Medicare Enrollment Complete Guide 2026

Most Medicare guides are written by people who've never sat across a table from a 64-year-old in a panic because they just realized they missed a deadline three years ago.

This one isn't.

Medicare enrollment is genuinely confusing — not because the rules are that complicated, but because there are about fourteen different enrollment windows, each with its own logic, and missing the wrong one can cost you hundreds of dollars a month for the rest of your life. That's not hyperbole. The penalties are permanent.

So we're going to go through every enrollment period, every penalty, every exception, and every scenario that trips people up. Real dollar figures. Real timelines. And when something matters a lot, I'm going to say so directly instead of burying it in qualifying language.

If you're turning 65 this year, or you have a parent who is, or you're on disability and don't know when your Medicare kicks in — this is the guide. Read the whole thing or use the sections. Either works.

There are four doors into Medicare, and most people only know about the first one.

**Door 1: Age 65** This is the one everyone knows. You turn 65, you're eligible for Medicare. Specifically, you need to be a U.S. citizen or permanent legal resident who has lived in the U.S. for at least five continuous years. And for premium-free Part A, you or your spouse need at least 40 quarters of Medicare-covered work — roughly 10 years of employment. If you don't hit 40 quarters, you can still buy in. More on that below.

**Door 2: Social Security Disability (SSDI) — 24-Month Waiting Period** If you're under 65 and receiving SSDI benefits, Medicare kicks in automatically after your 24th month of disability benefit payments. Not 24 months after you apply. Not 24 months after your disability started. Twenty-four months after you started collecting SSDI checks.

This waiting period exists because Congress designed it that way in 1972 and has declined to change it ever since, which is cold comfort if you're sick and waiting. But that's the rule. Month 25 is when your Medicare card arrives.

**Door 3: ALS (Lou Gehrig's Disease)** ALS is the only disability where the 24-month waiting period doesn't apply. If you're diagnosed with ALS and approved for SSDI, Medicare begins the same month your SSDI benefits start. No waiting. The logic is that ALS progresses fast enough that making someone wait two years is unconscionable. It's one of the more humane rules in an otherwise bureaucratic system.

**Door 4: End-Stage Renal Disease (ESRD)** ESRD — kidney failure — triggers Medicare eligibility regardless of age, but the timing depends on your treatment. If you start regular dialysis, Medicare coverage begins three months after the month dialysis starts. If you get a kidney transplant, Medicare begins the month you're admitted to a hospital for the transplant. And here's the part people miss: if you participate in a self-dialysis training program, coverage can start the month dialysis begins. The difference between those three scenarios can mean two months of uncovered bills if you don't know which one applies to you.

**Part A Premium — What You'll Actually Pay** If you or your spouse worked at least 40 quarters (10 years) in Medicare-covered employment, Part A is free. Zero dollars a month.

If you have 30 to 39 quarters: $311/month in 2026. Fewer than 30 quarters: $565/month in 2026.

For most people this is a non-issue — roughly 99% of Medicare beneficiaries get premium-free Part A. But if you're a recent immigrant, came to the U.S. later in life, or spent years working abroad, this matters.

**Part B Premium in 2026** The standard Part B monthly premium is $202.90 in 2026. That's up $17.90 from $185.00 in 2025. Higher-income beneficiaries pay more through IRMAA (Income-Related Monthly Adjustment Amount) — we cover that separately, but heads up that the 2026 IRMAA brackets use your 2024 tax return.

Part A inpatient deductible: $1,736 per benefit period in 2026.

Your Initial Enrollment Period — IEP — is a seven-month window. It's built around your 65th birthday month like this:

— 3 months before your birthday month — Your birthday month itself — 3 months after your birthday month

So if you turn 65 on September 14, 2026, your IEP runs June 1 through December 31, 2026. You have all seven of those months to enroll.

But here's where the timing gets important — and where people get burned.

If you enroll in the first three months of your IEP (before your birthday month), coverage starts the first day of your birthday month. Clean.

If you enroll during your birthday month, coverage starts the first day of the following month. One-month delay.

If you enroll in months 5, 6, or 7 of your IEP — the three months after your birthday month — coverage is delayed even further. Under old rules it was a two- or three-month delay. CMS updated this: as of 2023 and continuing into 2026, if you enroll in months 5, 6, or 7 of your IEP, coverage starts the first day of the following month regardless. They actually fixed this one.

