Medicare Federal Retiree Timeline: When to Enroll and What to Coordinate

Federal Retirees Face a Different Medicare Decision Than Everyone Else

Most Americans hit 65 and enroll in Medicare because they need it — their employer coverage ends. Federal retirees are different. FEHB continues into retirement, covers most of the same things Medicare does, and doesn't require Part B. So the question isn't just "when do I sign up" but "do I need to, and what happens if I don't?"

The answer depends on whether you're a standard federal retiree, a postal worker under PSHB, or a CSRS retiree coordinating pension and Social Security. Here's the timeline, broken by situation.

The Universal Part: Medicare Part A

Nearly all federal employees qualify for premium-free Medicare Part A (Hospital Insurance) at age 65 if they have 40 or more quarters of Medicare-covered employment. Since FERS employees have paid Medicare taxes throughout their careers, Part A is automatic for them.

CSRS employees are trickier. If your entire career was under CSRS before 1983, you may not have enough Medicare-covered quarters for premium-free Part A. You can purchase Part A — $518/month in 2026 with fewer than 30 quarters — but that's a substantial cost most people don't anticipate.

Timeline: If you're collecting Social Security, Part A enrollment is automatic at 65. If you're not yet collecting, you need to sign up during your Initial Enrollment Period — the 7-month window that starts 3 months before your 65th birthday month.

Standard Federal Retirees (FEHB): Part B Is Optional

If you retired under FEHB (not PSHB), Medicare Part B is genuinely optional. FEHB is creditable coverage — it doesn't create a late enrollment penalty for Part B if you delay past 65. You can enroll in Part B at any time during a Special Enrollment Period (SEP) and won't pay the 10%-per-year penalty that applies to the general public.

Why some retirees still want Part B: With both FEHB and Medicare, Medicare becomes the primary payer and FEHB becomes secondary. This coordination eliminates or dramatically reduces out-of-pocket costs — copays, deductibles, and coinsurance that FEHB alone would leave you responsible for. Many FEHB plans waive copays entirely when Medicare is the primary payer.

The cost: The standard Part B premium is $202.90/month in 2026. If your modified adjusted gross income exceeds $109,000 (single) or $218,000 (married filing jointly), you'll pay an Income-Related Monthly Adjustment Amount (IRMAA) on top of the standard premium. The highest IRMAA tier starts at $500,000/$750,000 and pushes the monthly Part B premium above $600.

Timeline for standard FEHB retirees:

Postal Workers (PSHB): Part B Is Mandatory

The Postal Service Health Benefits program, which replaced FEHB for postal employees and retirees on January 1, 2025, requires Medicare Part B enrollment for anyone entitled to Medicare Part A. This is not optional — if you don't enroll in Part B, you lose your PSHB health coverage.

Who must enroll: Any postal annuitant (or their Medicare-eligible spouse/dependent) who becomes entitled to Medicare Part A. "Entitled" means you're eligible and at least 65 — or under 65 with a qualifying disability.

Exemptions: Postal annuitants who retired on or before January 1, 2025, and active postal employees who were age 64 or older as of January 1, 2025, are exempt from the mandatory Part B requirement. They can keep PSHB without Part B.

Timeline for postal retirees under PSHB:

Part D (Prescription Drug Coverage)

Most FEHB and PSHB plans include prescription drug coverage that's considered "creditable" — meaning it's at least as good as Medicare Part D. As long as your plan is creditable, you don't need to enroll in a standalone Part D plan and won't face the late enrollment penalty.

Your FEHB or PSHB plan sends you a creditable coverage notice annually, usually during Open Season. Keep these notices — they're your proof if you ever need to enroll in Part D later.

Exception: If you drop FEHB/PSHB or switch to a plan that doesn't have creditable drug coverage, you have 63 days to enroll in Part D or face a permanent penalty of 1% of the national base premium ($38.99/month in 2026) for each month you were uncovered.

Medigap (Supplement) Plans

Federal retirees rarely need Medigap policies because FEHB or PSHB already acts as secondary coverage when paired with Medicare. Buying a Medigap plan on top of FEHB and Medicare means paying three premiums for coverage that largely overlaps. In most cases, FEHB-plus-Medicare coordination provides more comprehensive protection than Medicare-plus-Medigap alone.

CMS Forms You'll Need

Two forms matter for most federal retirees:

• CMS-40B (Application for Enrollment in Medicare Part B): Filed at your local Social Security office or online at ssa.gov. If you're enrolling during a SEP based on employer coverage, you'll also need CMS-L564.
• CMS-L564 (Request for Employment Information): Your agency or OPM certifies that you had creditable employer-based coverage. Required when applying for Part B during a Special Enrollment Period to waive the late penalty.

Building This Into Your Retirement Countdown

Medicare coordination isn't a one-time decision — it unfolds over the 12 months before and after you turn 65. The Federal Retirement Countdown Checklist integrates Medicare enrollment deadlines into the overall retirement timeline so the FEHB/PSHB coordination, Part B enrollment, and premium budgeting happen alongside your annuity application and TSP planning, not as an afterthought.