Enrolling in Medicare for the first time

Who this guide is for

You're approaching 65 and need to figure out Medicare, or you've recently become eligible because of a disability. You may have heard of Part A, Part B, Part D, Medicare Advantage, and Medigap, but you're not sure what you actually need, when to sign up, or what happens if you wait too long.

This guide walks through every decision in order, from initial eligibility through choosing supplemental coverage. If you're retiring before 65 and need to bridge the gap between employer coverage and Medicare, see our guide to health insurance when retiring before 65 first. If you're already on Medicare and considering a switch between Original Medicare and Medicare Advantage, start with Original Medicare vs. Medicare Advantage.

Your decision checklist

Am I eligible for Medicare, and when does my enrollment window open?
Do I need to sign up, or am I automatically enrolled?
What does Original Medicare cover, and what are the gaps?
Should I choose Original Medicare + Medigap + Part D, or Medicare Advantage? (This is the central fork in this guide.)
If Original Medicare: which Medigap plan and which Part D plan?
If Medicare Advantage: what should I look for in a plan?
What about dental, vision, and hearing?
What happens to my current coverage?
What are the penalties if I get the timing wrong? (Read this section even if you think the timing doesn't apply to you. The penalties are permanent.)
My action plan and timeline

1. Am I eligible for Medicare, and when does my enrollment window open?

What you're deciding: Whether you can enroll in Medicare and when your window starts.

Eligibility check: You are generally eligible for Medicare if you meet one of these criteria:

Age 65 or older. Most people become eligible at 65 based on their own work history (or a spouse's). If you or your spouse paid Medicare taxes for at least 10 years (40 quarters), you generally qualify for premium-free Part A.
Under 65 with a qualifying disability. If you've received Social Security Disability Insurance (SSDI) for 24 months, you are automatically eligible for Medicare. The 24-month count begins from the first month of disability entitlement, not from your application date.
Any age with End-Stage Renal Disease (ESRD) or ALS. People diagnosed with ESRD or ALS may qualify for Medicare regardless of age, with different timing rules.

This guide focuses primarily on the turning-65 path, which is the most common. If you're eligible due to disability, ESRD, or ALS, the decisions are similar but the enrollment windows differ. Check with Social Security or Medicare directly for your specific timing.

Your Initial Enrollment Period

If you're turning 65, your Initial Enrollment Period (IEP) is a 7-month window: the 3 months before your 65th birthday month, your birthday month, and the 3 months after. This is your primary window to sign up for Part A and Part B without penalties or delays.

When your coverage starts depends on when you sign up within the window:

Sign up during the 3 months before your birthday month: coverage generally starts the first day of your birthday month.
Sign up during your birthday month: coverage generally starts the first day of the following month.
Sign up in the 1-3 months after your birthday month: Part B coverage starts the first day of the month after you sign up, so you could go 2-4 months past your birthday month without Part B. You can still enroll without a penalty during these months.

The earlier you act within your IEP, the sooner your coverage begins. There is no advantage to waiting.

What to watch out for: Your IEP does not repeat. If you miss it and don't have qualifying coverage (like employer coverage through active employment), you may face a permanent penalty and have to wait for the General Enrollment Period (January 1 through March 31 each year). Coverage starts the first day of the month after you sign up, which can still mean a gap of months with no Medicare coverage.

Go deeper: Medicare enrollment periods · What is Medicare?

2. Do I need to sign up, or am I automatically enrolled?

What you're deciding: Whether Medicare enrollment happens on its own or whether you need to take action.

Eligibility check: Whether you're automatically enrolled depends on whether you're already receiving Social Security benefits:

If you're receiving Social Security or Railroad Retirement Board benefits when you turn 65, you are generally enrolled in Part A and Part B automatically. You should receive your Medicare card in the mail about 3 months before your 65th birthday. You don't need to do anything for Parts A and B to start, but you do still need to make decisions about Part D and supplemental coverage.
If you're not receiving Social Security when you turn 65 (for example, you're still working and haven't claimed benefits yet), you are not automatically enrolled. You must actively sign up through Social Security, either online at ssa.gov, by phone, or in person.

