Turning 65? Your Complete Medicare Enrollment Checklist

Why You Need a Medicare Enrollment Plan

Turning 65 is one of the most important milestones in your healthcare journey. It is the age when most Americans become eligible for Medicare — and the decisions you make during this window will shape your coverage, your costs, and your access to care for years to come.

The problem is that Medicare enrollment is not automatic for everyone, the rules are specific, and missing a deadline can result in permanent penalties. This checklist walks you through every step — from six months before your 65th birthday through the three months after — so you can enroll with confidence and avoid costly mistakes.

Understanding Your Initial Enrollment Period (IEP)

Your Initial Enrollment Period is the 7-month window centered around your 65th birthday. It is the single most important enrollment window you will ever have, because it determines when your coverage starts and whether you face late enrollment penalties.

The IEP consists of three phases:

1. 3 months before your birth month — If you sign up during this phase, coverage typically starts the first day of your birth month.
2. Your birth month — If you sign up during your birth month, coverage starts the first day of the following month.
3. 3 months after your birth month — If you sign up in the month after your birthday, coverage starts two months later. Sign up two or three months after, and coverage is delayed even further.

The takeaway is simple: sign up as early as possible within your IEP. The earlier you enroll, the sooner your coverage begins and the less risk you carry of a gap in protection.

6 Months Before Your 65th Birthday

Six months out is the time to start planning, not enrolling. Use this period to get organized and understand your options.

• Gather your information. Locate your Social Security number, any employer insurance cards, a list of your current medications (with dosages), and the names and addresses of your doctors and specialists.
• Review your current coverage. If you have employer or union health insurance, contact your benefits department and ask whether it counts as "creditable coverage" — this matters for avoiding Part B and Part D late enrollment penalties.
• Learn the four parts of Medicare. Part A covers hospital care, Part B covers outpatient and doctor services, Part C (Medicare Advantage) is the private plan alternative, and Part D covers prescription drugs. Understanding these parts now will make every subsequent decision easier.
• Create a list of your healthcare priorities. Do you want to keep your current doctors? Do you need coverage for specific prescriptions? Do you travel frequently? Would you prefer lower monthly premiums or more predictable out-of-pocket costs? Answering these questions now will guide your plan choice later.
• Check your Social Security status. If you are already receiving Social Security benefits, you will be automatically enrolled in Medicare Parts A and B when you turn 65. If you are not receiving Social Security, you will need to actively sign up.

3 Months Before Your 65th Birthday

This is when your Initial Enrollment Period officially opens. If you are not being automatically enrolled, this is the time to act.

• Sign up for Medicare Part A and Part B. You can enroll online at SSA.gov, by calling Social Security at 1-800-772-1213, or by visiting your local Social Security office. Enrolling in the first month of your IEP ensures coverage starts the first day of your birth month.
• Decide between Original Medicare and Medicare Advantage. This is the fundamental fork in the road. Original Medicare (Parts A and B) lets you see any provider nationwide that accepts Medicare, but has no out-of-pocket maximum and does not cover dental, vision, or hearing. Medicare Advantage bundles everything into one plan with added benefits and an annual spending cap, but limits you to a provider network.
• Research Part D prescription drug plans. If you choose Original Medicare, you will need a standalone Part D plan for drug coverage. Use the Medicare Plan Finder at Medicare.gov to compare plans by entering your zip code and current medications. If you choose Medicare Advantage, most plans include Part D.
• Verify your doctors accept Medicare. If you plan to stick with Original Medicare, confirm that your providers accept Medicare assignment. If you are considering Medicare Advantage, verify your doctors and preferred hospitals are in the plan's network.
• Look into Medigap (Medicare Supplement) policies. If you choose Original Medicare, a Medigap policy can help cover the 20% coinsurance, deductibles, and other out-of-pocket costs. Your Medigap Open Enrollment Period starts when you turn 65 and are enrolled in Part B — and it lasts only 6 months. During this window, insurers cannot deny you or charge more due to pre-existing conditions.

Your Birthday Month

If you enrolled during the first three months of your IEP, your Medicare coverage should now be active. If you have not yet enrolled, do it now — every month of delay pushes your coverage start date further out.