The practical advice: enroll three months before your 65th birthday. Don't wait. There's no benefit to waiting, only delays and the risk that you forget.

**What you're enrolling in during IEP** During your IEP, you're enrolling in Original Medicare — Part A and Part B. Once you have those, you can also sign up for a Part D prescription drug plan and/or a Medicare Advantage plan (Part C) to replace Original Medicare.

You do NOT enroll in all of these at the same time through the same place. Part A and B go through Social Security (SSA.gov, 1-800-772-1213, or your local SSA office). Part D and Medicare Advantage plans are separate — you choose a plan through Medicare.gov or directly with an insurer.

**If you're already on Social Security** If you're already receiving Social Security benefits (or Railroad Retirement Board benefits) at least four months before you turn 65, you get automatically enrolled in both Part A and Part B. You don't need to do anything. Your red-white-and-blue Medicare card shows up in the mail three months before your 65th birthday.

But — and this matters — you might not want Part B if you have other coverage. If you're still working and have employer insurance, you may want to delay Part B to avoid paying that $202.90/month premium. If you're auto-enrolled and don't want Part B, you have to actively decline it. There's a form. Don't just not pay the premium and assume it gets dropped — that's not how it works and you'll end up with a penalty situation later.

Three months before your 65th birthday, do these things. In roughly this order.

**Step 1: Check your work history** Go to SSA.gov and look at your Social Security earnings record. Make sure you have at least 40 quarters. If you're close to the line, look at your spouse's record too — spousal work history can qualify you for premium-free Part A. If there are errors in your earnings record, you want to find out now, not when you're already past your IEP.

**Step 2: Decide whether you're enrolling now or delaying** This decision depends entirely on whether you have employer coverage that qualifies as primary insurance. See the 'Medicare and Still Working' section below for the full breakdown. If you're not working or your employer coverage is secondary, you're enrolling now. If you have qualifying employer coverage, you may have the option to delay.

Don't guess here. Call your HR department. Ask specifically: 'Does my employer coverage remain primary to Medicare for someone my age?' Get it in writing if you can.

**Step 3: Enroll in Part A and Part B** Go to SSA.gov/benefits/medicare. You can apply online in about 10-15 minutes. Or call 1-800-772-1213 Monday-Friday 8am-7pm local time. Or go in person to your local Social Security office — but make an appointment, walk-in wait times can be brutal.

For Railroad Retirement recipients, contact the Railroad Retirement Board at 1-877-772-5772 instead of SSA.

**Step 4: Compare Part D plans** Go to Medicare.gov/plan-compare. Enter your zip code and the drugs you take. The site will show you every Part D plan available in your area with their premiums, deductibles, and estimated drug costs based on your specific medications. This tool is genuinely good — use it.

Do not just pick the plan with the lowest monthly premium. The deductible and copays for your specific drugs often matter more.

**Step 5: Decide: Original Medicare + Medigap + Part D, or Medicare Advantage?** This is the big fork in the road and it deserves more than a checklist item — but here's the short version:

*Original Medicare + Medigap (Supplement)* gives you the most flexibility. You can see any doctor in the country who accepts Medicare. Your Medigap plan pays most of what Original Medicare doesn't. You add a separate Part D plan for drugs. More predictable costs, usually higher monthly premiums.

*Medicare Advantage (Part C)* is a private plan that replaces Original Medicare. Usually lower monthly premiums (sometimes $0 above your Part B premium), but you're in a network. Prior authorizations are common. Out-of-pocket maximums are capped (Original Medicare has none). Can be great or terrible depending on your local market and how much healthcare you actually use.

If you're healthy, use few specialists, and want low monthly costs, Advantage might suit you. If you have chronic conditions, see multiple specialists, or travel frequently, Original Medicare plus a Medigap plan is usually the safer choice.

**Step 6: Enroll in your chosen plan** Part D or Medicare Advantage enrollment happens at Medicare.gov or directly with the insurer. Your coverage starts January 1 of the year you turn 65 (if you enrolled in the fall before) or the month after enrollment during your IEP.

**Step 7: Set up premium payment** If you're receiving Social Security, your Part B premium gets deducted automatically. If you're not yet on Social Security, you'll get a bill quarterly from CMS. You can set up automatic bank draft to avoid missing a payment — missed Part B payments can trigger disenrollment, which is a mess.