What to watch out for: Automatic enrollment in Part B is not always the right move. Part B requires a monthly premium (the standard premium is set annually by CMS; higher earners pay more through IRMAA surcharges). If you or your spouse are still working and have coverage through that job, you may be able to delay Part B without penalty. This works best if the employer has 20 or more employees, because then the job plan pays first; if the employer has fewer than 20 employees, Medicare usually pays first, so the job plan may pay little or nothing unless you also have Part B. Check with the employer's benefits office before delaying. And the rules are specific: COBRA, retiree coverage, and coverage through a former employer generally do not count as creditable coverage that lets you delay Part B penalty-free.

If you are automatically enrolled and want to delay Part B, you can decline it only if you or your spouse are still working and covered by an employer group plan (retiree coverage and COBRA don't count). Follow the instructions that come with your Medicare card and send the card back; you keep Part A. But make sure you understand the rules before opting out, because getting it wrong triggers a permanent penalty.

Go deeper: Do I have to sign up for Medicare? · Medicare and employer coverage

3. What does Original Medicare cover, and what are the gaps?

What you're deciding: Whether Original Medicare alone provides enough coverage, or whether you'll need to add supplemental protection.

Eligibility check: If you are enrolled in Medicare Part A and Part B, you have Original Medicare. This is the foundation that everything else builds on. Understanding what it covers and what it doesn't is essential before choosing supplemental coverage.

What Original Medicare covers

Part A (hospital insurance) covers:

Inpatient hospital stays
Skilled nursing facility care (limited, following a qualifying hospital stay)
Home health care (limited)
Hospice care

Most people pay no premium for Part A if they or their spouse have sufficient work history. However, Part A has a per-benefit-period deductible (set annually by CMS) for each hospital admission.

Part B (medical insurance) covers:

Doctor visits and outpatient care
Preventive services (many at no cost)
Durable medical equipment
Outpatient mental health services
Some home health services

Part B requires a monthly premium and has an annual deductible. After the deductible, you generally pay 20% coinsurance on most Part B services.

The gaps that matter

Original Medicare has significant coverage gaps that many new enrollees don't expect:

No out-of-pocket maximum. Unlike most private insurance, Original Medicare has no annual cap on what you could owe. If you have a serious illness or multiple hospitalizations, your 20% coinsurance on Part B services alone could add up to tens of thousands of dollars.
No prescription drug coverage. Original Medicare does not cover most outpatient prescriptions. You need a separate Part D plan or a Medicare Advantage plan that includes drug coverage.
Limited dental, vision, and hearing coverage. Original Medicare covers very little routine dental, vision, or hearing care. See Decision 7.
No long-term care. Medicare does not pay for custodial or long-term care when that is the only care you need, whether in a nursing home or assisted living. It can cover up to 100 days of skilled nursing facility care after a qualifying 3-day hospital stay.
The 20% coinsurance on Part B has no cap. For expensive procedures, surgeries, or ongoing treatment, 20% of the Medicare-approved amount can be substantial.

Why this matters for your next decision: The gaps in Original Medicare are the reason most people add supplemental coverage, either through a Medicare Supplement (Medigap) plan, a Medicare Advantage plan, or both a Part D plan and other coverage. The next section covers that central choice.

Go deeper: Original Medicare coverage and gaps · Part A · Part B · How much does Medicare cost?

4. Should I choose Original Medicare + Medigap + Part D, or Medicare Advantage?

What you're deciding: Which path to take for your Medicare coverage. This is the most consequential decision in this guide.

Eligibility check: To enroll in a Medicare Supplement (Medigap) plan, you must be enrolled in both Medicare Part A and Part B; a standalone Part D plan requires Part A or Part B. To enroll in a Medicare Advantage plan, you must be enrolled in Part A and Part B and live in the plan's service area. Both paths require the same foundation.

About 70 million people have Medicare (2026). More than half of eligible beneficiaries, about 35 million people, are enrolled in Medicare Advantage, with the rest in traditional (Original) Medicare, according to KFF data. Neither path is universally better. The right choice depends on how you use healthcare, where you live, what you're willing to pay, and how much flexibility matters to you.

