Missing the Medicare Initial Enrollment Period is one of the most common and most expensive coverage errors in the United States, and the damage is fixable but not reversible. The Initial Enrollment Period is the 7-month window around your 65th birthday, and Original Medicare does not enroll you automatically unless you already collect Social Security or Railroad Retirement benefits. If you skipped Part B without qualifying employer coverage, the 2026 late enrollment penalty adds 10% of the $202.90 standard Part B premium for every full 12-month period you were eligible but not enrolled. That surcharge is charged every month for as long as you have Part B. Part D has its own lifetime penalty, and Medigap insurers in most states can deny you or charge more once your guaranteed-issue window closes. The good news is that Medicare offers a formal second chance, the General Enrollment Period, every year from January 1 to March 31, and coverage now starts the first day of the month after you sign up. This page shows exactly how to calculate what you owe, which exceptions can erase the penalty, and the order of steps that protects you from stacking more penalties in 2026 and 2027.
Medicare late penalties come in three separate forms, and mixing them up leads to bad decisions. Part B carries a 10% per year penalty on the 2026 premium. Part D carries a 1% per month penalty based on the $38.99 national base beneficiary premium for 2026. Part A is premium-free for anyone with 40 work credits, so most people owe no Part A penalty at all; only people who must buy Part A, at $311 or $565 per month in 2026, face a 10% surcharge. Federal rules also give several groups a way out. A person who was covered by a group health plan from current work, either their own or a spouse's, at an employer with 20 or more employees, qualifies for an 8-month Special Enrollment Period with no Part B penalty. Low-income enrollees can ask a state Medicaid office, such as Medi-Cal in California or MassHealth in Massachusetts, to pay the Part B premium through a Medicare Savings Program. Read the sections below in order, because the Special Enrollment Period test comes before any penalty math.
6 Steps to Get Coverage
Common Mistakes That Cost People Thousands
Most people who miss the Medicare Initial Enrollment Period make one of five avoidable errors in 2026, and every one of them adds cost:
- Waiting for the next Open Enrollment in the fall. Medicare's October 15 to December 7 window is for changing plans, not for adding Part B, so Part B waits until the General Enrollment Period, January 1 to March 31, 2027.
- Assuming COBRA or retiree coverage counts. Neither stops the Part B penalty clock, and only active group coverage from current work at a 20-plus employee employer earns an 8-month Special Enrollment Period.
- Keeping a Marketplace plan with subsidies after Medicare eligibility. Premium tax credits end when you qualify for premium-free Part A, so you may owe repayment on Form 8962 after your 1095-A arrives.
- Ignoring Part D once Part B is fixed. Every month without creditable drug coverage adds 1% of the $38.99 2026 base premium to a lifetime penalty, even if you take no prescriptions today.
- Skipping the Medicare Savings Program screening. Enrollees under about 135% of the federal poverty level in 2026 can have their Part B premium paid by their state, which can remove most of the penalty cost.
How the 2026 Part B, Part D, and Part A Late Penalties Are Calculated
Part B penalties in 2026 equal 10% of the $202.90 standard premium for each full 12-month period you could have had Part B but did not, and Medicare rounds the result to the nearest $0.10. Only full 12-month periods count, so waiting 23 months is charged as one period, or 10%, while 24 months is charged as two periods, or 20%. The surcharge is added to your monthly premium for as long as you have Part B, and it rises whenever the standard premium rises. A person who waited 24 months pays about $40.60 more per month in 2026, which is roughly $487 more per year. Part D works differently: Medicare multiplies 1% by the number of full months you went without creditable drug coverage after your Initial Enrollment Period, then multiplies by the $38.99 national base beneficiary premium for 2026. Twenty-four uncovered months means 24%, or about $9.40 per month. Part A is premium-free for people with 40 work credits, so no penalty applies there.
Part A penalties apply only to people who must pay for Part A, which costs $311 per month in 2026 with 30 to 39 work credits and $565 per month with fewer than 30 credits. Those buyers who enroll late pay a 10% surcharge on the premium for twice the number of years they were eligible but not enrolled. Retroactive coverage is limited: premium-free Part A can reach back up to 6 months from your application date but never before your eligibility date, while Part B started through the General Enrollment Period begins the first day of the month after you sign up, with no back-dating. Some enrollees also qualify for equitable relief, which can waive or reduce penalties when federal employees or agents gave wrong enrollment advice. Ask Social Security about equitable relief in writing if a Medicare or SSA representative told you not to enroll.
Part B late enrollment penalty by years of delay, 2026 standard premium of $202.90| Full years late | Penalty percent | Extra per month (2026) | Total Part B per month (2026) |
|---|
| 1 | 10% | $20.30 | $223.20 |
| 2 | 20% | $40.60 | $243.50 |
| 3 | 30% | $60.90 | $263.80 |
| 4 | 40% | $81.20 | $284.10 |
| 10 | 100% | $202.90 | $405.80 |
Penalty amounts use the 2026 standard premium and are rounded to the nearest $0.10. The penalty is recalculated each year as the premium changes and does not expire.