The Annual Enrollment Period — AEP — runs every year from October 15 through December 7. Changes made during AEP take effect January 1 of the following year.

This is NOT when you first sign up for Medicare. That's what the IEP is for. AEP is for people who already have Medicare and want to change something.

During AEP you can: — Switch from Original Medicare to Medicare Advantage — Switch from Medicare Advantage to Original Medicare — Switch from one Medicare Advantage plan to a different one — Switch from one Part D drug plan to a different one — Drop a Part D plan entirely (risky — see penalty section) — Add a Part D plan if you had Original Medicare without drug coverage

You do NOT need to do anything during AEP if you're happy with your current coverage. Your plan rolls over automatically. But you should at least look, because:

Plans change their formularies every year. A drug that was covered at tier 2 this year might be tier 4 or dropped entirely next year. Premiums change. Networks change. The plan you picked two years ago might not be the best choice anymore.

Medicare.gov sends every beneficiary an Annual Notice of Change (ANOC) from their plan in late September. Read it. Specifically look at: your premium, your drug formulary for any prescriptions you take, and whether your doctors are still in-network if you're on Advantage.

The October 15 through December 7 window is fixed. There are no extensions. If you miss it, you wait until next year unless a qualifying event triggers a Special Enrollment Period.

The Medicare Advantage Open Enrollment Period — MA OEP — runs every year from January 1 through March 31. Changes take effect the first of the month after you enroll.

This period is specifically for people who are already enrolled in a Medicare Advantage plan. It lets you make one change: — Switch to a different Medicare Advantage plan — Switch back to Original Medicare (with or without a Part D plan)

You can only make one change during MA OEP. That's it. If you switch to a new MA plan in February, you can't then switch again in March.

If you switch back to Original Medicare during MA OEP, you should also look at adding a Part D plan at the same time — otherwise you're leaving yourself without drug coverage, which ticks the penalty clock.

Critical point about Medigap during MA OEP: When you switch back to Original Medicare, you'll probably want a Medigap (supplemental) policy to help cover cost-sharing. But here's the catch — outside of certain protected windows, Medigap insurers in most states can reject you or charge higher premiums based on your health history. You get 63 days of guaranteed-issue rights when you leave an MA plan and return to Original Medicare. Miss that window and you're at the mercy of medical underwriting.

The one big exception: if you're within your first 12 months of being on Medicare Advantage (a 'trial period' of sorts), and you switch back to Original Medicare, you have guaranteed-issue rights to buy any Medigap plan in your state. This is federal law. Use it if you're in that situation.

MA OEP is NOT available to people who are on Original Medicare and want to join a Medicare Advantage plan for the first time. That happens during AEP (October 15 - December 7) or during your IEP.

The General Enrollment Period — GEP — also runs January 1 through March 31 every year, but don't confuse it with the MA OEP. They're concurrent but completely different.

The GEP is for people who missed their Initial Enrollment Period and don't qualify for a Special Enrollment Period. It's basically the 'I screwed up' window for Part A and/or Part B enrollment.

If you enroll during GEP, your coverage starts July 1 of that year. Not January 1. July 1. That's a potential six-month gap between when you enroll and when coverage starts, which is worth knowing if you're weighing your options.

GEP enrollment also typically means late enrollment penalties apply. If you should have enrolled at 65 and didn't, enrolling through GEP doesn't erase those penalties — it just gets you enrolled.

Who actually uses GEP? People who were uninsured, didn't realize they needed to sign up, or made assumptions about being automatically enrolled when they weren't. It happens more often than you'd think.

Special Enrollment Periods — SEPs — are the escape hatches. They let you enroll in or change Medicare coverage outside the standard windows when something significant happens in your life. SEPs are specific and rule-bound — not everything qualifies, and timing matters.

**SEP: Losing Employer or Union Coverage** This is the most important SEP. When you or your covered spouse loses employer or union health coverage, you get an 8-month window to enroll in Medicare Part B. Eight months from the day the coverage ends.

This SEP is triggered whether you leave the job voluntarily, get laid off, your employer drops coverage, or the employer goes out of business. The 8-month clock starts the same day your coverage ends.