The two paths, compared

Path A: Original Medicare + Medigap + standalone Part D

You keep Original Medicare (Parts A and B) as your primary coverage.
You add a Medigap plan to cover some or all of the gaps (deductibles, coinsurance, excess charges).
You add a standalone Part D plan for prescription drug coverage.
You can see any doctor or specialist who accepts Medicare, anywhere in the country, without referrals or prior authorization. This is the biggest practical advantage of this path.
Your costs are more predictable: with a comprehensive Medigap plan (like Plan G), your out-of-pocket costs for Medicare-covered services are low after you pay the Part B deductible ($283 in 2026). You still pay the Medigap premium, a separate Part D premium, and the cost of services Medicare and Medigap don't cover, such as dental, vision, hearing, and long-term care.
You pay more in monthly premiums (Part B + Medigap + Part D), but less when you actually use healthcare.

Path B: Medicare Advantage (Part C)

A private plan replaces Original Medicare for delivering your Part A and Part B benefits. Most plans include Part D drug coverage.
Many plans have $0 or low additional premiums beyond the Part B premium you still pay.
Most plans offer extra benefits like dental, vision, hearing, fitness programs, and over-the-counter allowances.
Plans have an annual out-of-pocket maximum, which Original Medicare does not have.
HMO plans generally require you to use in-network providers except in emergencies; PPO plans let you go out of network at a higher cost. Most plans require referrals for specialists and prior authorization for certain tests, procedures, or medications. If you travel frequently or see doctors in multiple states, this could be a significant limitation.
Plan benefits, networks, and costs change every year. You need to review your plan annually during the Annual Enrollment Period (October 15 through December 7).

The one-way door

This is one of the most important things to understand before choosing: switching from Medicare Advantage back to Original Medicare may not come with guaranteed access to a Medigap plan.

When you first become eligible for Medicare, you have a one-time Medigap Open Enrollment Period: 6 months, starting when you are both 65 or older and enrolled in Part B. During this window, insurers generally cannot use medical underwriting, and you can buy any Medigap plan sold in your state regardless of health status.

If you choose Medicare Advantage first and later decide to switch to Original Medicare, your Medigap Open Enrollment Period may have already closed. Outside that window, insurers in most states can deny you a Medigap plan or charge significantly more based on your health history. Some states have additional protections: Connecticut and New York offer guaranteed-issue Medigap year-round, Massachusetts and Maine have annual enrollment windows, and some states (including California and Oregon) have birthday rules that only let people who already have Medigap switch plans. Most states offer none of these.

There is a limited Medicare Advantage trial right: if you joined a Medicare Advantage plan when you were first eligible for Medicare, you generally have 12 months to switch back to Original Medicare and buy a Medigap plan with guaranteed issue. After that window closes, you may not get another chance to buy Medigap without underwriting.

The practical implication: Choosing Medicare Advantage is effectively a one-way door for many consumers. If there's a reasonable chance you'll want the freedom to see any Medicare-accepting provider without network restrictions in the future, weigh that possibility now.

What determines which path is better for you:

If provider choice and geographic flexibility matter most (you travel, see specialists in different states, or don't want to deal with referrals and prior authorization): the Original Medicare + Medigap path may be the better fit.
If keeping monthly costs low matters most and you're comfortable using in-network providers in your area: Medicare Advantage may save you money, especially if your plan includes drug, dental, vision, and hearing coverage.
If you take expensive medications: Compare Part D standalone plans (on the Original Medicare path) with the drug coverage built into Medicare Advantage plans. The formulary and cost-sharing on your specific drugs may favor one path over the other.
If you have a chronic condition or expect significant healthcare use: Run the numbers both ways. The Medigap path has higher premiums but more predictable total costs. The Advantage path has lower premiums but potentially higher costs when you use care, up to the plan's out-of-pocket maximum.

Go deeper: Original Medicare vs. Medicare Advantage · Advantage vs. Original Medicare + Medigap · What is Medigap? · What is Medicare Advantage?

5. If Original Medicare: which Medigap plan and which Part D plan?

What you're deciding: Which specific supplemental plans to add to Original Medicare.