• Confirm your Medicare card has arrived. Your red, white, and blue Medicare card should arrive in the mail about a month before your coverage begins. It shows your Medicare number and the effective dates for Part A and Part B.
• Set up your MyMedicare.gov account. This online portal lets you view your coverage details, track claims, compare plans, and manage your benefits.
• Coordinate with employer coverage if applicable. If you are continuing to work and keeping employer insurance, confirm with your HR department how your employer plan coordinates with Medicare. In most cases, if your employer has 20 or more employees, employer coverage remains primary and Medicare is secondary.
• Finalize your Medigap enrollment. If you selected Original Medicare and want a Medigap policy, apply during your 6-month Medigap Open Enrollment Period. This is your best — and in many states your only — guaranteed-issue opportunity.

3 Months After Your 65th Birthday

Your IEP closes at the end of the third month following your birth month. If you have not yet enrolled in Part A or Part B, this is your final chance before facing potential penalties and waiting for the General Enrollment Period.

• Complete any remaining enrollment steps. If you still need to enroll in Part A, Part B, Part D, or a Medicare Advantage plan, do so immediately. Waiting until the last month means your coverage will not start for another two to three months.
• Drop any coverage you no longer need. If you were on a Marketplace (ACA) plan, cancel it once your Medicare coverage is active to avoid paying for overlapping policies. Note that Marketplace premium subsidies are not available to people who are eligible for Medicare.
• Schedule your "Welcome to Medicare" preventive visit. Part B covers a one-time preventive exam within the first 12 months of your Part B coverage. This visit is free and establishes a baseline for your health going forward.
• Review your plan documents carefully. Whether you chose Original Medicare, Medicare Advantage, or a standalone Part D plan, read the plan materials so you understand your deductibles, copays, formulary, network, and how to file claims or appeals.

Automatic Enrollment vs. Manual Enrollment

Not everyone has to actively sign up for Medicare. Whether you are automatically enrolled or need to take action depends on your Social Security status.

You are automatically enrolled if:

• You are already receiving Social Security retirement benefits before you turn 65.
• You are receiving Railroad Retirement Board benefits.
• You have been receiving Social Security Disability Insurance (SSDI) for 24 months.

If you fall into one of these categories, you will receive your Medicare card in the mail about three months before your 65th birthday. You will be enrolled in both Part A and Part B automatically.

You must manually enroll if:

• You have not yet filed for Social Security benefits (for example, you plan to delay benefits until age 66, 67, or 70).
• You are still working and covered by an employer plan and want to delay Part B.

Important: Even if you are automatically enrolled, you still need to separately enroll in a Part D drug plan, a Medicare Advantage plan, or a Medigap policy. Automatic enrollment only covers Parts A and B.

What to Do If You Are Still Working with Employer Coverage

Many people turning 65 are still employed and covered by a group health plan through their employer or their spouse's employer. If that is your situation, the rules for Medicare enrollment are different — and the size of the employer matters.

Employer with 20 or more employees:

• Your employer plan is the primary payer and Medicare is secondary.
• You can delay enrolling in Part B without penalty, as long as you or your spouse are still actively working and you are covered by the employer plan.
• Most people in this situation sign up for premium-free Part A at 65 (there is no reason not to) and delay Part B until they retire or lose employer coverage.
• When you do leave employer coverage, you qualify for a Special Enrollment Period — an 8-month window to sign up for Part B without a late penalty.

Employer with fewer than 20 employees:

• Medicare is the primary payer and your employer plan is secondary.
• You should sign up for both Part A and Part B during your IEP to avoid penalties and coverage gaps.
• If you do not enroll in Part B and your employer plan is secondary, your medical claims may go largely unpaid.

Critical warning: COBRA and retiree health plans do not count as employer "group" coverage for the purpose of delaying Part B enrollment. If you are on COBRA when you turn 65, you must sign up for Medicare during your IEP or risk permanent penalties.

Choosing Between Original Medicare and Medicare Advantage

This is the biggest decision you will make during your enrollment process. Neither option is universally better — the right choice depends entirely on your personal situation.

Choose Original Medicare if:

• You want the freedom to see any doctor or specialist in the country who accepts Medicare — no referrals needed.
• You travel frequently, split time between states, or live in a rural area with limited plan networks.
• You have complex or ongoing health needs and want guaranteed access to top specialists without prior authorization.
• You are willing to pair it with a Medigap policy and a standalone Part D plan for comprehensive protection.

