Medicare Enrollment and Late-Enrollment Penalties (2026)

Medicare’s three late-enrollment penalties are built on three different formulas, and only one of them ends. The Part B penalty adds 10 percent of the standard premium for each full 12-month period a person could have enrolled but did not, and it generally lasts for as long as the person keeps Part B (Source: Medicare.gov, “Avoid late enrollment penalties,” 2026). Applied to the 2026 standard Part B premium of $202.90 per month, a two-year delay produces a 20 percent surcharge and a monthly premium of $243.50 (base premium Source: CMS, “2026 Medicare Parts A and B Premiums and Deductibles” fact sheet, released November 14, 2025; penalty computation follows 42 U.S.C. 1395r(b)-(c)).

Why enrollment timing drives the penalties

Medicare’s late-enrollment penalties are not fines assessed after the fact. They are premium surcharges written into federal law and regulation, and they attach automatically when a person enrolls after a window closes without qualifying protection. Understanding the timing rules is therefore the first step in understanding the penalties, because every penalty is measured from the moment an enrollment window ends.

There are three principal windows. The Initial Enrollment Period (IEP) runs seven months: the three months before the month a person turns 65, the birthday month itself, and the three months after (Source: Medicare.gov, “When can I sign up for Medicare?”, 2026). If a person qualifies for premium-free Part A, that Part A coverage starts the month they turn 65, and coverage always begins on the first of a month (Source: Medicare.gov, “When does Medicare coverage start?”, 2026).

The General Enrollment Period (GEP) runs every year from January 1 through March 31, and it exists for people who did not sign up for Part A or Part B when first eligible. Coverage under a GEP sign-up starts the first day of the month after enrollment (Source: Medicare.gov, “When can I sign up for Medicare?”; Medicare.gov, “When does Medicare coverage start?”).

The Special Enrollment Period (SEP) is the mechanism that lets many people avoid a penalty entirely. For a person working past 65 with employer group health coverage based on current employment, the Part B SEP runs eight months. That eight-month window starts when the employment ends or when the employer group health coverage ends, whichever happens first, and a person who enrolls within it does not pay a Part B late-enrollment penalty (Source: Medicare.gov, “Working past 65”, 2026). A frequent point of confusion: electing COBRA does not extend the SEP, because the eight-month clock starts even if a person takes COBRA or other non-Medicare coverage (Source: Medicare.gov, “Working past 65”). For a deeper look at how Medicare costs fit into a full retirement picture, see the companion briefing on Medicare cost in retirement 2026.

Part B late-enrollment penalty: 10 percent per full year, for life

The Part B penalty is the one most people encounter, because Part B (unlike premium-free Part A) carries a monthly premium for nearly every beneficiary. The statute is explicit. Under 42 U.S.C. 1395r(b), the monthly premium “shall be increased by 10 percent of the monthly premium so determined for each full 12 months” a person could have been enrolled but was not (Source: Cornell Legal Information Institute, 42 U.S.C. 1395r). Medicare.gov states the same rule in plain language and gives its own example: waiting two full years produces a 20 percent penalty (Source: Medicare.gov, “Avoid late enrollment penalties”, 2026).

Three features of the formula matter for accuracy. First, the penalty accrues only for full 12-month periods. A delay of 18 months counts as one 12-month period, or 10 percent, not 15 percent, so the percentage is always a multiple of 10 (Source: Medicare.gov, “Avoid late enrollment penalties”; 42 U.S.C. 1395r(b)). Second, the rounding rule in 42 U.S.C. 1395r(c) requires that a premium not already a multiple of 10 cents be rounded to the nearest 10 cents, and that rounding applies to the final penalty-inclusive premium, not to the penalty portion alone (Source: Cornell Legal Information Institute, 42 U.S.C. 1395r). Third, the penalty is calculated on the standard premium; the statute directs that it be figured “without regard to any adjustment under subsection (i),” meaning income-related monthly adjustment amounts (IRMAA) are excluded from the penalty base (Source: Cornell Legal Information Institute, 42 U.S.C. 1395r). Readers whose income triggers IRMAA can review the separate Medicare IRMAA 2026 brackets and premiums briefing.

The table below applies the formula to the 2026 standard Part B premium of $202.90. The base premium is Tier-1 primary (Source: CMS 2026 Parts A and B fact sheet, Nov 14, 2025); the arithmetic follows 42 U.S.C. 1395r(b)-(c).

The two-year, 20 percent case at $243.50 matches Medicare.gov’s own worked example applied to the 2026 base. One note on citation accuracy: the seven-year figure is $344.90 after statutory rounding to the nearest 10 cents, not the un-rounded $344.93 that circulates in some industry write-ups (Source: 42 U.S.C. 1395r(c); un-rounded figure noted in a SeniorSimple industry example).