Eligibility check: To buy a Medigap plan, you must be enrolled in Medicare Part A and Part B. Medigap plans supplement Original Medicare only. You cannot use a Medigap plan with Medicare Advantage. To enroll in a standalone Part D plan, you must be enrolled in Part A and/or Part B and not be getting drug coverage through a Medicare Advantage plan.

Choosing a Medigap plan

In most states, Medicare Supplement plans are standardized by letter (A, B, C, D, F, G, K, L, M, N); Massachusetts, Minnesota, and Wisconsin standardize their plans differently. Benefits within each letter are the same regardless of which insurance company sells the plan, but premiums vary by company. The differences between carriers are price, customer service, and company stability.

Plans F and C are not available to people who became newly eligible for Medicare on or after January 1, 2020. If you're turning 65 now, these are not options for you.

For most new enrollees, the decision comes down to two plans:

Plan G covers most of the cost-sharing Original Medicare leaves behind, except the annual Part B deductible ($283 in 2026; CMS sets it each year). It does not cover services Medicare itself doesn't cover, such as dental, vision, hearing aids, or long-term care. After you pay that deductible, Plan G generally leaves you with $0 out-of-pocket costs for Medicare-covered services. Plan G is the most widely held Medigap plan, covering about 46% of all Medigap policyholders (KFF, 2025 data).
Plan N covers most of the same gaps as Plan G but with two differences: you may pay a copay of up to $20 for some office visits and up to $50 for emergency room visits that don't result in an admission. In exchange, Plan N premiums are typically lower than Plan G. Plan N holds roughly 10% of Medigap enrollment.

The math question: Compare the annual premium difference between Plan G and Plan N in your area. If the savings on Plan N premiums are greater than what you'd expect to pay in copays over the year, Plan N may cost less overall. If you see doctors frequently or want the simplest cost structure, Plan G eliminates almost all out-of-pocket uncertainty.

Across all plans, about 13 million Americans carry Medigap coverage, just under half of the people in Original Medicare (KFF, 2024-2025 data).

What to watch out for: Medigap premiums vary significantly by carrier, even for the same plan letter in the same ZIP code. Medigap plans are priced using one of three methods: community-rated (same premium regardless of age), issue-age-rated (premium based on your age when you buy), or attained-age-rated (premium increases as you age). Know which method your carrier uses, because it affects what you'll pay over time.

Your Medigap Open Enrollment Period is effectively a one-time window. The 6 months starting when you are both 65 or older and enrolled in Part B is generally the only time you are guaranteed the right to buy any Medigap plan in your state without medical underwriting. After this window closes, insurers in most states can deny coverage, charge higher premiums, or impose waiting periods based on your health. Limited exceptions exist: the 12-month Medicare Advantage trial right, certain guaranteed-issue situations (for example, if your plan leaves your area or shuts down), and extra rights in some states. Do not let this window pass without making a deliberate decision.

Choosing a Part D plan

Original Medicare does not cover most prescription drugs. If you don't enroll in a Part D plan (or have other creditable drug coverage) when you're first eligible, you may face a permanent late enrollment penalty. See Decision 9.

How to choose:

Start with your medication list. The right Part D plan depends entirely on which drugs you take, what doses, and which pharmacy you use. A plan with a low premium may cost more overall if your medications are on a higher formulary tier or not covered at all.
Use a plan comparison tool. Medicare.gov's Plan Finder lets you enter your medications and pharmacy to compare estimated annual costs across plans in your area.
Check the formulary. Every Part D plan has its own list of covered drugs organized into cost-sharing tiers. Your specific medications determine which plan offers the best value.
Review your Part D plan every year during the Annual Enrollment Period (October 15 through December 7). Formularies, premiums, and pharmacy networks change annually, and the best plan for you this year may not be the best plan next year.

The annual out-of-pocket cap, introduced in 2025 and indexed annually ($2,100 in 2026, rising to $2,400 in 2027), limits what you pay out of pocket for covered Part D drugs each year. Once you reach that cap, your plan covers the remaining costs for the rest of the year. This is a significant protection, especially for consumers with expensive prescriptions.

Go deeper: What is Part D? · How to choose a Part D plan · What is Medigap? · Plan letter comparison · Medigap enrollment timing

6. If Medicare Advantage: what should I look for in a plan?

What you're deciding: Which Medicare Advantage plan fits your healthcare needs and budget.

