Glossary
Initial Enrollment Period (IEP)
The 7-month window around your 65th birthday when you first sign up for Medicare Parts A and B without penalty.
Also known as: IEP, Initial Enrollment, Initial Enrollment Period for Medicare
Quick answer
Your Initial Enrollment Period is a 7-month window: the 3 months before, the month of, and the 3 months after your 65th birthday month. It's your first opportunity to enroll in Medicare Parts A and B (and optionally Part D or a Medicare Advantage plan). Coverage start dates depend on when within the window you enroll.
Why it matters
IEP is the only enrollment window that guarantees no late-enrollment penalty AND no gap in coverage. Enrolling in the first three months means Medicare starts the first day of your birthday month. Waiting until the last three months delays coverage by a month or more.
Why this matters at age 65
For a retired service member transitioning to TFL, this window is everything. TFL only activates the day BOTH Part A and Part B are effective. Enroll early in your IEP so Medicare A and B begin the first of your birthday month — that's the only way to guarantee zero break in coverage between TRICARE Prime/Select and TFL.
When you'll encounter it
Exactly once, around your 65th birthday. Set a calendar reminder for 4 months before your 65th birthday — that's when you can file with SSA.
Impact on Medicare
Defines when your Parts A and B become effective. Enrolling in months 1–3 before your birthday month → coverage on the first of your birthday month. Enrolling in your birthday month → coverage the following month. Enrolling in months 5–7 → coverage delayed up to 3 months.
Impact on TRICARE For Life
Critical. TFL activates the day Medicare A and B both become effective. Missing the early portion of your IEP creates a gap between TRICARE Prime/Select (which terminates at 65) and TFL — leaving you uninsured for civilian care during that gap.
Impact on Medicare Advantage
Your Initial Coverage Election Period for Medicare Advantage and Part D mirrors the IEP. You can join an MA plan during the same 7-month window without a Special Enrollment Period.
VA Healthcare considerations
VA Healthcare enrollment is not affected by your Medicare IEP. But declining Part B during IEP because 'I have the VA' terminates your TFL forever and triggers permanent late penalties if you ever re-enroll. Use IEP to lock in Part B even if you plan to rely primarily on VA.
Military-specific context
Medicare uses your actual 65th birthday, not your military retirement date, to define IEP. If you were born on the first of the month, Medicare considers you 65 the prior month — your IEP shifts one month earlier.
Common misconceptions
- "I can sign up anytime once I'm 65." — Outside IEP you can only sign up during the General Enrollment Period (Jan 1 – Mar 31), and you'll likely owe permanent late penalties.
- "Social Security will enroll me automatically." — Only if you're already receiving SS or RRB benefits before 65. Otherwise you must actively enroll.
- "TRICARE will tell me when to sign up." — TRICARE does not send IEP reminders. The responsibility is entirely on you.
Common mistakes to avoid
- Waiting until the month of the 65th birthday to file — guarantees a one-month coverage gap.
- Declining Part B because of TRICARE or VA — terminates TFL and creates permanent penalties.
- Assuming the spouse's IEP is the same as the sponsor's — each beneficiary has their own IEP based on their own birthday.
- Not verifying DEERS reflects Medicare dates after IEP enrollment.
Real-world scenario: A retired Marine gunnery sergeant turns 65 in August. He files with SSA in May (3 months before).
Both Part A and Part B become effective August 1. TRICARE Select terminates July 31, and TFL activates August 1 — zero gap. WPS begins paying secondary on his first civilian claim in September.
What should I do?
- 1Mark your enrollment window on your calendar — start 4 months before your 65th birthday.
- 2File for both Part A and Part B with Social Security at ssa.gov/medicare or 1-800-772-1213.
- 3Aim to enroll in the FIRST three months of your IEP so coverage starts the first of your birthday month.
- 4Within 30 days of your Medicare effective date, log into milConnect and verify Part A and Part B dates are reflected in DEERS.
- 5Contact Social Security with any questions about timing — they administer Medicare enrollment, not Medicare itself.
Questions people commonly ask
- I'm turning 65. What should I do first?
- When exactly does my coverage start?
- Do I need to enroll if I'm already on Social Security?
- Does my spouse have her own IEP?
Continue learning
— suggested by the knowledge graph- What is Medicare? A complete overview for retired militaryA plain-English, handbook-grounded overview of the federal health insurance program for people 65 and older, written specifically for retired service members and their families.
- Understanding Original Medicare (Parts A & B) for veteransExactly what Part A and Part B cover, what they cost in 2026, and why both are required to keep TRICARE For Life.
- Creditable CoverageNon-Medicare coverage that CMS deems at least as good as a standard Medicare Part D plan — TRICARE Pharmacy qualifies, so TFL beneficiaries don't need Part D.
- Creditable Drug CoveragePrescription drug coverage that CMS certifies is at least as good as standard Medicare Part D — including TRICARE Pharmacy and VA Pharmacy.
- Disability Medicare Eligibility (Under 65)Medicare eligibility before age 65 — automatic after 24 months of SSDI, immediately for ALS, and based on dialysis/transplant for ESRD.
- IRMAA (Income-Related Monthly Adjustment Amount)An income-based surcharge added to your Medicare Part B and Part D premiums when your modified adjusted gross income exceeds CMS thresholds.
- Late Enrollment Penalty (Part B and Part D)A permanent monthly surcharge added to your Part B (10% per 12 months delayed) or Part D (1% per month delayed) premium for as long as you have Medicare.
- Medicare Part D and TFLWhy TFL beneficiaries do not need (and usually should not enroll in) a standalone Medicare Part D plan.
- What is the Initial Enrollment Period (IEP)?The 7-month window around your 65th birthday — 3 months before, your birthday month, and 3 months after — when you first enroll in Medicare without penalty.
- What is the General Enrollment Period?January 1 – March 31 each year. It's the backup enrollment window for people who missed their IEP and don't qualify for a Special Enrollment Period.
- How long does Medicare enrollment take to process?Most online applications are approved in 1–3 weeks. SSA mails the Medicare card within about 30 days of approval.
- I'm turning 65. What should I do first?About 3 months before your 65th birthday, sign up for Medicare Parts A and B at SSA.gov. TRICARE For Life activates automatically once both are effective and DEERS is current.
- How far in advance of 65 should I enroll in Medicare?Apply about 3 months before your birthday month so coverage starts the first day of that month and TFL begins without a gap.
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Last reviewed January 2026 against the 2026 Medicare & You and TRICARE For Life handbooks.