Written by If you or your spouse retired from the military, turning 65 isn’t just a Medicare milestone. It’s the moment your TRICARE coverage changes shape, and the single most important step, signing up for Medicare Part B, has a timeline that’s easy to get wrong. Here’s the sequence that keeps coverage uninterrupted.
What Actually Changes at 65
Before 65, many military retirees and their families use TRICARE Prime or TRICARE Select as their primary coverage. At 65, Medicare becomes primary and TRICARE For Life (TFL) steps in as the second payer. For most people, that transition is automatic on the TRICARE side, but only if Medicare Part A and Part B are both in place. TRICARE’s own guidance is blunt about this: to keep your TRICARE benefits at 65, you must have Medicare Part A and Part B, or proof that you aren’t eligible for premium-free Part A.
Most people qualify for premium-free Part A and enroll in it automatically if they’re already receiving Social Security. Part B is different. It carries a monthly premium and it generally isn’t automatic unless you’re already receiving Social Security benefits, which is exactly why it’s the step that trips people up. For the underlying rules, see our guide to Medicare and TRICARE For Life.
The Timeline, Step by Step
- About 3 months before your birthday month: your Medicare Initial Enrollment Period opens. This is the window to sign up for Part B so it starts on time.
- No later than 2 months before you turn 65: TRICARE advises signing up for Part B by this point if you’re eligible for premium-free Part A, to avoid a break in coverage. Our guide to applying for Medicare online walks through the process.
- The month you turn 65: Part A and Part B take effect. TFL coverage starts automatically on the day you have both.
- Around the same time: your Medicare card arrives, and your military ID card is typically due for renewal. TRICARE says to renew it when you get your Medicare card.
- Ongoing: keep paying your Part B premium on time. A lapse in Part B means a lapse in TRICARE For Life.
If you sign up for Part B during the first three months of your Initial Enrollment Period, it generally starts on the first day of the month you turn 65. Wait until your birthday month or later, and your start date slides back, which can open a gap. Our Turning 65 guide covers the full seven-month window.
You Don’t Enroll in TFL, But Your DEERS Record Matters
There’s no separate application for TRICARE For Life. Coverage begins automatically once Medicare Part A and Part B are both effective. What does need your attention is your record in the Defense Enrollment Eligibility Reporting System, or DEERS. That’s the system that confirms who’s eligible, and outdated information after a marriage, divorce, or change in a dependent’s status is one of the most common reasons coverage doesn’t line up the way someone expects. Check it before you turn 65, not after. If you ever find that your TRICARE coverage isn’t showing up the way you expected after your Medicare start date, the fix usually starts with confirming that both parts of Medicare are effective on the dates you think they are and that DEERS reflects them. Catching a mismatch in the first month is far easier than untangling it a year later after several claims have already been denied.
What If You Aren’t Eligible for Premium-Free Part A?
Some people don’t have enough work history to qualify for premium-free Part A. TRICARE has a separate path for that situation: beneficiaries who aren’t eligible for premium-free Part A can generally keep TRICARE Prime or Select past 65, with the right documentation on file. If that might describe you or your spouse, don’t assume the standard timeline applies. Confirm the details with TRICARE directly, because the rules for this group differ from the ones above.
What Happens If You Miss the Window
If Part B isn’t in place when it should be, your TRICARE For Life coverage doesn’t begin until it is, and that can leave a real gap. Signing up for Part B after your Initial Enrollment Period generally means waiting for the next General Enrollment Period, with the possibility of a permanent late-enrollment penalty added to your Part B premium. For someone depending on TFL as their supplemental coverage, that’s a costly mistake to make by accident. It’s also why this is one deadline worth setting a calendar reminder for well in advance.
After Part B: Original Medicare or Medicare Advantage?
Once Part B is in place, there’s still a choice to make, and it matters for a TRICARE beneficiary in a way it doesn’t for civilians. With Original Medicare, claims cross over to TRICARE For Life automatically. With a Medicare Advantage plan, they don’t, and you may need to file claims yourself. Neither is wrong, but you should choose with that difference in mind. We explain it in detail in our post on TRICARE For Life with a Medicare Advantage plan.
Prescriptions are simpler. TRICARE’s pharmacy program counts as creditable drug coverage, so most TFL beneficiaries don’t need a separate Part D plan and won’t face a late-enrollment penalty as long as they keep their TRICARE coverage.
Spouses and Survivors Run Their Own Clocks
TRICARE eligibility extends to qualifying spouses and survivors, but each person reaches Medicare on their own birthday, not the retiree’s. A retiree who turned 65 three years ago and a spouse turning 65 this year are on two different timelines, and the spouse needs Part B in place on their own schedule to keep their own TRICARE coverage. This is one of the most common places a household gets caught off guard: one person did everything right years ago, and the other assumed the first person’s enrollment covered both.
If You’re Still Working or Living Overseas
Two situations change the standard picture. If you’re still working past 65 with employer coverage, Medicare’s timing rules are different, and how TRICARE fits in depends on your circumstances. Start with our guide to Medicare while still working past 65, then confirm the TRICARE side directly.
If you live overseas, the Part B requirement still applies even though Medicare generally doesn’t cover care outside the United States. Part B is what keeps you eligible for TRICARE, and abroad, TRICARE For Life becomes the primary payer for TRICARE-covered services. Many retirees are surprised to learn they need to keep paying a Medicare premium for coverage they can’t use overseas, but dropping it can cost them TRICARE entirely.
A Simple Checklist for the 90 Days Before You Turn 65
- Check your DEERS record and correct anything that’s out of date.
- Confirm whether you’re eligible for premium-free Part A.
- Sign up for Part B early in your Initial Enrollment Period, and well before your 65th birthday month.
- Decide between Original Medicare and Medicare Advantage, knowing how claims differ for TRICARE beneficiaries.
- Set up automatic payment for your Part B premium so it can never lapse by accident.
- Plan to renew your military ID card when your Medicare card arrives.
Part B Costs and Why Income Matters
Because Part B is the only premium you pay to keep TFL active, it helps to know what it costs and how it’s set. Most people pay the standard Part B premium, but higher-income households pay more through an income-related surcharge called IRMAA. If your income is high, or if you’ve recently had a one-time spike like a home sale, read our explainer on IRMAA. If you’re not yet receiving Social Security, our guide to setting up Medicare Easy Pay helps you pay premiums on time so there’s no accidental lapse.
Frequently Asked Questions
When should I sign up for Part B if I’m on TRICARE?
If you’re eligible for premium-free Part A, TRICARE advises signing up no later than two months before you turn 65, which generally means doing it during the first part of your Initial Enrollment Period.
Do I need to apply for TRICARE For Life?
No. Coverage starts automatically on the day you have both Medicare Part A and Part B, as long as your DEERS record is current.
What if I forget to enroll in Part B?
Your TRICARE For Life coverage doesn’t start until Part B does, and signing up late can mean waiting for the General Enrollment Period and paying a permanent late penalty. It’s worth setting a reminder well before your 65th birthday.
Does it matter whether I choose Original Medicare or Medicare Advantage?
It can. Original Medicare claims cross over to TRICARE automatically, while Medicare Advantage claims don’t, so you may need to file them yourself. See our post on TRICARE For Life with Medicare Advantage.
Approaching 65 with TRICARE and want to get the timing right? Reach out to our Medicare team, by phone or video wherever you live. There’s no cost and no obligation. We’re an independent agency, not affiliated with TRICARE or the Department of Defense, and TRICARE’s own website is the authority on your specific eligibility.
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