Illustrating the multi-year arithmetic

Because the Part B penalty generally lasts as long as a person keeps Part B, the annual surcharge repeats. The table below multiplies the 2026 added-per-month figure across illustrative horizons. These are arithmetic illustrations that hold the 2026 base constant; they are not projections, and they are not life-expectancy claims.

In practice the Part B standard premium rises in most years, so the true dollar cost of a delay would be higher than these constant-2026 illustrations show.

Part D late-enrollment penalty: 1 percent per month, recalculated yearly

The Part D penalty uses a different clock. It is calculated as 1 percent of the “national base beneficiary premium” multiplied by the number of full uncovered months a person was eligible for Medicare drug coverage but had neither Part D nor other creditable prescription drug coverage. The result is rounded to the nearest $0.10 and added to the monthly premium, generally for as long as the person has Part D (Source: Medicare.gov, “Medicare drug coverage (Part D) late enrollment penalty”, 2026; Medicare.gov, “Avoid late enrollment penalties”).

For 2026 the national base beneficiary premium is $38.99 per month (Source: CMS “2026 Medicare Part D Bid Information and Part D Premium Stabilization Demonstration Parameters” fact sheet, released July 28, 2025; also stated on the Medicare.gov Part D penalty page). That is a $2.21 increase, about 6 percent, over the 2025 figure of $36.78 (Source: CMS 2026 Part D Bid Information fact sheet). The 6 percent step is not a coincidence: the Inflation Reduction Act caps the annual increase in the Part D base beneficiary premium at 6 percent per year for 2024 through 2029 (Source: CMS 2026 Part D Bid Information fact sheet).

The uncovered-month trigger is statutory. Under 42 CFR 423.46, the penalty applies if there is a continuous period of 63 days or more, at any time after the end of the person’s Part D Initial Enrollment Period, during which the person was eligible to enroll in a Part D plan, was not enrolled, and was not covered by any creditable prescription drug coverage (Source: 42 CFR 423.46, verified via Cornell Legal Information Institute). Creditable coverage, the coverage that keeps the clock from running, is coverage expected to pay on average at least as much as Medicare’s standard Part D benefit, and it includes qualifying employer or union group coverage, retiree plans, VA and TRICARE and other military coverage, qualified State Pharmaceutical Assistance Programs, and certain Medigap drug coverage (Source: Medicare.gov, “Creditable prescription drug coverage”, 2026). People who receive Extra Help, the low-income subsidy, do not pay the Part D penalty (Source: Medicare.gov, “Creditable prescription drug coverage”).

The table below applies the 2026 formula. The 14-month and 43-month rows match the illustrations used by Medicare.gov and the National Council on Aging (Source: Medicare.gov Part D penalty page; NCOA, “Medicare Part D Late Enrollment Penalty”, using the 2026 $38.99 figure).

One structural detail sets Part D apart from Part B: because the national base beneficiary premium changes each year, the Part D penalty dollar amount is recalculated annually even though the percentage stays locked to the number of uncovered months (Source: Medicare.gov, “Avoid late enrollment penalties”; CMS, “Creditable Coverage and Late Enrollment Penalty”). A beneficiary who disputes a penalty may request reconsideration through an Independent Review Entity contracted by CMS (Source: 42 CFR 423.46; CMS, “Late Enrollment Penalty (LEP) Appeals”).

Context: the 2026 Part D premium environment

The 2026 national average monthly bid amount is reported at $239.27, an increase of about 33 percent from 2025 (Source: CMS 2026 Part D Bid Information fact sheet, Jul 28, 2025). The maximum Part D plan deductible for 2026 is $615, and some plans set a $0 deductible (Source: CMS 2026 Part D Bid Information fact sheet). Under the voluntary 2026 Part D Premium Stabilization Demonstration, CMS reduced the uniform base beneficiary premium reduction from $15 to $10 and raised the year-over-year total Part D premium increase limit from $35 to $50 (Source: CMS 2026 Part D Bid Information fact sheet).

Part A late-enrollment penalty: flat 10 percent, but not for life

The Part A penalty is structurally different from the other two, and it affects a small share of beneficiaries. About 99 percent of Medicare beneficiaries pay no Part A premium, because they or a spouse have at least 40 quarters, or 10 years, of Medicare-covered employment as determined by the Social Security Administration (Source: CMS 2026 Parts A and B fact sheet, Nov 14, 2025). The Part A late penalty therefore applies only to the roughly 1 percent who must buy Part A.

For those who must buy Part A and do not do so when first eligible, the monthly Part A premium may go up 10 percent. Unlike Part B and Part D, this is not a lifetime surcharge. A person pays the higher premium for twice the number of years they did not sign up. Medicare.gov’s own example: a person eligible for Part A for two years who did not sign up pays the higher premium for four years (Source: Medicare.gov, “Avoid late enrollment penalties”, 2026). The surcharge is a flat 10 percent, not a per-year compounding figure like Part B.