Eligibility check: You must be enrolled in Medicare Part A and Part B and live in the plan's service area. Medicare Advantage plans are local (or sometimes regional), so your options depend on where you live. Some areas have dozens of plans to choose from. Others have only a few.

What to evaluate

Network and providers. This is the most important factor for most people. Check whether your current doctors, specialists, hospitals, and preferred facilities are in the plan's network. Medicare Advantage plans generally require you to use in-network providers (except in emergencies), and going out of network may mean paying the full cost yourself. If you're considering an HMO, you'll typically need a referral to see a specialist. PPO plans offer more flexibility but may cost more for out-of-network care.

Drug coverage. Most Medicare Advantage plans include Part D drug coverage (called MA-PD plans). Check the plan's formulary against your medication list, just as you would with a standalone Part D plan. The drug coverage built into a Medicare Advantage plan varies by plan, and a $0-premium plan could cost you more overall if your medications aren't well-covered.

The out-of-pocket maximum. Every Medicare Advantage plan has an annual out-of-pocket maximum for in-network Medicare-covered services. This is a protection Original Medicare does not offer. But the maximum varies by plan and can be several thousand dollars. A lower maximum provides more financial protection; a higher maximum may come with a lower premium or richer benefits in other areas.

Extra benefits. Many plans include dental, vision, hearing, fitness programs (like SilverSneakers), over-the-counter allowances, transportation to medical appointments, and meal delivery after a hospital stay. These benefits can be valuable, but they vary widely in scope. A plan that advertises "dental coverage" may only cover preventive cleanings, not major work. Read the details.

Prior authorization requirements. Medicare Advantage plans may require you to get the plan's approval before certain tests, procedures, surgeries, or medications. This is one of the biggest behavioral differences from Original Medicare, where you and your doctor generally make care decisions without plan approval. (One exception: since January 1, 2026, a CMS pilot program called WISeR adds prior-authorization review for select services under Original Medicare in Arizona, New Jersey, Ohio, Oklahoma, Texas, and Washington. It does not apply to Medicare Advantage.) Ask about prior authorization policies for services you currently use or expect to need.

Plan stability. Medicare Advantage plans can change their benefits, networks, premiums, and cost-sharing every year. A plan that works well this year could look very different next year. You should review your plan annually during the Annual Enrollment Period (October 15 through December 7).

What to watch out for: The $0 premium on many Medicare Advantage plans can be misleading. You still pay the Part B premium. And a $0-premium plan may have higher copays, coinsurance, or a higher out-of-pocket maximum than a plan with a modest monthly premium. Compare total expected costs, not just the premium.

Switching back to Original Medicare. If you enroll in Medicare Advantage and later want to switch to Original Medicare, you can do so during the Medicare Advantage Open Enrollment Period (January 1 through March 31) or during the Annual Enrollment Period. But as described in Decision 4, switching back may not come with the right to buy a Medigap plan without medical underwriting. Understand this before you enroll.

Go deeper: What is Medicare Advantage? · Advantage enrollment periods · Switch from Advantage to Original Medicare

7. What about dental, vision, and hearing?

What you're deciding: How to get dental, vision, and hearing coverage that Medicare largely doesn't provide.

Eligibility check: This applies to everyone on Medicare. Original Medicare covers very limited dental (certain dental procedures that are part of a covered medical treatment), limited vision (medical eye conditions, but not routine exams for glasses or contacts), and limited hearing (diagnostic hearing exams, but generally not hearing aids or routine hearing tests). For practical purposes, assume you need separate coverage for routine dental, vision, and hearing services.

Your options

If you chose Original Medicare + Medigap: Medigap plans do not cover dental, vision, or hearing. You'll need standalone plans for any of these you want covered. Standalone dental and vision plans are generally available year-round with no medical underwriting.

If you chose Medicare Advantage: Many plans include some dental, vision, and hearing benefits. But the scope varies dramatically. Some plans cover only preventive dental (cleanings and exams) while others include comprehensive dental with coverage for crowns, dentures, and implants. Check the specifics of your plan before assuming these benefits meet your needs. If your Medicare Advantage plan's dental or vision benefit is minimal, you can still buy a standalone plan.