Note: COBRA does NOT count as qualifying coverage for delaying Part B. If your employer coverage ends and you elect COBRA instead of enrolling in Part B, the 8-month SEP clock starts from when the employer coverage ended — not from when COBRA ends. People lose track of this constantly.

Enroll in Part B during this 8-month window. Don't wait for COBRA to run out.

**SEP: Still Working (Employer Coverage SEP)** If you have coverage from an active employer or union (either your own job or your spouse's), and that employer has 20 or more employees, your employer plan is primary and Medicare is secondary. In this situation, you can delay Part B without penalty for as long as the employment and coverage continue. When that coverage ends, you get the 8-month SEP above.

**SEP: Moving** If you move out of your Medicare Advantage plan's service area, you get a 2-month SEP to switch plans. The SEP starts the month before your move (if you notify the plan in advance) or two months after the move.

For Part D, if you move to a new area and your plan is no longer available, you get a similar SEP to switch plans.

**SEP: Losing Medicaid or Extra Help** If you lose Medicaid eligibility or lose your Low Income Subsidy (Extra Help) for Part D, you get a 3-month SEP to enroll in a new Part D plan.

**SEP: Gaining Medicaid** If you gain Medicaid eligibility, you can enroll in or switch Medicare plans once per quarter during the first three quarters of the year.

**SEP: Moving into or out of a Long-Term Care Facility** Moving into or out of a skilled nursing facility, nursing home, or similar institution is a qualifying event. You get a 2-month SEP.

**SEP: Plan Leaves Your Area** If your Medicare Advantage or Part D plan is discontinued, leaves your service area, or loses its contract with CMS, you get a 2-month SEP to choose a new plan.

**SEP: Five-Star Plan** This is a lesser-known one. If there's a Medicare Advantage or Part D plan in your area with a 5-star CMS quality rating, you can switch to it one time between December 8 and November 30 of the following year — essentially a rolling SEP. Not many plans hit 5 stars, but it's worth checking.

**SEP: Leaving Incarceration** People leaving prison or jail who qualify for Medicare can enroll during the first month before or the month of release, and for two months after.

**SEP: Exceptional Circumstances** CMS can grant SEPs for disasters, system errors, misinformation from a plan or government agency, and other circumstances outside your control. These are case-by-case and require documentation. If a Medicare representative gave you bad information that caused you to miss an enrollment window, document everything and request a Special Enrollment Period — these are granted more often than people realize.

**Timing Rule for Most SEPs** Most SEPs for Medicare Advantage and Part D plans are 2 months from the qualifying event. The Part B SEP for losing employer coverage is 8 months. Know which clock you're on.

This section causes more confusion than almost anything else in Medicare. Let me be direct about how it works.

The rule turns on one number: 20 employees.

**Employer with 20 or more employees** If you're 65 or older, still working, and covered by an employer group health plan from a company with at least 20 employees (or a spouse's employer with 20+), you can delay Medicare Part B without penalty. Your employer plan is primary — it pays first — and Medicare would be secondary if you have it. Since you're paying a Part B premium and Medicare would be secondary anyway, most people in this situation delay Part B and just take Part A (which is free if you have 40+ quarters).

When you eventually retire or lose that coverage, you have an 8-month Special Enrollment Period to sign up for Part B with no penalty.

This is legal and it's exactly what the rules intend.

**Employer with fewer than 20 employees** If your employer has fewer than 20 employees, the math flips. Medicare becomes primary, and your employer plan pays second. In this case, you need to enroll in Medicare at 65 — even if you're still working. If you don't, Medicare won't pay first, your employer plan won't pay first, and you could end up with large unpaid bills because neither payer is covering what they should be.

This one bites people. Small business owners especially. Check your employer's size before assuming you can delay.

**Self-Employed** If you're self-employed and buying your own health insurance, that coverage is not employer coverage for Medicare purposes. You generally need to enroll in Medicare at 65.

**Working Part-Time** Part-time employment can still qualify for the employer coverage delay — as long as you're covered under the employer's group health plan and the employer has 20+ employees. The key is whether you have active employer coverage, not whether you're full-time.

**Union Coverage** Union-sponsored coverage while you're actively working (not retirement union coverage) counts the same as employer coverage. Retiree union coverage is a different situation — it typically doesn't qualify you to delay Part B.

