Medicare · Enrollment · Deadlines
Medicare enrollment deadlines — every window, in plain language.
Every Medicare enrollment deadline that matters — the Initial Enrollment Period, the General Enrollment Period, and Special Enrollment Periods, plus the late-enrollment penalties for Parts A, B, and D. A clear timeline of when each window opens, what triggers the SEPs, and what happens if you miss the dates. Written to be read straight through or jumped into by section.
Sit next to a parent or a client on the call? mote-financial@polsia.app — or call 229-469-1201.
What you’ll find on this page
- 01The Initial Enrollment Period (IEP).
- 02The General Enrollment Period (GEP).
- 03Special Enrollment Periods (SEPs).
- 04Late-enrollment penalties (A, B, D).
- 05The deadline timeline.
Want it sized up against your specific date? Book a 30-minute consultation — bring your birthday, your employer size, and your prescription list.
Comparing Medigap in Georgia? Read the Georgia Supplement guide.
01 · Your first enrollment window
The Initial Enrollment Period (IEP).
The seven-month window around your 65th birthday — and how the effective date shifts as you sit later in it.
Window shape
Three months before your birth month, the birth month itself, and three months after. Seven months total.
3 months before your birth month
Starts the 1st of your birth month
The earliest effective date — no coverage gap if you enroll here.
During your birth month
Starts the 1st of the following month
A one-month gap is the most common surprise.
1, 2, or 3 months after
Starts the 1st of the month after you enroll
Each month of delay stacks another month without coverage.
Each month of delay after your birth month stacks another month without coverage — not a penalty yet, just no insurance for the underlying months. The penalty comes if you also miss the next enrollment cycle. That’s where Section 04 earns its name.
The birthday-rule exception
If your birthday falls on the 1st of the month, Social Security treats your whole birth month as the previous month. So if you were born on April 1, Medicare treats April as March — your IEP shifts a month earlier, and Part B kicks in March 1 instead of April 1.
People born on the 1st are the most common source of “my Medicare started a month earlier than I expected” calls. Easy to miss until the bill arrives.
02 · The annual fallback
The General Enrollment Period (GEP).
January 1 – March 31 every year. The catch-up window for people who missed their IEP, with the post-2023 effective-date rule and the penalty math it carries.
Triage a missed window →The GEP is the annual fallback. If your IEP has already closed and no Special Enrollment Period applies, January through March is the next chance to enroll in Parts A and B (Parts C and D have a parallel spring window). Post-2023, coverage starts the 1st of the month after you enroll — the old “wait until July 1” rule is gone — but the late-enrollment penalty math is unchanged.
- 01GEP
- 02GEP
- 03GEP
- 04OEP
- 05OEP
- 06OEP
When it runs
January 1 through March 31 every year, for Parts A and B (and for Part D / Medicare Advantage in a parallel spring window). The same three-month block — a fixed annual feature of the Medicare calendar.
What changed in 2023
Coverage now starts the 1st of the month after you enroll — no more waiting until July 1. The gap between signing up and care starting is shorter, but the penalty math still applies if your IEP window has already closed.
Who actually uses it
People who missed their IEP — usually because they were still working past 65 without creditable coverage and didn’t realize the SEP clock, or because they recently moved off creditable employer / marketplace coverage. GEP is the catch-up window, not the preferred one.
Why it costs more
GEP enrollment during a lapse period accrues the Part B late-enrollment penalty (10% per 12 months of delay) for as long as you stay on Part B. The penalty is typically lifetime and rides along on every monthly premium until a SEP or low-income subsidy forgives it.
GEP comes with a tax
If your IEP closed without a SEP, every month of gap counts toward the Part B late-enrollment penalty. A 14-month delay rounds up to a 12-month bucket — a 10% lifetime bump to your Part B premium. The pattern we see: people recover their enrollment, take the penalty, and settle into a plan that fits less well than the one they could have picked at 65. The right move is never to reach GEP deliberately; the right move is to use a SEP if one applies.
03 · Trigger-driven, year-round
Special Enrollment Periods (SEPs).
Life changes — losing employer coverage, moving out of a plan’s service area, Medicaid shifts — each open a SEP with its own window length. Most are short; a few are continuous.
The rule
A SEP is trigger + proof + clock. Identify the trigger first, gather the proof (an employer letter, a lease, a Medicaid notice), and the clock starts from the documented event date.
A SEP is what saves you from the GEP-and-penalty math when a life event takes your existing coverage away. The most common triggers below — we see the first two on almost every call with a retiree or a spouse-of-retiree.
Loss of employer group coverage (active employment)
Part B SEP — 8 months
From the end of active employment or active group coverage (whichever comes first), as long as you were continuously creditable. COBRA is not active employment and does not extend this clock — don’t wait out COBRA before enrolling.
