Of the two Medicare decisions a federal retiree has to make, Part A is the easier one — and the one most retirees benefit from getting done automatically. For the vast majority of federal retirees, the right answer is: enroll in Medicare Part A as soon as you are eligible. The premium is free for almost everyone who has at least 40 Social Security credits, the coverage is generous, and the interaction with FEHB in retirement is overwhelmingly favorable.

The exceptions exist. They are real. They are also narrow, and most federal retirees do not fall into them. The most common exception involves a Health Savings Account, and even there the math often favors enrollment once the HSA is no longer being funded.

What Medicare Part A actually covers.

Part A is the inpatient side of Medicare. It covers hospital stays, skilled nursing facility care after a qualifying hospital admission, hospice care, and some home health services. For a federal retiree with FEHB, Part A is the layer that pays the hospital bill first when Medicare becomes the primary payer, with FEHB picking up most or all of what Medicare leaves behind.

Part A is premium-free for anyone who has at least 40 Social Security credits (roughly ten years of work) — which is essentially every career federal employee. There is no reason to decline free inpatient coverage in retirement unless there is a specific reason to do so.

When to enroll: the default answer.

The cleanest enrollment path for a federal retiree is to take Part A during the Initial Enrollment Period (IEP) that begins three months before the month you turn 65 and ends three months after. For most federal employees who retire after 65, the relevant window is the Special Enrollment Period (SEP)triggered by the loss of active employer coverage through EGHP — generally an eight-month window from the retirement date.

If you are already 65 and on Medicare when you retire from federal service, you are already enrolled in Part A. If you retired before 65 and are carrying FEHB into retirement, you have an eight-month SEP from your retirement date to enroll when you turn 65.

If you are 65 or older and still working, the IEP / SEP timing interacts with your active employment in ways that deserve a careful look. Talk to your HR office or a benefits advisor who understands both FEHB and Medicare before making the call.

The HSA exception that almost everyone worries about.

The one situation in which delaying Part A is a real consideration is when a federal retiree is funding a Health Savings Account. Once you enroll in any part of Medicare (including Part A), you can no longer contribute to an HSA. That alone can make a federal retiree pause.

The pause is often wise, but only briefly. HSA contributions stop the month you enroll in Medicare, but the IRS allows you to delay Part A enrollment up to six months retroactively if you are 65 or older and covered by an HSA-compatible employer plan. Once you retire, the HSA math changes — you can still use the balance, but you cannot contribute new dollars. Most retirees in this situation enroll in Part A at retirement or shortly after.

How Part A interacts with FEHB.

When a federal retiree has both Part A and FEHB, Medicare becomes the primary payer for inpatient claims and FEHB becomes the secondary payer. The retiree’s out-of-pocket cost for hospital stays drops sharply, often to zero, depending on the FEHB plan. The combination is one of the best retiree health coverage arrangements available anywhere in the United States.

Without Part A, FEHB remains the primary payer for inpatient claims. That is a workable arrangement, but it is more expensive than the Medicare-primary arrangement, and the retiree who has both programs on the table is leaving real money on the hospital side of the ledger.

What to do in the months before you turn 65.

If you are a federal employee within a year of 65, the practical steps are:

  • Confirm your Social Security earnings record. The 40-credit test for premium-free Part A is rarely a problem for career federal employees, but it is worth verifying.
  • Decide whether you want Part A active the day you turn 65 or delayed. The default is to enroll; the exception is the HSA.
  • Compare your current FEHB plan against the Medicare-friendly FEHB plans available in your zip code. The plan that was right at 60 may not be the best plan at 65.
  • Apply for Part A through Social Security three months before your 65th birthday month (or use the SEP at retirement if you are 65+).

For more on the larger Part B decision, read what Medicare Part B is, and whether it is mandatory.