Glossary
Annual Election Period (AEP)
October 15 – December 7 each year — the main window to join, switch, or drop a Medicare Advantage or Part D plan, with coverage starting January 1.
Also known as: AEP, Medicare Open Enrollment, Fall Open Enrollment, Annual Enrollment Period
Quick answer
The Annual Election Period (often called 'Medicare Open Enrollment' or 'AEP') runs October 15 through December 7 every year. During AEP you can join a Medicare Advantage plan, switch from one MA plan to another, switch from MA back to Original Medicare, join a stand-alone Part D plan, or drop Part D. Any change made during AEP takes effect January 1 of the following year.
Why it matters
Medicare Advantage and Part D plans change every year — premiums, networks, formularies, giveback amounts, and extra benefits all reset. AEP is your once-a-year chance to make sure your plan still fits before the new plan year begins. Skipping the review can leave you locked into a worse plan for 12 months.
Why this matters at age 65
If your 65th birthday falls between October 15 and December 7, AEP and your IEP overlap. You can use either window — but plan effective dates differ. AEP changes ALWAYS start January 1, while IEP enrollments may start earlier. Choose carefully if you need coverage to start before January.
When you'll encounter it
Every fall, October 15 – December 7. Plan Annual Notice of Change (ANOC) letters arrive in late September.
Impact on Medicare
Original Medicare itself does not change during AEP. AEP is for choosing how you receive Medicare (Original vs. MA) and which Part D plan, if any, you have.
Impact on TRICARE For Life
TFL is unaffected. TFL continues year-round regardless of AEP decisions. But if you switch from MA back to Original Medicare during AEP, TFL changes from a copay-supplement role back to its primary secondary-payer role.
Impact on Medicare Advantage
AEP is the primary MA decision window. If you're considering a veteran-focused MA-Only plan (Humana USAA Honor, AARP Patriot, Aetna Eagle), AEP is when most enrollments happen.
Military-specific context
For TFL beneficiaries, MA is optional — Original Medicare + TFL is a complete safety net. Use AEP to evaluate if an MA-Only veteran plan with Part B giveback and dental/vision/hearing is worth it for your situation. Never let a marketing agent rush you.
Common misconceptions
- "AEP is when I enroll in Medicare Parts A and B." — No — that's your IEP (around your 65th birthday) or GEP (Jan 1 – Mar 31). AEP is only for MA and Part D choices.
- "If I miss AEP I can't change anything." — You can still switch MA plans during OEP (Jan 1 – Mar 31) and use a 5-star plan SEP or other qualifying SEPs throughout the year.
Common mistakes to avoid
- Ignoring the ANOC letter mailed by your MA plan in September — that's the document showing next year's changes.
- Letting a sales agent enroll you in an MAPD (with Part D) instead of MA-Only — duplicates TRICARE Pharmacy and may have higher cost.
- Switching plans for one extra benefit without checking whether your doctors stay in network.
Real-world scenario: A retired veteran on Humana USAA Honor receives an ANOC in September showing the Part B giveback is dropping from $125 to $80 next year.
During AEP he compares the Aetna Eagle plan (with a $150 giveback in his ZIP) and switches. New plan effective January 1. Saves $840/year while keeping TFL as secondary.
What should I do?
- 1Open the Annual Notice of Change (ANOC) from your current plan the moment it arrives in September.
- 2Between October 15 and December 7, compare your current plan against current-year veteran-focused MA-Only plans for your ZIP.
- 3If you keep an MA plan, choose MA-Only (no Part D) so TRICARE Pharmacy stays primary.
- 4Confirm any new plan enrollment is reflected in Medicare.gov by mid-December — coverage starts January 1.
Questions people commonly ask
- What's the difference between AEP and OEP?
- When does my AEP enrollment take effect?
- Can I switch back to Original Medicare during AEP?
- Do I have to do anything during AEP if I'm happy with my plan?
Continue learning
— suggested by the knowledge graph- Enrolling in Medicare: timing, methods, and the military-specific rulesWhen and how to sign up for Medicare Parts A and B — and the timing that protects your TRICARE For Life activation.
- Avoiding the Medicare late-enrollment penaltyThe Part B late penalty is permanent — and TRICARE does not waive it. Here's how to make sure you never owe it.
- Five-Star Special Enrollment PeriodA once-per-year SEP that lets you switch into a CMS-rated 5-star Medicare Advantage or Part D plan available in your area.
- Beneficiary CategoryHow DEERS classifies you (active duty, retiree, family member, survivor, etc.) — determines which TRICARE plans and cost shares apply.
- COBRA After 65COBRA is not creditable coverage for Part B — using it past 65 instead of enrolling in Medicare causes lifetime late penalties.
- Coverage DecisionA formal decision by a Medicare Advantage or Part D plan about whether — and how — it will cover a service, item, or prescription.
- 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.
- Can I leave Medicare Advantage and go back to Original Medicare + TFL?Yes, during the Annual Enrollment Period (Oct 15 – Dec 7) or the Medicare Advantage Open Enrollment Period (Jan 1 – Mar 31). TFL is waiting whenever you return.
- Can I keep my current doctor if I enroll in Medicare Advantage?Only if they're in the MA plan's network. Always verify with the plan and the doctor's office before enrolling. Network status can change yearly.
- When can I enroll in or switch Medicare Advantage plans?Annual Enrollment Period (Oct 15 – Dec 7) for next-year coverage. MA Open Enrollment Period (Jan 1 – Mar 31) for one change. Special Enrollment Periods for qualifying life events.
- What is the 5-star Special Enrollment Period?A one-time-per-year chance (Dec 8 – Nov 30) to switch into a 5-star-rated Medicare Advantage or Part D plan in your area, outside the normal enrollment windows.
Related lessons
Related glossary terms
Related Official Resources
Continue learning straight from the source. Every link below goes to an official government or DoD resource.
Last reviewed January 2026 against the 2026 Medicare & You and TRICARE For Life handbooks.