Dental on Medicare

Most dental plans cover preventive care at or near 100%, basic services at around 70-80%, and major services at around 50%, with waiting periods of 6-12 months for major work and annual maximums typically between $1,000 and $2,000.

If you need major dental work soon, a dental discount plan (negotiated rates, not insurance) may be more practical because there are no waiting periods. Dental discount plans are not insurance: you pay a membership fee for access to reduced rates from participating dentists.

Vision and hearing

Vision plans typically cover an annual eye exam and an allowance toward glasses or contacts. Hearing benefits, when available through standalone plans or Medicare Advantage, may include hearing exams and discounts or allowances on hearing aids.

Go deeper: Does Medicare cover dental, vision, or hearing? · Dental on Medicare

8. What happens to my current coverage?

What you're deciding: How to transition from your existing health insurance to Medicare without a gap or unnecessary overlap.

Eligibility check: This section covers the most common pre-Medicare coverage situations. Your specific situation determines your transition path:

If you have employer coverage through active employment

If you or your spouse are still actively working and covered by a job-based group plan, you generally can delay Medicare Part B without penalty. If the employer has 20 or more employees, the job plan pays first; if it has fewer than 20, Medicare usually pays first, so the job plan may pay little or nothing unless you also have Part B. Check with the employer's benefits office before delaying. When the employment or the employer coverage ends, whichever comes first, you have an 8-month Special Enrollment Period to sign up for Part B without penalty. Don't wait for COBRA or retiree coverage to run out: they do not extend this window.

Sign up for Part A if it's premium-free. There is generally no reason to delay Part A when it costs nothing, and some employer plans work better as secondary coverage alongside Part A. One important exception: if you contribute to a health savings account (HSA), enrolling in any part of Medicare, even premium-free Part A, ends your ability to contribute. And if you sign up after 65, Part A coverage can be backdated up to 6 months, which can make recent HSA contributions ineligible.

Do not delay Part B if your employer has fewer than 20 employees. In that case, Medicare generally pays first once you're eligible, and the employer plan pays second. The employer plan may not pay for care that Part B would have covered, so delaying Part B in this situation could leave you with significant coverage gaps.

If you have a Marketplace (ACA) plan

You must transition from your Marketplace plan to Medicare. You cannot receive premium tax credits for any month you are eligible for premium-free Part A, even if you haven't enrolled yet. Continuing a Marketplace plan with subsidies after becoming Medicare-eligible could mean owing those credits back at tax time.

What to do: Enroll in Medicare during your Initial Enrollment Period. Once your Medicare coverage starts, cancel your Marketplace plan. Time it so there's no gap: your Medicare effective date should align with or precede the end of your Marketplace coverage.

If you have COBRA

COBRA coverage does not count as coverage from an active employer for Medicare Part B delay purposes. If you're on COBRA when you turn 65, enroll in Medicare during your Initial Enrollment Period. Once you have Medicare, COBRA generally becomes secondary or may end, depending on the plan.

Do not rely on COBRA to avoid enrolling in Medicare. Delaying Part B because you have COBRA will trigger the permanent Part B late enrollment penalty.

If you have Medicaid

If you have both Medicare and Medicaid eligibility (sometimes called "dual eligible"), you may qualify for programs that help pay Medicare premiums, deductibles, and copays. Your state Medicaid office can explain what assistance is available in your situation.

If you have retiree coverage from a former employer

Retiree coverage is not the same as active employer coverage. It generally does not qualify you to delay Part B without penalty. Most retiree plans expect you to enroll in Medicare when eligible and become secondary coverage (paying after Medicare pays). Check with your former employer's benefits office before making assumptions about how retiree coverage coordinates with Medicare.

Go deeper: Marketplace to Medicare transition · Medicare and employer coverage

9. What are the penalties if I get the timing wrong?

What you're deciding: Whether your enrollment timeline puts you at risk for permanent cost increases.

This is the section many people wish they had read first. Medicare's Part B and Part D late enrollment penalties add to your premiums for as long as you have that coverage, so for most people they never go away. (The Part A penalty is different: it lasts only twice the number of years you delayed.) Understanding these penalties is essential to making a safe enrollment decision.

