year; the two are equal after 9.995 years (our arithmetic). The figure is an arithmetic fact about the 10% rule, not a recommendation: it counts only premiums, not the claims that Part B would have paid in those years, and it assumes you had no other coverage. Anyone who delays because they or a spouse are still working with employer coverage is in a different position, because the Special Enrollment Period can remove the penalty.

Part D: what each uncovered month costs

Part D is smaller per month and larger in count, because the clock runs per month. The gap must be a continuous 63 days or longer to start the penalty (42 CFR 423.46(a)); the penalty is then 1% of the base beneficiary premium for each uncovered month. Medicare.gov gives the rule and a worked case: 14 uncovered months is a 14% penalty on $38.99, $5.46, shown as $5.50 after rounding.

Source: 42 CFR 423.286(d)(3); CMS memos of July 28, 2025 (2026 base premium $38.99) and July 28, 2026 (2027 base premium $41.33); Medicare.gov rounding to the nearest $0.10. Dollar columns are our arithmetic. The 2027 column applies the same months to the 2027 base premium; your plan notifies you of the amount it actually charges.

The 2027 base premium is $38.99 x 1.06 = $41.33; the CMS memo shows that calculation, and the Inflation Reduction Act caps its yearly rise at 6% for 2024 through 2029. The penalty is added to your plan premium, so it travels with you when you change plans. At flat 2026 prices, 24 uncovered months cost $2,002.20 to age 85 and $2,566.20 to age 90; 60 months cost $4,141.80 and $5,545.80 (our arithmetic, same age assumption as above).

The penalty and IRMAA: a stack, not a multiple

Readers with taxable rental, REIT or K-1 income are the ones most likely to be in an IRMAA tier as well. Our IRMAA guide has the tiers and the two-year MAGI look-back. The question here is whether the two charges compound. On the text we saved, they do not. The Part B penalty is defined as an increase of “the standard monthly premium determined under § 408.20”, so the 10% steps are taken on $202.90, not on a surcharged premium. Medicare.gov's own example adds the penalty to the standard premium and notes separately that “You may also pay a higher premium depending on your income.” The Part D penalty is a share of the base beneficiary premium, and CMS says the Part D income-related amount is paid “in addition to their Part D premium.” The Part B penalty is 10 percent of the standard premium alone, so it does not rise with IRMAA.

Worked example (our arithmetic): one person who enrolled 24 months late in both Part B and Part D. Penalties are $40.60 plus $9.40, or $50.00 a month, $600.00 a year, at every income level. The IRMAA is the 2026 CMS amount for the tier, Part B surcharge plus Part D surcharge.

Source: CMS “2026 Medicare Parts A & B Premiums and Deductibles” fact sheet, November 14, 2025 (Part B surcharges $81.20, $202.90, $324.60, $446.30, $487.00; Part D surcharges $14.50, $37.50, $60.40, $83.30, $91.00). Sums are our arithmetic. Your Part D plan premium and any Part B or Part D deductibles are not included.

For a couple, double it: two people each 36 months late on both parts pay $74.90 a month each ($60.90 for Part B plus $14.00 for Part D), $1,797.60 a year together, which is less than the $2,296.80 that a joint couple pays in tier 1 IRMAA alone (our arithmetic; the tier 1 couple figure is the one in our IRMAA guide). IRMAA moves with the income on your return, such as a property sale; the penalty does not. A Form SSA-44 request (guide) addresses IRMAA, not the late enrollment penalty.

Ways the penalty is avoided or removed

• Part B and work coverage. Medicare.gov says a Special Enrollment Period starts the first month after the Initial Enrollment Period ends and ends 8 months after the group health plan coverage or the employment ends, whichever happens first, and that COBRA is not group health plan coverage and does not change when it ends. For people 65 or over the coverage must be by reason of the current employment status of you or your spouse (42 CFR 407.20(c)), and Medicare.gov lists “Your COBRA coverage or retiree coverage ends” and having or losing Marketplace coverage among the situations that do not qualify for a Special Enrollment Period. Medicare.gov also says you generally will not pay a Part B penalty if you qualify for a Special Enrollment Period or enroll in a Medicare Savings Program.
• Part D and “creditable” coverage. No penalty if the gap is shorter than 63 days or the coverage in the gap was creditable, that is, similar in value to Part D (Medicare.gov). Medicare.gov says people who get Extra Help do not pay the Part D penalty.
• If you hold an HSA. Our HSA and Medicare guide covers the six-month look-back on Part A and the contribution cut-off; check there how the dates interact with your enrollment.
• If the plan gets the months wrong. For Part D, 42 CFR 423.46(c) allows a request for reconsideration, reviewed by CMS or an independent review entity, and says those decisions are not subject to appeal.
• Choosing the plan after enrolling. Our Medigap and Medicare Advantage comparison covers the plan choice; it does not change the penalty, which follows you.

What a reader can do with this

• Count your own months first. Part B months run from the end of your Initial Enrollment Period, not from age 65, and a gap shorter than 12 months costs nothing on Part B. Part D months run from the end of your Initial Enrollment Period too, but a gap under 63 days costs nothing.
• Find out whether your delay was covered by a Special Enrollment Period before you accept a penalty. Employer coverage from your own or your spouse's current work is the common case; retiree-only coverage and COBRA are not.
• Check the Part D notice. The plan tells you whether there is a penalty and what the premium will be (Medicare.gov); if you had coverage you think was creditable, ask for a reconsideration.
• Add the penalty to the IRMAA model, not multiply it. The penalty is a fixed amount set by your months of delay ($600.00 a year in the 24-month example); IRMAA changes by tier with your MAGI from two years earlier.
• Re-run this when the 2027 figures come out. CMS has published the 2027 Part D base premium ($41.33) but not the 2027 Part B premium, and the penalty will follow both.

This is analysis of public documents, not investment, legal or tax advice.

FAQ

Sources, read and saved on October 27, 2026: 42 CFR 407.20, 408.20, 408.22, 408.24, 408.25, 423.46 and 423.286 (eCFR, version of October 1, 2026); CMS fact sheet “2026 Medicare Parts A & B Premiums and Deductibles”, November 14, 2025; CMS “Annual Release of Part D National Average Monthly Bid Amount” memos of July 28, 2025 and July 28, 2026 and the 2026 Part D bid information fact sheet; Medicare.gov “Avoid late enrollment penalties”, “Part D late enrollment penalty” and “When does Medicare coverage start?”. Dollar tables, lifetime totals and IRMAA stacks are our arithmetic at flat 2026 prices.