Source: Medicare.gov late enrollment penalties; CMS 2026 Medicare Parts A and B premiums fact sheet
Documents Medicare Needs When You Missed the Initial Enrollment Period
Form CMS-40B is the Part B application, and Social Security uses it for every General Enrollment Period request, so you can submit it online at ssa.gov without mailing paper. Form CMS-L564 is the second document, and it matters only if you claim an 8-month Special Enrollment Period, because it lets your employer certify that you had group health coverage from current work and the dates that coverage was active. Without that signed form, Social Security treats you as a General Enrollment Period applicant and charges the 10% per year penalty, so gather the form before you apply rather than after. Proof of age, usually a birth certificate or passport, and your Social Security number complete the file. Payroll records or a benefits letter help if HR is slow. Ask Social Security to record your enrollment in the correct period, because a wrongly coded application is the most common reason penalties are overcharged and later disputed.
Medicaid and Medicare Savings Programs Can Pay the Part B Premium in 2026
Medicare Savings Programs are run by state Medicaid agencies and can cover the Part B premium, including in many cases the surcharge, for enrollees with limited income. Federal income tiers in 2026 are about 100% of the federal poverty level, $15,960 for one person, for QMB, about 120%, $19,152, for SLMB, and about 135%, $21,546, for QI, with asset limits and some states going higher. State Medicaid programs go by different names: California's Medi-Cal, Massachusetts's MassHealth, Arizona's AHCCCS, Tennessee's TennCare, and New Jersey's NJ FamilyCare. Applying does not require waiting for the General Enrollment Period in many states, because state buy-in agreements can enroll qualifying people in Part B outside the usual windows. Check your Medicaid income limits and the federal poverty level table first, then apply at your state Medicaid agency or through healthcare.gov, which routes Medicaid applications to your state. Medicaid enrollment is year-round, so no deadline applies to the application itself.
Frequently Asked Questions
What is the enrollment window after I miss my Medicare Initial Enrollment Period?
The General Enrollment Period runs January 1 through March 31 every year, so the next window is January 1 to March 31, 2027. Since 2023, Part B coverage starts the first day of the month after you sign up, so enrolling on February 10, 2027 starts coverage March 1, 2027. If you had active employer group coverage instead, your Special Enrollment Period lasts 8 months after that employment or coverage ends, and you owe no Part B penalty. Part D enrollment happens separately, during the October 15 to December 7 Annual Election Period.
How do I document my situation when I apply late for Medicare?
Submit Form CMS-40B at ssa.gov for Part B in every case. If you claim a Special Enrollment Period, add Form CMS-L564, which your employer completes to confirm you had group health coverage from current work and the dates it was active. Include proof of age and your Social Security number. Keep payroll records or a benefits letter as backup in case the Social Security office asks for more. Without CMS-L564, Social Security places you in the General Enrollment Period and applies the 10% per year penalty in 2026.
What if I miss the General Enrollment Period too?
Missing the January 1 to March 31, 2027 window means waiting until the next General Enrollment Period, January 1 to March 31, 2028, with no Part B coverage in between. Each additional full 12 months adds another 10% of the standard premium to your penalty, and you also risk a Part D penalty and losing your Medigap guaranteed-issue window. Any active employer coverage or a Medicare Savings Program through your state Medicaid agency can still provide a separate route, so check both before waiting a full year.
Can I get retroactive Medicare coverage after enrolling late?
Premium-free Part A can be retroactive up to 6 months from your application date, but never earlier than the month you became eligible. Part B has no retroactive coverage when you enroll in the General Enrollment Period, and coverage begins the first day of the month after you sign up. Medicare Advantage and Part D also start on the effective date of your election. Enroll early in the January 1 to March 31, 2027 window to shorten the gap and avoid paying for uncovered care yourself.
What is the difference between COBRA and Marketplace coverage and Medicare when I enroll late?
COBRA lets you keep a former employer plan for up to 18 to 36 months at 102% of the full premium, and Marketplace plans through healthcare.gov offer subsidies based on income. Neither counts as active employer coverage, so neither stops the Part B penalty clock. Premium tax credits also end once you are eligible for premium-free Part A. Drop COBRA or the Marketplace plan the day before Part B starts, and keep your Form 1095-A to reconcile credits on your 2026 tax return.
What state-specific rules apply to Medicare late enrollment penalties?
Federal law sets the Part B and Part D penalties, so they do not vary by state. State rules matter for Medicare Savings Programs, which are administered by state Medicaid agencies such as Medi-Cal in California, MassHealth in Massachusetts, AHCCCS in Arizona, and TennCare in Tennessee. Income and asset limits differ by state, and some states have higher limits than the federal 2026 tiers of about 100%, 120%, and 135% of the federal poverty level. Medigap rules also vary, because a few states, such as New York and Connecticut, offer year-round guaranteed issue.
Do I qualify for Medicaid or a Medicare Savings Program after missing my Medicare window?
You may qualify if your 2026 income is under about 135% of the federal poverty level, roughly $21,546 for one person and about $29,000 for two, and your assets fit your state's limits. The Medicare Savings Program can pay your Part B premium, and in many cases can address the surcharge, while Extra Help lowers drug costs. Apply through your state Medicaid agency, which is open year-round, and confirm in writing whether your penalty is covered before you sign up.
How much are the Part B and Part D penalties in 2026?
The Part B penalty is 10% of the $202.90 standard premium for every full 12 months you waited, so two years late adds about $40.60 per month in 2026 and lasts for life. The Part D penalty is 1% of the $38.99 national base premium for every month without creditable drug coverage, so 24 months adds about $9.40 per month. Part A is premium-free for most people with 40 work credits, so no Part A penalty applies unless you must buy Part A at $311 or $565 per month in 2026.