Part B late enrollment penalty

If you don't sign up for Part B when you're first eligible and you don't have qualifying coverage that allows you to delay (coverage through your own or your spouse's current employer), your premium goes up by 10% of the standard premium for each full 12-month period you could have had Part B but didn't, for as long as you have Part B.

Example: If your sign-up window ended 3 months after you turned 65 and you enrolled at 68 without qualifying employer coverage, that's about 33 months, or 2 full 12-month periods. Your Part B premium would be 20% higher than the standard premium, every month, for as long as you have Part B.

This penalty doesn't expire on its own. It's added to whatever the standard Part B premium is each year, for as long as you keep Part B.

What qualifies as a valid reason to delay: Coverage through your own or your spouse's current employer (active employment). Employer size matters for a related question, who pays first: if the employer has fewer than 20 employees, Medicare usually pays first and the job plan may pay little or nothing unless you also have Part B, so check with the benefits office before delaying. COBRA, retiree coverage, Marketplace plans, and VA coverage do not qualify for penalty-free Part B delay. TRICARE points the same direction: retirees generally must have Part B to stay eligible for TRICARE, so don't delay it either.

Part D late enrollment penalty

If you go 63 or more consecutive days without creditable prescription drug coverage after your Initial Enrollment Period ends, you will pay a permanent surcharge calculated as 1% of the national base beneficiary premium for each month you went without creditable coverage.

Example: If you went 24 months without creditable drug coverage, your penalty would be 24% of the national base beneficiary premium, added to your Part D premium every month for as long as you have Medicare drug coverage.

Like the Part B penalty, this lasts for as long as you have Medicare drug coverage. It does not compound: the penalty stays at 1% of the national base beneficiary premium ($38.99 in 2026) for each full month you went without creditable coverage, but the dollar amount can change each year as that base premium changes. "Creditable coverage" means drug coverage that is at least as good as a standard Medicare Part D plan, and the provider of that coverage should notify you annually whether it qualifies.

What to watch out for: Even if you don't take any prescriptions now, enrolling in a Part D plan (or having other creditable drug coverage) when you're first eligible prevents this penalty. Your prescription needs may change as you age, and paying a permanent surcharge because you delayed is a cost that never makes sense in retrospect.

Medigap Open Enrollment Period

The Medigap Open Enrollment Period is not technically a penalty, but the consequences of missing it function like one. This 6-month window, starting when you are both 65 or older and enrolled in Part B, is generally the only time you are guaranteed the right to buy any Medigap plan in your state at the standard rate, regardless of your health. Limited exceptions exist: the 12-month Medicare Advantage trial right, certain guaranteed-issue situations (such as a plan leaving your area or shutting down), and extra rights in some states.

After this window closes, Medigap insurers in most states can use medical underwriting: they can deny your application, charge higher premiums, or impose waiting periods for pre-existing conditions. If your health has changed since you turned 65, you may find Medigap coverage unavailable or unaffordable.

Some states offer additional protections. Connecticut and New York offer guaranteed-issue Medigap year-round. Massachusetts and Maine have annual enrollment windows. Several other states, including California and Oregon, have birthday rules that let people who already have Medigap switch plans without underwriting, but those rules don't help you buy Medigap for the first time. In most states, this window is functionally one-time.

Part A late enrollment penalty

Most people qualify for premium-free Part A and face no penalty issue. But if you don't qualify for premium-free Part A (because you don't have enough work history) and you don't sign up when first eligible, the penalty is a 10% surcharge on the Part A premium for twice the number of years you delayed.

IRMAA surcharges

These are not penalties for late enrollment, but they are additional costs that catch some new enrollees by surprise. If your modified adjusted gross income from your tax return two years prior is above set thresholds ($109,000 for single filers and $218,000 for joint filers in 2026), you pay higher premiums for both Part B and Part D. These Income-Related Monthly Adjustment Amounts (IRMAA) are not permanent. They adjust each year based on your income, and if you've retired or your income has dropped because of a life-changing event, you can ask Social Security for a new determination using Form SSA-44.