**Spouse's Employer** If you're covered through your still-working spouse's employer plan, and that employer has 20+ employees, you can delay your own Medicare the same way. When your spouse retires or loses coverage, the 8-month SEP applies to you too.

**What to Actually Ask HR** Don't ask HR 'can I delay Medicare?' They might not know. Ask specifically: 1. How many employees does this company have? (For Medicare purposes, count all employees, not just full-time.) 2. Is the company's group health plan primary to Medicare for employees over 65? 3. Will the plan coordinate benefits with Medicare as secondary?

Get the answers in writing. If your plan coordinator tells you Medicare is secondary but you can delay, and they're wrong, that mistake can create years of claim denials and retroactive penalties. Document it.

COBRA and Medicare do not mix well, and the order in which you do things matters enormously.

Here's the scenario that creates problems: You're 65, you retire, you elect COBRA to keep your employer coverage, and you figure you'll sign up for Medicare when COBRA runs out. Eighteen months later, COBRA ends and you go to enroll in Part B. CMS says you owe a late enrollment penalty — for all the months since you turned 65 and stopped having active employer coverage.

Wait, you say. I had COBRA. I had coverage.

Doesn't matter. COBRA is NOT considered active employment or employer coverage for purposes of the Medicare Part B late enrollment penalty. The 8-month Special Enrollment Period clock starts when your active employment coverage ends. COBRA doesn't reset that clock. It doesn't pause it. The clock is running while you're on COBRA.

So if you retire at 65 and elect 18 months of COBRA, by the time COBRA ends you're 6½ months past your 8-month SEP window. You're now in penalty territory.

**The right way to handle this:** When you retire and lose active employer coverage, enroll in Medicare Part A and Part B immediately — within the 8-month SEP window. You can still elect COBRA for supplemental coverage while you figure out your Part D and Medigap options, but get Part A and B locked in first.

Or better: don't use COBRA at all once you have Medicare. COBRA plus Medicare is usually redundant and expensive. Enroll in Medicare, pick a Medigap plan, pick a Part D plan, and skip COBRA entirely. You'll almost certainly pay less out of pocket.

**The exception:** If you're not yet 65 and lose your job, COBRA makes sense as a bridge. But once you hit 65 while on COBRA, enroll in Medicare within your IEP. COBRA will automatically terminate when you get Medicare anyway — federal rules prohibit duplicate coverage.

**Sequence summary:** Job ends → Elect COBRA if needed → Enroll in Medicare Part A+B immediately (don't wait for COBRA to end) → Pick Medigap/Part D → Let COBRA terminate or decline it

This is the section that should scare you into enrolling on time. These penalties are permanent, they compound, and there's no cap on how large they can get.

**Part B Late Enrollment Penalty**

For every full 12-month period you were eligible for Part B but didn't enroll (and didn't have qualifying employer coverage), your Part B premium increases by 10%. Permanently.

That 10-year scenario isn't hypothetical. I've seen people show up at SHIP counseling offices with decade-long gaps. The $202.90 they'd be paying becomes $405.80 — for life. At that rate, the penalty alone costs over $2,400 per year, year after year.

And here's the compounding problem: the penalty percentage is permanent, but it's applied to the current year's base premium, which increases over time. So the actual dollar penalty grows every year.

Part B penalties are assessed based on completed 12-month periods. Six months late? No penalty. Thirteen months late? 10% penalty. Twenty-five months late? 20% penalty. It's all-or-nothing at each 12-month mark.

**Part A Late Enrollment Penalty**

Most people get Part A free, so this rarely applies. But if you have to buy Part A and you don't enroll during your IEP, your Part A premium goes up 10% for twice the number of years you could have had Part A but didn't sign up. Two-year penalty duration for each year delayed.

Example: If you delayed Part A for 2 years, your premium ($565/month in 2026 if you have fewer than 30 quarters) goes up 20% ($565 × 1.20 = $678/month) and you pay that higher amount for 4 years.

**Part D Late Enrollment Penalty**

The Part D penalty applies if you go 63 or more consecutive days without Part D coverage or other creditable prescription drug coverage after your initial enrollment period.

'Creditable coverage' means coverage at least as good as standard Medicare drug coverage — most employer plans, VA drug coverage, and TRICARE qualify. If you're on an employer plan that includes creditable drug coverage, you don't need Part D until you leave that coverage.

