Medicare 101
Medicare Enrollment Periods
Medicare runs on enrollment windows, and using the right one is how you avoid penalties and lock in the plan you want. The big four are the Initial Enrollment Period (IEP) around your 65th birthday, the Annual Enrollment Period (AEP) every fall, the Medicare Advantage Open Enrollment Period (MA-OEP) in the new year, and Special Enrollment Periods (SEPs) triggered by life events. Here's what each one actually lets you do.
Initial Enrollment Period (IEP)
Your IEP is a 7-month window: the 3 months before your 65th-birthday month, your birthday month, and the 3 months after. This is when you first sign up for Parts A and B and choose a plan. Enroll in the first three months and coverage starts the month you turn 65; wait until later in the window and it can start later. This is the cleanest time to enroll.
Annual Enrollment Period (AEP): Oct 15 – Dec 7
Every fall, from October 15 to December 7, anyone on Medicare can change plans for the next year — switch Medicare Advantage plans, change Part D drug plans, or move between Original Medicare and Advantage. Changes take effect January 1. We review every client's plan during AEP because carriers change premiums, drug formularies, and networks every single year.
Medicare Advantage Open Enrollment (MA-OEP): Jan 1 – Mar 31
If you're already in a Medicare Advantage plan on January 1, you get one more chance from January 1 to March 31 to switch to a different Advantage plan or drop back to Original Medicare (with a Part D plan). It's a one-change window — useful if the plan you picked isn't working out.
Special Enrollment Periods (SEPs)
Life events open SEPs: losing employer coverage, moving out of your plan's service area (say, relocating from Grand Junction to Moab), qualifying for Medicaid or Extra Help, or your plan leaving the market. Each SEP has its own timing — usually about two months — and its own rules. We identify which SEP you qualify for and act inside the window.
Miss a window and the penalties are permanent
Skipping Part B at 65 without creditable coverage adds 10% to your premium for every 12 months you could have had it — for life. The Part D penalty is about 1% of the national base premium per month you go without creditable drug coverage — also for life. We track your dates so a missed deadline never costs you.
The General Enrollment Period (the safety net)
If you miss your Initial Enrollment Period and don't qualify for a Special Enrollment Period, the General Enrollment Period runs January 1–March 31 each year. You can sign up for Part B then, with coverage starting the first of the month after you enroll — but you may owe the late-enrollment penalty. It's a safety net, not a substitute for enrolling on time, which is why we plan your timing carefully.
How each period fits together
Think of it as a sequence: your IEP is your one-time on-ramp at 65; SEPs cover life events in between; AEP is the annual checkup every fall; MA-OEP is a short do-over in the new year; and the General Enrollment Period is the last resort if you missed everything. Knowing which window you're in — and what it actually lets you change — is half of using Medicare well. We keep a personal calendar for every client so nothing slips.
Common SEPs on the Western Slope
The Special Enrollment Periods we use most for local clients: moving between counties or into Utah (a move from Grand Junction to Moab changes your plan options); losing employer or retiree coverage; gaining or losing Medicaid or Extra Help; and your plan being discontinued for the next year. Each has its own clock, usually about two months, and its own rules — so the moment your situation changes, let us know and we'll act inside the window.
Local Medicare help across the Western Slope
Medicare rules are federal, but the plans, provider networks, and prices are local — and they change every year. Medicare On Main is an independent agency based in Grand Junction, Colorado (Mesa County), serving Grand Junction, Fruita, and Palisade plus Moab (Grand County) and Monticello (San Juan County), Utah — and Brian Penner is licensed in 18 states. We compare the plans we offer in your county against your own doctors, prescriptions, and budget, confirm your local providers are in-network, and stay your advisor for claims, appeals, and the annual review — at no cost to you, because carriers pay licensed agents, not you. That local, year-round help is the difference between reading about Medicare and having a plan built around your life.
Questions, answered
When is Medicare's Annual Enrollment Period?
October 15 to December 7 each year. Changes you make take effect January 1. We review your plan every fall to make sure it's still your best fit before the window closes.
What's the difference between AEP and the Medicare Advantage Open Enrollment Period?
AEP (Oct 15–Dec 7) is open to everyone and allows any plan change for next year. MA-OEP (Jan 1–Mar 31) is only for people already in a Medicare Advantage plan and allows one switch.
I'm moving to a new county — can I change plans?
Yes. Moving out of your plan's service area triggers a Special Enrollment Period. If you're relocating anywhere across the Western Slope or into Utah, let us know and we'll handle the switch inside your window.
What happens if I miss my Initial Enrollment Period?
You may have to wait for the General Enrollment Period and could face lifelong Part B and Part D penalties. If you had creditable employer coverage, a Special Enrollment Period may protect you — we'll confirm which applies.
Official Medicare sources
We point you to the federal sources so you can verify everything. For current-year figures and to compare the plans available in your area:
- Medicare.gov — the official U.S. government site for Medicare costs, coverage, and rules.
- Medicare Plan Compare — the official tool to compare Medicare Advantage and Part D plans by ZIP.
- Social Security (ssa.gov) — enroll in Medicare Parts A & B and check your eligibility.
- CMS.gov — Centers for Medicare & Medicaid Services, which runs the program.
Education and estimates only — confirm current figures on Medicare.gov before enrolling. We do not offer every plan available in your area.
Talk to a local Medicare advisor
Free, no pressure — we compare your options for you.
Last updated . Maintained by the Medicare On Main Data Desk · reviewed by Brian Penner, Independent Medicare advisor (NPN 16493717).