You are not legally required to go on Medicare at 65. But for most people the practical answer is yes, because skipping enrollment without a narrow set of qualifying reasons triggers premium penalties that last the rest of your life and can strip you of other benefits you’re counting on. The one broadly available reason to delay is active coverage through a current employer with 20 or more employees.1Medicare. Avoid Late Enrollment Penalties
You May Already Be Enrolled Without Doing Anything
If you’ve been collecting Social Security or Railroad Retirement Board benefits for at least four months before your 65th birthday, the decision is largely made for you. Medicare enrolls you automatically in Part A (hospital) and Part B (medical), and your card arrives in the mail before you turn 65. Coverage starts the first day of your birthday month, or the month before if your birthday falls on the first.2Social Security Administration. Publication 05-10043 – Medicare
Part A is premium-free for anyone with roughly ten years of Medicare-taxed work (40 quarters). Part B costs $202.90 a month in 2026 for most people, more for higher earners.3Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles You can decline Part B by following the instructions that come with the card. Declining without qualifying coverage sets up a penalty later.
If you’re not yet drawing Social Security, no one signs you up. You apply during your Initial Enrollment Period, a seven-month window that starts three months before your birthday month and ends three months after.4Medicare. When Does Medicare Coverage Start
When It’s Safe to Delay: Active Coverage From a Large Employer
Working past 65 with health insurance from a current employer of 20 or more people is the cleanest reason to postpone. That employer plan pays first and Medicare pays second, and you keep the right to enroll in Part B later without penalty.5Medicare. Who Pays First The same rule applies if you’re covered through a spouse who is actively working at a large employer.
When the job or the coverage ends, whichever comes first, an eight-month Special Enrollment Period opens for Part B.6Medicare. Working Past 65 You and your employer will file Form CMS-L564 to document the qualifying coverage.7Medicare. Enrollment Forms
Miss that eight-month window and the price is steep. You wait for the General Enrollment Period (January 1 through March 31), coverage doesn’t begin until the month after you enroll, and the lifetime Part B penalty kicks in.4Medicare. When Does Medicare Coverage Start
Coverage That Does Not Let You Skip Medicare
Several kinds of insurance feel like they should qualify but don’t.
Small employer plans. If your employer has fewer than 20 employees, Medicare becomes the primary payer at 65. The employer plan expects Medicare to pay first, and it may deny claims Medicare would have covered. Skipping enrollment leaves you paying those bills yourself.8Centers for Medicare & Medicaid Services. Small Employer Exception
COBRA and retiree plans. Neither counts as active employer coverage. Both pay after Medicare, so if you aren’t enrolled in Part B, they cover very little. Relying on COBRA or a retiree plan at 65 is not a reason to delay Medicare; it’s a reason to enroll on time.5Medicare. Who Pays First
ACA Marketplace plans. A Healthcare.gov plan doesn’t qualify either. Once you become eligible for premium-free Part A, you lose access to advance premium tax credits and other Marketplace savings, and subsidies received after that point may need to be repaid at tax time.9Centers for Medicare & Medicaid Services. Transitioning From Marketplace to Medicare Coverage Insurers aren’t obligated to renew Marketplace coverage for someone on Medicare, and you’d pay full price if they did.
Military and VA Situations
TRICARE For Life, the supplemental coverage for TRICARE-eligible retirees, only works if you have both Part A and Part B. With Part B, TRICARE typically leaves you with nothing out of pocket for services both programs cover. Without Part B, TRICARE For Life doesn’t activate at all.10TRICARE. TRICARE For Life The rule applies to retirees living overseas too, even though Medicare itself doesn’t provide coverage outside the country.
CHAMPVA has the same structure. If you qualify for premium-free Part A, you must enroll in Part B and stay enrolled to keep CHAMPVA benefits. The one carve-out: if you’re over 65 and were never eligible for premium-free Part A, CHAMPVA doesn’t require Part B.11Department of Veterans Affairs. CHAMPVA Guidebook
VA healthcare works differently. Medicare enrollment has no effect on the VA benefits you’re entitled to, and the VA doesn’t require you to enroll. The VA still encourages veterans to sign up when eligible, because Medicare covers care at non-VA hospitals and doctors and acts as a backup if VA access changes. You can’t use both programs for the same visit; each time you seek care, you use one or the other.12Veterans Affairs. VA Health Care and Other Insurance
What Skipping Medicare Actually Costs
If you delay without a qualifying reason and later change your mind, three separate penalties can hit.
Part B. Your monthly premium goes up 10 percent for each full 12-month period you could have had Part B but didn’t. You pay that surcharge for as long as you have Part B, which in practice means for life.1Medicare. Avoid Late Enrollment Penalties
Part D. If you go without creditable prescription drug coverage for 63 days or more after becoming eligible, you owe 1 percent of the national base beneficiary premium ($38.99 in 2026) for every full month you were uncovered, added to your Part D plan premium permanently. Twenty-four uncovered months translates to roughly $9.36 extra a month, forever.13Medicare. How Much Does Medicare Drug Coverage Cost If your employer or union provides drug coverage, they must send an annual notice stating whether it counts as creditable. Save those notices.
Part A. Most people get Part A free. If you don’t (fewer than 40 quarters of Medicare-taxed work) and you enroll late, the Part A premium rises 10 percent, and you pay the higher amount for twice the number of years you delayed.1Medicare. Avoid Late Enrollment Penalties
On top of the penalties, missing your enrollment windows creates a coverage gap. The General Enrollment Period runs January 1 through March 31, and coverage begins the month after you sign up.4Medicare. When Does Medicare Coverage Start
The HSA Timing Trap
One reason people actively want to skip Medicare at 65 is to keep contributing to a Health Savings Account. Enrollment in any part of Medicare, including premium-free Part A, ends your eligibility to make new HSA contributions. Contributions made after your Medicare effective date become excess contributions subject to a 6-percent excise tax.14Internal Revenue Service. Instructions for Form 8889
The trap is that Part A is backdated up to six months when you apply for Social Security after age 65. Contributions you made in what you thought were eligible months can retroactively become excess. The 2026 HSA limits are $4,400 for self-only coverage and $8,750 for family coverage, and you have to pro-rate for the months before Medicare starts.15Internal Revenue Service. Expanded Availability of Health Savings Accounts Under the OBBBA Stopping contributions at least six months before you apply for Medicare or Social Security is the safe move. Existing HSA funds remain available for qualified medical expenses, including Medicare premiums, after you enroll; the restriction is only on new deposits.
How to Decide
The choice comes down to what coverage you have on your 65th birthday. Active coverage through a current employer of 20 or more, held by you or an actively working spouse, lets you postpone Part B safely and use the eight-month Special Enrollment Period later. Anything else (small-employer coverage, COBRA, a retiree plan, a Marketplace plan, or nothing) means enrolling during your seven-month Initial Enrollment Period is almost always the right call. TRICARE For Life and CHAMPVA beneficiaries who qualify for premium-free Part A need Part B to keep those benefits at all. VA users don’t, but usually benefit from enrolling anyway.