Choose Medicare Advantage if:

• You want one plan that bundles hospital, medical, drug, and often dental, vision, and hearing coverage.
• You prefer lower premiums and are comfortable using an HMO or PPO network of providers.
• You want an annual out-of-pocket maximum — something Original Medicare does not offer.
• You value extra benefits like fitness programs, transportation to appointments, and over-the-counter allowances.

Keep in mind: You cannot have a Medigap policy and a Medicare Advantage plan at the same time. If you choose Medicare Advantage, Medigap is off the table. And if you later decide to switch back to Original Medicare and want a Medigap policy, you may face medical underwriting — meaning you could be denied coverage or charged higher premiums based on your health history.

Enrolling in Part D Prescription Drug Coverage

Prescription drug coverage is not included in Original Medicare (Parts A and B). If you go the Original Medicare route, you must enroll in a standalone Part D plan separately. If you choose Medicare Advantage, most MA plans include Part D drug coverage.

When comparing Part D plans, focus on:

• Formulary: Make sure all of your current prescriptions are on the plan's list of covered drugs.
• Tier placement: Lower tiers mean lower copays. A plan might cover your drug but place it on a high-cost specialty tier.
• Pharmacy network: Verify that your preferred pharmacy — including mail-order options — is in the plan's network.
• Total annual cost: Do not just look at the monthly premium. The Medicare Plan Finder estimates your total yearly cost including premiums, deductibles, and copays for your specific medications.

Part D late enrollment penalty: If you go 63 or more consecutive days without creditable drug coverage after your Initial Enrollment Period, you will pay a permanent penalty added to your Part D premium. The penalty is calculated as 1% of the national base beneficiary premium multiplied by the number of months you went without coverage — and it never goes away.

Your Medigap Open Enrollment Period

If you choose Original Medicare, a Medigap (Medicare Supplement) policy is one of the most important additions you can make. These standardized policies — labeled Plan A through Plan N — help cover the gaps in Original Medicare, including the Part B coinsurance, hospital deductibles, and in some cases excess charges.

Your Medigap Open Enrollment Period is the 6-month window that begins the month you are both age 65 or older and enrolled in Medicare Part B. This is the only time federal law guarantees your right to buy any Medigap policy sold in your state, regardless of your health status.

During this window:

• Insurance companies cannot deny your application due to pre-existing conditions.
• They cannot charge you more because of past or current health problems.
• They cannot impose a waiting period for coverage of pre-existing conditions (with limited exceptions for conditions treated within six months before the policy effective date).

After this 6-month window closes, there is no federal guarantee. In most states, insurers can use medical underwriting to decide whether to sell you a policy and how much to charge. This means if you develop a health condition, you may not be able to get a Medigap policy later — or it could cost significantly more.

Common Mistakes to Avoid

Every year, thousands of new Medicare beneficiaries make preventable errors that cost them money or leave them without coverage. Here are the most common mistakes — and how to avoid them.

1. Missing the Initial Enrollment Period entirely. If you miss your IEP and do not have qualifying employer coverage, you will have to wait until the General Enrollment Period (January 1 through March 31) to enroll. Coverage will not start until July 1, and you may face a permanent Part B late penalty of 10% for each full 12-month period you were eligible but not enrolled.
2. Assuming COBRA counts as employer coverage. COBRA is continuation coverage, not active employer group coverage. It does not protect you from Medicare late enrollment penalties. If you are on COBRA when you turn 65, enroll in Medicare immediately.
3. Skipping Part D because you do not take medications. Even if you are healthy and take no prescriptions today, skipping Part D can be expensive down the road. The late enrollment penalty accrues for every month you go without creditable drug coverage — and it is added to your premium permanently once you do enroll.
4. Missing the Medigap Open Enrollment window. Your 6-month guaranteed-issue period for Medigap starts automatically, and once it closes, most states do not require insurers to accept you. Waiting to buy Medigap after this window can mean medical underwriting, higher premiums, or outright denial.
5. Not verifying that your doctors accept your plan. Whether you choose Original Medicare or Medicare Advantage, always confirm that your current doctors, specialists, and preferred hospitals participate before you finalize your enrollment. Switching plans later to get your providers back in-network is not always possible outside of specific enrollment windows.
6. Confusing Medicare enrollment with Social Security. You can enroll in Medicare at 65 without filing for Social Security retirement benefits. Many people delay Social Security to maximize their monthly benefit but still need to sign up for Medicare on time.
7. Enrolling in a Marketplace plan after becoming Medicare-eligible. Once you are eligible for Medicare, you lose access to Marketplace (ACA) premium subsidies. Keeping a Marketplace plan alongside Medicare is allowed but rarely makes financial sense.