The 2026 Part A premiums the surcharge attaches to are $565 per month for those with fewer than 30 quarters of coverage, up $47 from $518 in 2025, and $311 per month for those with 30 to 39 quarters, up $26 from $285 in 2025 (Source: CMS 2026 Parts A and B fact sheet; corroborated by Center for Medicare Advocacy). The table below illustrates the flat 10 percent surcharge and the time-limited total.

Other 2026 Part A cost figures

For context, the 2026 Part A inpatient hospital deductible is $1,736 per benefit period, up $60 from $1,676 in 2025 (Source: CMS 2026 Parts A and B fact sheet). Daily hospital coinsurance for days 61 through 90 is $434 in 2026, lifetime reserve day coinsurance is $868 per day (maximum 60 reserve days over a lifetime), and skilled nursing facility coinsurance for days 21 through 100 is $217 per day, with $0 for days 1 through 20 (Source: CMS 2026 Parts A and B fact sheet; CMS MLN Matters MM14279, “Medicare Deductible, Coinsurance and Premium Rates: CY 2026 Update”).

How the three penalties compare

The three penalties differ on rate, base, and duration. The comparison below summarizes the structural distinctions that determine how much each one ultimately costs.

Sources: Medicare.gov, “Avoid late enrollment penalties”; 42 U.S.C. 1395r; 42 CFR 423.46; CMS 2026 fact sheets (2025-2026).

Frequently asked questions

How long is the Medicare Initial Enrollment Period?

It is seven months: the three months before the month a person turns 65, the birthday month, and the three months after (Source: Medicare.gov, “When can I sign up for Medicare?”, 2026).

When is the General Enrollment Period?

January 1 through March 31 each year, for people who did not sign up for Part A or Part B when first eligible. Coverage starts the first day of the month after sign-up (Source: Medicare.gov, “When can I sign up for Medicare?”, 2026).

How long is the Part B Special Enrollment Period for people working past 65?

Eight months, starting when the employment ends or when the employer group health coverage ends, whichever comes first (Source: Medicare.gov, “Working past 65”, 2026).

Does electing COBRA extend the Part B Special Enrollment Period?

No. The eight-month clock starts even if a person takes COBRA or other non-Medicare coverage; COBRA does not extend the SEP (Source: Medicare.gov, “Working past 65”, 2026).

What is the Part B late-enrollment penalty rate?

10 percent of the standard Part B premium for each full 12-month period a person could have had Part B but did not sign up (Source: Medicare.gov, “Avoid late enrollment penalties”, 2026).

How long does the Part B penalty last?

It generally lasts for as long as a person keeps Part B (Source: Medicare.gov, “Avoid late enrollment penalties”; 42 U.S.C. 1395r(b)).

What is the 2026 standard Part B premium?

$202.90 per month, an increase of $17.90 from $185.00 in 2025 (Source: CMS 2026 Parts A and B Premiums and Deductibles fact sheet, Nov 14, 2025).

What would a two-year Part B delay cost in 2026?

A 20 percent penalty, producing a monthly premium of $243.50, about $40.60 more per month or roughly $487 more per year (base Source: CMS 2026 fact sheet; computation follows 42 U.S.C. 1395r(b)-(c)).

Does a partial year of Part B delay add a partial penalty?

No. Only full 12-month periods count, so an 18-month delay is one 12-month period, or 10 percent, not 15 percent (Source: Medicare.gov, “Avoid late enrollment penalties”; 42 U.S.C. 1395r(b)).

Is the Part B penalty calculated on the IRMAA-adjusted premium?

No. The statute directs that the penalty be figured on the standard premium without regard to the income-related adjustment (Source: 42 U.S.C. 1395r(b), via Cornell Legal Information Institute). See the Medicare IRMAA 2026 brackets briefing for the separate income surcharge.

What is the Part D late-enrollment penalty formula?

1 percent of the national base beneficiary premium multiplied by the number of full uncovered months, rounded to the nearest $0.10 and added to the monthly premium (Source: Medicare.gov, “Medicare drug coverage (Part D) late enrollment penalty”, 2026).

What is the 2026 Part D national base beneficiary premium?

$38.99 per month, about a 6 percent increase over the 2025 figure of $36.78 (Source: CMS 2026 Medicare Part D Bid Information fact sheet, Jul 28, 2025).

What triggers the Part D penalty?

A continuous period of 63 days or more, after the Part D Initial Enrollment Period, without Part D or other creditable drug coverage (Source: 42 CFR 423.46).

What counts as creditable prescription drug coverage?

Coverage expected to pay on average at least as much as Medicare’s standard Part D benefit, including qualifying employer or union coverage, retiree plans, VA and TRICARE coverage, qualified State Pharmaceutical Assistance Programs, and certain Medigap drug coverage (Source: Medicare.gov, “Creditable prescription drug coverage”, 2026).