Go deeper: Part B late enrollment penalty · Part D late enrollment penalty · Medigap enrollment timing · IRMAA surcharges

Your action plan and timeline

6 months before you turn 65

Check your eligibility. Confirm your work history (or your spouse's) qualifies you for premium-free Part A. You can check your status by creating an account at ssa.gov.
Find out if you'll be automatically enrolled. If you're already receiving Social Security, you generally will be. If not, you need to sign up yourself.
Review your current coverage. Understand how your existing insurance (employer, Marketplace, COBRA, or other) will interact with Medicare. If you have employer coverage and plan to keep working, confirm that it qualifies you for a penalty-free Part B delay.
Start learning the Original Medicare vs. Medicare Advantage decision. You don't need to decide yet, but understanding the tradeoffs takes time.

3 months before you turn 65 (your IEP opens)

Sign up for Part A and Part B if you're not automatically enrolled. Apply through ssa.gov, by phone, or in person at your local Social Security office. Signing up in the first 3 months of your IEP gives you the earliest possible coverage start date.
If you have qualifying employer coverage and plan to delay Part B, confirm in writing with your employer's benefits office that your coverage qualifies. Keep documentation.

During your birthday month (or within the first month of Part B coverage)

Make your coverage path decision: Original Medicare + Medigap + Part D, or Medicare Advantage.
If Original Medicare: Your Medigap Open Enrollment Period begins when Part B starts. You have 6 months. Do not wait until the end of this window. Compare Medigap plans (focus on Plan G vs. Plan N) and Part D plans in your area.
If Medicare Advantage: Compare plans based on network (are your doctors in?), drug formulary (are your medications covered?), out-of-pocket maximum, and extra benefits. Enroll during your Initial Enrollment Period.

Within 6 months of Part B starting

If you chose Original Medicare, enroll in a Medigap plan before your Open Enrollment Period closes. This is your guaranteed-issue window. After it closes, access is not guaranteed.
Enroll in a Part D plan if you haven't already (either standalone on the Original Medicare path or included in your Medicare Advantage plan). Avoiding the permanent Part D penalty requires having creditable drug coverage.

Transition your old coverage

Cancel your Marketplace plan once Medicare coverage starts. Stop premium tax credits to avoid owing money back.
Coordinate with your employer if transitioning from employer coverage. Understand when employer coverage ends and when Medicare begins.
Set up dental, vision, and hearing coverage if your chosen path doesn't include it.

Every year during the Annual Enrollment Period (October 15 through December 7)

Review your Part D plan (or your Medicare Advantage plan). Formularies, premiums, and networks change annually.
Compare your options even if you're satisfied with your current coverage. A plan that was the best value last year may not be this year.

When to get help

Medicare enrollment is manageable for many people, but some situations involve timing rules, coverage transitions, and plan comparisons that benefit from personalized guidance.

Consider getting help if:

You're still working past 65 and unsure whether your employer coverage qualifies you for a penalty-free Part B delay.
You're transitioning from a Marketplace plan and need to time the switch correctly.
You have a chronic condition or expensive medications and need to compare the total cost of Original Medicare + Medigap + Part D versus specific Medicare Advantage plans.
You're unsure whether Original Medicare or Medicare Advantage is the right fit for your healthcare use and budget.
Your income may trigger IRMAA surcharges and you want to understand the cost impact.

For plan comparison and enrollment help: A licensed agent or broker can help you compare Medicare Supplement, Medicare Advantage, and Part D plans at no additional cost to you. Healthcare.com's licensed agents can walk through your options.

For Medicare-specific counseling: Your state's SHIP (State Health Insurance Assistance Program) provides free, unbiased Medicare counseling. SHIP counselors are not selling plans and can help with enrollment decisions, appeals, and billing questions.

For employer coverage coordination: Your employer's HR or benefits office can confirm whether your group plan qualifies for penalty-free Part B delay and how coverage coordinates with Medicare.

This guide provides general educational information, not legal, tax, or financial advice. Plan availability, pricing, eligibility, and benefits depend on individual circumstances, location, and the current plan year, and may change. Consult a licensed agent, tax professional, or benefits counselor for advice specific to your situation.