Step-by-Step Action Items

Here is a concise action list you can follow in order as you approach and pass your 65th birthday.

1. 6 months out: Gather documents — Social Security number, insurance cards, medication list, doctor names.
2. 6 months out: Confirm whether your employer plan qualifies as creditable coverage.
3. 5 months out: Research the four parts of Medicare and decide whether Original Medicare or Medicare Advantage best fits your needs.
4. 4 months out: Use the Medicare Plan Finder to compare Part D and Medicare Advantage plans in your area.
5. 3 months before birthday: Enroll in Medicare Part A and Part B through SSA.gov, by phone, or in person.
6. 3 months before birthday: Enroll in a Part D plan or Medicare Advantage plan.
7. Birthday month: Confirm your Medicare card has arrived. Set up your MyMedicare.gov account.
8. Birthday month: Apply for a Medigap policy if you chose Original Medicare (your 6-month Medigap OEP begins).
9. Within 3 months after birthday: Cancel any overlapping Marketplace coverage.
10. Within 3 months after birthday: Schedule your free "Welcome to Medicare" preventive visit.
11. Within 3 months after birthday: Review all plan documents and keep your Medicare card in a safe place.

Frequently Asked Questions

What happens if I miss my Initial Enrollment Period? If you miss your IEP and do not have qualifying employer coverage, you will need to wait for the General Enrollment Period (January 1 through March 31). Your Part B coverage will not start until July 1 of that year, leaving you without medical coverage for months. You will also face a permanent Part B late enrollment penalty of 10% for each 12-month period you were eligible but did not enroll.

Can I delay Medicare if I am still working and have employer insurance? Yes, but only under specific conditions. If you or your spouse are actively working and covered by a group health plan from an employer with 20 or more employees, you can delay Part B without penalty. When you leave that employer coverage, you will have an 8-month Special Enrollment Period to sign up. COBRA and retiree plans do not qualify — you must enroll during your IEP if those are your only coverage.

Do I need Part D if I do not take any prescription medications? It is strongly recommended. Even if you are healthy and take no medications today, going without creditable drug coverage triggers a permanent late enrollment penalty. The penalty grows every month you are uncovered and is added to your Part D premium for life once you do enroll. A low-cost Part D plan now can save you significantly over the long term.

Can I switch from Medicare Advantage back to Original Medicare later? Yes, you can switch during the Annual Enrollment Period (October 15 through December 7) or the Medicare Advantage Open Enrollment Period (January 1 through March 31). However, the challenge is getting a Medigap policy afterward. Outside your initial 6-month Medigap Open Enrollment Period, most states allow insurers to use medical underwriting, which means you could be denied or charged significantly more based on your health conditions.

Is there a penalty for not signing up for Part A? For most people, Part A is premium-free because they or their spouse paid Medicare taxes for at least 10 years (40 quarters). In that case, there is no penalty for late enrollment, but there is also no reason to delay — it costs nothing. If you must pay a Part A premium (because you have fewer than 40 quarters of work history), there is a late enrollment penalty: your premium increases by 10% and you must pay the higher amount for twice the number of years you delayed.

How do I sign up for Medicare? You can enroll online at SSA.gov, by calling Social Security at 1-800-772-1213 (TTY: 1-800-325-0778), or by visiting your local Social Security office in person. If you are already receiving Social Security benefits, you will be enrolled automatically and do not need to take action for Parts A and B.

The Bottom Line

Turning 65 and enrolling in Medicare does not have to be overwhelming — but it does require attention to deadlines. The decisions you make during your Initial Enrollment Period will affect your coverage, your costs, and your options for years to come.

Start early. Know your IEP dates. Understand whether you should choose Original Medicare or Medicare Advantage. Do not skip Part D even if you feel healthy. And above all, do not miss your Medigap Open Enrollment window if you go the Original Medicare route — it is the one guaranteed-issue opportunity that you cannot get back.

Use this checklist as your guide, mark the key dates on your calendar, and take it one step at a time. The right Medicare coverage is out there — you just need to enroll on time to get it.