Do people with Extra Help pay the Part D penalty?

No. People who receive Extra Help, the low-income subsidy, do not pay the Part D late-enrollment penalty (Source: Medicare.gov, “Creditable prescription drug coverage”, 2026).

Does the Part D penalty change from year to year?

Yes. Because the national base beneficiary premium changes annually, the dollar penalty is recalculated each year, though the percentage stays tied to the number of uncovered months (Source: Medicare.gov, “Avoid late enrollment penalties”; CMS, “Creditable Coverage and Late Enrollment Penalty”).

Can a Part D penalty be appealed?

Yes. A beneficiary charged a penalty may request reconsideration through an Independent Review Entity contracted by CMS (Source: 42 CFR 423.46; CMS, “Late Enrollment Penalty (LEP) Appeals”).

Who pays a Part A premium?

About 1 percent of beneficiaries. Roughly 99 percent pay no Part A premium because they or a spouse have at least 40 quarters of Medicare-covered employment (Source: CMS 2026 Parts A and B fact sheet).

How does the Part A late penalty work?

For those who must buy Part A and delay, the premium may go up a flat 10 percent, paid for twice the number of years of delay, then it ends (Source: Medicare.gov, “Avoid late enrollment penalties”, 2026).

What are the 2026 Part A premiums?

$565 per month for those with fewer than 30 quarters of coverage and $311 per month for those with 30 to 39 quarters (Source: CMS 2026 Parts A and B fact sheet).

What is the 2026 Part A inpatient hospital deductible?

$1,736 per benefit period, up $60 from $1,676 in 2025 (Source: CMS 2026 Parts A and B fact sheet).

How is the Part A penalty different from the Part B and Part D penalties?

The Part A penalty is a flat 10 percent regardless of delay length and is time-limited to twice the years of delay, while the Part B and Part D penalties scale with the length of the delay and generally last for life (Source: Medicare.gov, “Avoid late enrollment penalties”; 42 U.S.C. 1395r; 42 CFR 423.46).

Where can I read more about Medicare income surcharges and Social Security taxation?

See the related briefings on Medicare IRMAA 2026 brackets and premiums and taxation of Social Security benefits 2026 for adjacent 2026 figures.

Sources

CMS, “2026 Medicare Parts A and B Premiums and Deductibles” fact sheet (released November 14, 2025), https://www.cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles.
CMS, “2026 Medicare Part D Bid Information and Part D Premium Stabilization Demonstration Parameters” fact sheet (released July 28, 2025), https://www.cms.gov/newsroom/fact-sheets/2026-medicare-part-d-bid-information-and-part-d-premium-stabilization-demonstration-parameters.
CMS, July 28, 2025 Parts C and D Announcement, https://www.cms.gov/files/document/july-28-2025-parts-c-d-announcement.pdf.
CMS MLN Matters MM14279, “Medicare Deductible, Coinsurance and Premium Rates: CY 2026 Update,” https://www.cms.gov/files/document/mm14279-medicare-deductible-coinsurance-premium-rates-cy-2026-update.pdf.
CMS, “Creditable Coverage and Late Enrollment Penalty,” https://www.cms.gov/medicare/enrollment-renewal/part-d-plans/creditable-coverage-and-late-enrollment-penalty.
CMS, “Late Enrollment Penalty (LEP) Appeals,” https://www.cms.gov/medicare/appeals-grievances/prescription-drug/late-enrollment-penalty-appeals.
Medicare.gov, “When can I sign up for Medicare?” https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-can-i-sign-up-for-medicare.
Medicare.gov, “When does Medicare coverage start?” https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start.
Medicare.gov, “Working past 65,” https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/working-past-65.
Medicare.gov, “Avoid late enrollment penalties,” https://www.medicare.gov/basics/costs/medicare-costs/avoid-penalties.
Medicare.gov, “Medicare drug coverage (Part D) late enrollment penalty,” https://www.medicare.gov/drug-coverage-part-d/costs-for-medicare-drug-coverage/part-d-late-enrollment-penalty.
Medicare.gov, “Creditable prescription drug coverage,” https://www.medicare.gov/health-drug-plans/part-d/basics/creditable-coverage.
Cornell Legal Information Institute, 42 U.S.C. 1395r, https://www.law.cornell.edu/uscode/text/42/1395r.
Cornell Legal Information Institute, 42 CFR 423.46, https://www.law.cornell.edu/cfr/text/42/423.46.
Center for Medicare Advocacy, “2026 Medicare Rates,” https://medicareadvocacy.org/2026-medicare-rates/.
National Council on Aging, “Medicare Part D Late Enrollment Penalty,” https://www.ncoa.org/article/medicare-part-d-late-enrollment-penalty/.

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