The penalty is calculated as: 1% of the national base beneficiary premium × the number of months you didn't have coverage, rounded to the nearest $0.10.

The 2026 national base beneficiary premium is $38.99.

The Part D penalty is permanent (stays with you even if you switch plans) and adjusts when the base beneficiary premium changes annually.

Something a lot of people miss: if you don't take any prescriptions and don't think you need Part D, you might be tempted to skip it. Don't. Sign up for the cheapest Part D plan available in your area (sometimes $5-15/month) just to avoid accumulating penalty months. If you never fill a prescription, you barely spend anything. If you do eventually need drugs and you've been paying the penalty for years, you'll wish you hadn't tried to save $10/month.

**How to Appeal a Penalty**

You can appeal Part B and Part D penalties if you had creditable coverage and CMS doesn't have the documentation. The process is: 1. Request a reconsideration from CMS/SSA 2. Submit proof of coverage (Explanation of Benefits, certificate of creditable coverage from prior insurer, employer letter) 3. If denied, you can escalate to an Administrative Law Judge

Penalty appeals aren't always successful, but if you genuinely had coverage and the records weren't shared with CMS, it's worth pursuing.

If you're under 65 and on Medicare due to SSDI, your enrollment works differently from the age-65 path, and some of the rules are less intuitive.

**The 24-Month Wait** As covered above, you're automatically enrolled in both Part A and Part B after your 24th month of receiving SSDI benefits. The enrollment is automatic — you don't apply. Your Medicare card arrives in the mail. Coverage starts the first day of month 25.

During months 1-24 of SSDI, you have no Medicare. You need other coverage — either your employer's plan (if you're still in some employment situation), Medicaid, or a marketplace plan. This gap is one of the major policy failures in the Medicare system and it causes real harm to people with serious disabilities who can't access healthcare during the wait.

**IEP for Disabled Beneficiaries** Disabled beneficiaries under 65 also have an IEP — it's the 7-month period centered on month 25 (your Medicare start month). You can enroll in Part D and Medicare Advantage during this window.

**At Age 65** When a disabled Medicare beneficiary turns 65, they're already on Medicare — nothing changes in terms of eligibility. Their Medicare just transitions from disability-based to age-based. They do NOT lose and re-gain Medicare at 65. The coverage continues uninterrupted.

**Medigap Protections for Disabled Beneficiaries** Here's where it gets painful. In most states, insurance companies are not required to sell Medigap policies to people under 65 on Medicare due to disability. Some states have extended guaranteed-issue protections to disabled beneficiaries under 65, but most haven't. If you're under 65 on Medicare, check your state's rules — but prepare for the possibility that Medigap isn't available to you until you turn 65.

When you turn 65, you do get a full Medigap Open Enrollment Period — six months of guaranteed-issue rights from your 65th birthday. Use it. This is when you can get Medigap regardless of your health history.

**Part D for Disabled Beneficiaries** Part D enrollment rules and penalties apply the same way as for age-65 enrollees. If you didn't enroll when your Medicare started (month 25 of SSDI), you may be building a penalty.

**Working While Disabled** SSDI recipients can work under certain rules (Substantial Gainful Activity limits, Trial Work Period provisions) without immediately losing benefits. If you have a disability, are on SSDI, and are also working for an employer with 100 or more employees, there's a special rule: your employer plan is primary and Medicare is secondary for up to 30 months from when Medicare started. After 30 months, Medicare becomes primary regardless of employer size. This is different from the age-65 employer size rules and trips people up.

Federal employees and retirees have a unique situation because they have access to the Federal Employees Health Benefits Program — FEHB — which is one of the better employer health benefit programs in the country. The Medicare/FEHB interaction is genuinely confusing and the rules depend on whether you're still working or already retired.

**Still Working Federal Employees** If you're an active federal employee turning 65, you're in the same boat as any large employer: the federal government has well more than 20 employees, so your FEHB plan is primary and Medicare is secondary. You can delay Medicare Part B without penalty as long as you're actively employed and covered by FEHB.

Most active federal employees delay Part B because the combined FEHB premiums + Part B premium (currently $202.90/month) can be substantial, and FEHB alone provides solid coverage while you're working.

When you retire, you have an 8-month SEP to enroll in Part B.

