Turning 65 as a Military Retiree: The Timeline

Last reviewed: 2026-08-11

Turning 65 as a military retiree comes with a real deadline: Medicare Part B. Miss it, and TRICARE For Life (TFL) does not start the way it should. Here is the timeline, month by month, so nothing slips.

The window: 7 months, centered on your birthday

Medicare’s Initial Enrollment Period (IEP) runs for seven months: three months before the month you turn 65, your birthday month itself, and three months after. That window is not unique to military retirees, it is how Medicare enrollment works for everyone, but for retirees it carries extra weight, because TFL depends entirely on getting Part B active on time.

Why Part B is the one step that matters

TFL is not something you apply for. It attaches automatically the moment you have both Medicare Part A and Part B active. Part A is usually premium-free, since you paid into it through payroll taxes while you served. Part B carries a monthly premium, and it is the one piece of this whole system that requires action from you.

If you let your IEP pass without enrolling in Part B, you delay TFL along with it, and you may face a Part B late-enrollment penalty on top of that. There is no separate TFL enrollment step waiting for you to catch up. TFL simply will not start until Part B does.

What happens to your current TRICARE plan

TRICARE Prime and TRICARE Select end earlier than most retirees expect: on the last day of the month before your 65th birth month, for you and your spouse individually. That is not the same as your birthday. TFL takes over once your Medicare Part A and Part B are both active, and if your Part B start date lines up right, the handoff is seamless. If it does not, there is a real window with no TRICARE and no Medicare in place. You do not fill out a TFL application. You do need to keep your information current in DEERS, the Defense Enrollment Eligibility Reporting System, since that is what confirms your continued TRICARE eligibility.

Your pharmacy benefit does not interrupt during this transition. Coverage through the TRICARE Pharmacy Program, administered by Express Scripts, continues without a separate action on your part.

The month-by-month checklist

6 months before your 65th birthday: Start paying attention. Confirm the month your Initial Enrollment Period begins, three months before your birthday month, and mark your calendar.

3 months before: Your IEP opens. This is the only window that guarantees a gap-free start: sign up for Medicare Part A and Part B anytime in these 3 months, and coverage begins the first day of your birthday month, exactly when your TRICARE Prime or Select coverage runs out.

Your birthday month: If you have not enrolled yet, understand what waiting costs you. Medicare’s rule is firm: sign up during your birthday month, and Part B (and TFL with it) does not start until the first day of the following month, not on your actual birthday. Since your TRICARE Prime or Select coverage already ended the month before, this leaves a real gap with no TRICARE and no Medicare in place. Enroll immediately to keep that gap as short as possible, and check that your military ID and DEERS information are current while you are at it.

1 to 3 months after your birthday: This is the tail end of your IEP, and the same rule applies: your Part B and TFL coverage start the first day of the month after you sign up, never retroactively to your birthday. The gap that opened when your TRICARE ended keeps growing the longer you wait. Enroll as early in this window as you can.

After your IEP closes: If you missed the window entirely without a valid excuse, you are looking at the General Enrollment Period, January 1 through March 31 each year, with coverage starting the following month and a possible late penalty attached. Avoid this by acting during your IEP.

If you are still working past 65

If you are still employed and covered by a current employer’s group health plan when you turn 65, you can delay Part B without a penalty, using a Special Enrollment Period that gives you 8 months after your employment or employer coverage ends to sign up. This is standard Medicare policy, not something specific to military retirees. Here is the part that catches retirees off guard: during that delay, you do not have TRICARE coverage as a backup. TRICARE Prime and TRICARE Select already ended on their usual schedule, and TFL does not start until Part B does, so for as long as you delay Part B, your employer’s plan is your only coverage. TFL, and your TRICARE eligibility along with it, comes back once you enroll in Part A and Part B.

Spouses run on their own clock

Your spouse’s TRICARE and Medicare timeline is not tied to yours. If your spouse is younger than you, they keep their current TRICARE plan, Select or Prime, until they approach their own 65th birthday. At that point, they go through this same seven-month window and the same Part B decision, independently of whatever you already did.

The bottom line

The only hard deadline in this entire process is enrolling in Medicare Part B, and the only window that guarantees a gap-free start is the 3 months before your birthday month. Everything else, TFL attaching, your pharmacy benefit continuing, your old TRICARE plan converting, happens automatically once Part B is active. Mark the seven-month window, enroll in the first 3 months rather than waiting, and keep DEERS current, and the rest of this transition takes care of itself.

Not sure what applies to you? Take the two-minute Decision Guide.