**Retired Federal Employees** Here's where it gets more interesting. If you're already retired and covered by FEHB, and you're now turning 65 and enrolling in Medicare, here's what typically happens:

Medicare becomes primary. FEHB becomes secondary. Many FEHB plans actually waive some or all of their cost-sharing when Medicare is primary — meaning the combination can result in very low out-of-pocket costs for retirees. Some FEHB plans under a Medicare+FEHB combination function almost like supplemental insurance.

Many federal retirees find that having both Medicare Part A, Part B, and FEHB is actually a good deal because the FEHB waiver provisions reduce their cost-sharing to near-zero. Some FEHB plans are even designed specifically with Medicare as primary in mind.

However, you're paying both premiums. Part B at $202.90/month plus your FEHB share. For some people in excellent health who rarely use healthcare, this feels wasteful. For people with chronic conditions or significant health needs, the cost-sharing reduction from FEHB waiver provisions usually makes it worthwhile.

**Part D and FEHB** Most FEHB plans provide prescription drug coverage that qualifies as creditable coverage for Medicare Part D purposes. This means federal employees and retirees on FEHB typically don't need Part D and don't face Part D late penalties.

Verify this with your specific FEHB plan annually. Your plan's Annual Notice of Change will state whether its drug coverage is creditable. Keep that notice.

**Should Federal Retirees Take Part B?** This is genuinely debated among SHIP counselors and benefits specialists. The general answer is yes, because the long-term cost of avoiding Part B penalties if your circumstances change, plus the value of having Medicare primary with FEHB supplemental, usually outweighs the monthly premium. But there are edge cases where declining Part B makes financial sense.

If you're a federal retiree on FEHB, don't make this decision based on a generic guide (including this one). Contact your agency's benefits office or OPM, and consider a consultation with a SHIP counselor. The FEHB/Medicare interaction is complex enough that individual circumstances matter.

Deciding you want out of Medicare Advantage and back to Original Medicare is more common than the industry would like to admit, and the process has real complications around Medigap coverage that you need to understand before you make the switch.

**When You Can Switch**

You have three opportunities to leave Medicare Advantage:

1. Annual Enrollment Period (October 15 - December 7): Switch for following January 1 coverage.

2. Medicare Advantage Open Enrollment Period (January 1 - March 31): Switch once, effective first of the following month.

3. Special Enrollment Period: If a qualifying event applies (moving, plan termination, etc.).

Outside these windows, you're stuck in your plan until the next opportunity.

**The Medigap Problem**

Here's the part that surprises people. When you switch back to Original Medicare, Original Medicare has significant cost-sharing: the Part B deductible ($283/year in 2026), 20% coinsurance on most services with no cap, and the Part A deductible ($1,736 per benefit period). Without a Medigap policy, these costs can be enormous if you get seriously ill.

But here's the catch: except in specific protected circumstances, Medigap insurers can use medical underwriting in most states. They can look at your health history, charge you more based on pre-existing conditions, or reject you entirely.

The protected circumstances where you have guaranteed-issue rights for Medigap:

If none of those apply and you've been on Medicare Advantage for several years, you're subject to medical underwriting. If you have diabetes, heart disease, cancer history, or other serious conditions, you may be denied Medigap or charged significantly more.

A few states have stronger protections. California, Connecticut, Maine, Massachusetts, New York, Washington, and a handful of others have continuous open enrollment or birthday rules for Medigap. If you're in one of those states, your options are better. Check your state's rules.

**The Practical Decision Tree**

If you're within your first 12 months on Medicare Advantage and it's not working for you, switch back now and use your guaranteed-issue Medigap rights.

If you've been on Medicare Advantage for years and are in good health, you can likely still get Medigap through underwriting but compare plans and rates carefully before making the jump.

If you've been on Medicare Advantage for years and have significant health conditions, switching to Original Medicare without Medigap may leave you exposed to large cost-sharing. Run the numbers carefully. MA's annual out-of-pocket maximum (must be no more than $9,350 for in-network costs in 2026) may actually protect you better than Original Medicare without a Medigap policy.

**How to Actually Disenroll**

Call your Medicare Advantage plan directly and tell them you want to disenroll. They're required by law to process your request. You can also call 1-800-MEDICARE (1-800-633-4227) and they can help process the disenrollment. Do NOT just stop paying premiums — that can create a mess.

When you disenroll, CMS will revert you to Original Medicare. Your Part D coverage from your MA plan terminates — you'll need to enroll in a standalone Part D plan if you don't have other drug coverage, and you need to do that within 63 days to avoid starting the Part D penalty clock.

Three ways to enroll. All work. Pick whichever matches your comfort level.

**Option 1: Online at SSA.gov**

Go to SSA.gov/benefits/medicare. You can apply online 24 hours a day, 7 days a week. The whole process takes about 10-15 minutes if you have your information ready.

What you'll need: — Social Security number — Date and place of birth — Citizenship status — Current address — Direct deposit information (if you want your Part B premium deducted from Social Security) — Information about current or recent employer insurance (if applicable)

The online application gives you a confirmation number. Save it. You'll also get a letter from SSA within 2-4 weeks confirming your enrollment.

Note: The online application handles enrollment in Original Medicare (Part A and Part B) only. For Part D and Medicare Advantage, go separately to Medicare.gov/plan-compare after you have your Medicare number.

**Option 2: By Phone**

Call Social Security at 1-800-772-1213. The line is open Monday through Friday, 8am to 7pm in your local time zone. Wait times can be long — calling right when they open or on Wednesdays/Thursdays tends to be shorter.

For Railroad Retirement beneficiaries: call the RRB at 1-877-772-5772.

Phone enrollment is good if you have questions or unusual circumstances — the representative can walk you through edge cases like working past 65, disability status, or late enrollment situations.

**Option 3: In Person at Your Local SSA Office**

Find your local office at SSA.gov/locator. Make an appointment — seriously, make an appointment. Walk-in wait times at some offices are measured in hours.

In-person is best for: — Complex situations (disability, ESRD, appeals) — People who prefer face-to-face — Situations where you need to submit physical documents

**After You Apply: What Happens Next**

Part A is usually effective immediately or on your planned start date. Your Medicare card arrives in the mail within about 4-6 weeks of applying.

Once you have your Medicare number (it's on the card — a combination of letters and numbers, not your Social Security number), you can use it to enroll in Part D and Medicare Advantage at Medicare.gov/plan-compare.

If you're enrolling Part D or Advantage separately, do that promptly. Your Part A/B effective date starts your Part D enrollment clock — if you delay Part D enrollment, you may start accumulating penalty days.

**If You Want to Decline Part B**

If you're auto-enrolled but want to delay Part B (because you have qualifying employer coverage), you'll receive a notice with instructions for declining. You can also call 1-800-MEDICARE or contact SSA to put the declination on record. Don't just let Part B lapse — actively decline it and document the reason.

Auto-enrollment is real, it's common, and it can catch people off guard — both in good ways and bad.

**Who Gets Auto-Enrolled**

If you're receiving Social Security retirement benefits or Railroad Retirement Board benefits at least four months before you turn 65, CMS automatically enrolls you in both Part A and Part B. Your Medicare card arrives in the mail about three months before your 65th birthday.

Similarly, if you've been on SSDI for 24 months, you're automatically enrolled in both Part A and Part B at month 25. No application needed.

**What Auto-Enrollment Covers**

Auto-enrollment covers Part A and Part B only. It does NOT automatically enroll you in Part D, Medicare Advantage, or Medigap. You still need to choose and enroll in those separately during your IEP.

**If You Don't Want Part B**

Auto-enrollment includes Part B, which means the $202.90/month premium will be deducted from your Social Security check unless you decline it. If you have qualifying employer coverage and don't want Part B, you need to actively opt out. The Medicare card you receive will have instructions, or you can call SSA.

Missing this is a common problem. People see the deduction from their Social Security, assume it's automatic and correct, and keep paying for Part B when they didn't need it and could have declined it for years. Conversely, some people assume they don't need to do anything and then discover they were never auto-enrolled because they weren't on Social Security yet — and they've been accruing penalty months without coverage.

**Early Social Security and Auto-Enrollment**

If you took Social Security benefits early (at 62, 63, or 64), you will be auto-enrolled in Medicare at 65 without doing anything. Your benefits were already running; the Medicare enrollment just kicks in at 65.

**The Part B Opt-Out Timing**

If you're auto-enrolled and want to decline Part B, you need to send back the opt-out form that comes with your Medicare card or call SSA before your coverage starts. If you miss this and Part B activates, you'll need to request termination — which goes retroactive to when your employer coverage started, but involves some administrative work.