Loss of creditable drug coverage
Part D SEP — 63 days
From the end of creditable prescription coverage (employer group plan, VA, TRICARE, marketplace). A “creditable coverage” letter from the employer or plan each year is the proof — keep them.
Move out of plan service area
SEP starts the month before + ends 2 months after the move
For Medicare Advantage and Part D plans (Original Medicare has no service area). A documented address change (driver’s license, voter registration, USPS) is the trigger document. Some moves are considered “permanent” automatically; non-permanent stays rarely qualify.
Change in Medicaid / Extra Help eligibility
Quarterly SEP while dual-eligible
People on both Medicare and Medicaid, or approved for the Part D Low-Income Subsidy (Extra Help), get a quarterly chance to switch Advantage or Part D plans outside the fall OEP — useful when plan formularies stop matching the active drug list.
Institutional care (skilled nursing or long-term)
Continuous while institutionalized + 2 months after discharge
Beneficiaries moving into or out of a skilled nursing facility, long-term care hospital, or psychiatric facility get a continuous SEP for Advantage and Part D — because prior authorization rules and formularies differ from the home-care mix.
Federal employee error (Medicare was supposed to enroll you)
Equitable relief SEP — varies
If a federal employee (SSA, CMS, a carrier) made a documented error that kept you from enrolling on time, equitable relief opens a SEP. The proof is the agency letter — call us before assuming it counts as a trigger.
5-star plan available in your county
One-time switch, Dec 8 – Nov 30 (annual)
CMS rates Medicare Advantage and Part D plans on a 1-to-5 scale. A 5-star plan in your area opens a one-time-per-year switch into it. Not a replacement for the regular OEP — best used as a “swap up” once a year.
SEPs and the late-enrollment penalties
A SEP only waives the penalty if your coverage was continuously creditable for the entire gap. The two proof documents to keep: an annual “creditable coverage” letter from the employer or plan (for the Part D penalty), and a record of active employment + active enrollment (for the Part B penalty). Without either, the accrual continues across the gap.
04 · What you pay if you miss them
Late-enrollment penalties (A, B, D).
Three separate penalty formulas, almost all lifetime. Each one accrues during a gap without creditable coverage — even if you didn’t know the gap existed.
The bigger cost
Penalty dollars are taxes. The real cost during the gap is medical: denied Part B claims (20% of the bill at the doctor), denied Part D prescriptions, and denied inpatient days past the 60-day mark. The penalty math is the smaller bill.
Part A penalty (when Part A isn’t premium-free)
+10% of the Part A premium, doubled (×2) the length of the no-coverage period
Applies if you don’t get premium-free Part A (fewer than 40 working quarters) and you don’t enroll when first eligible. The penalty lasts for twice the number of years you went without coverage — so a two-year delay adds a four-year 10% bump. Unlike Part B, this one ends.
Part B late-enrollment penalty
+10% of the Part B premium for every 12 months you could have had Part B and didn’t
Typically lifetime. Only goes away if you later qualify for a Special Enrollment Period or a low-income subsidy (Extra Help / Medicaid). The bigger cost during the gap is medical — claim denials for outpatient care land on you, not the plan.
Part D late-enrollment penalty
+1% of the national base premium for every month without creditable drug coverage
Also typically lifetime. The proof is a “creditable coverage” letter from the employer or plan each year — keep them. SEP for involuntary loss of creditable drug coverage exists, so don’t guess at the trigger; call before the 63-day clock expires.
What counts as “creditable”
For the Part D test: employer group plans (from active employment, not COBRA), ACA marketplace coverage, VA drug coverage, and TRICARE. A “creditable coverage” letter from the employer or plan each year is the proof — keep them. For the Part B test: the same active-employer group coverage, with employer size clearing the 20-employee threshold.
05 · Putting the windows together
The deadline timeline.
A year-strip view of every recurring window, and a by-stage view of the same windows from the beneficiary’s situation. Pick the row that matches your life; the cell that matches your month.
A. Year-strip — what runs when
- 01Jan
GEP opens (1/1). Aging-in IEP active.
GEP
- 02Feb
GEP runs.
GEP
- 03Mar
GEP ends 3/31. Spring OEP for Advantage / Part D.
GEP
- 04Apr
Post-GEP effective dates lock in.
- 05May
Five-star SEP window open year-round.
SEP windows open
- 06Jun
Five-star SEP window open year-round.
SEP windows open
- 07Jul
Five-star SEP window open year-round.
SEP windows open
- 08Aug
Plan Annual Notice of Change arrives.
- 09Sep
Pre-OEP reviews; carrier outreach begins.
- 10Oct
Annual OEP opens 10/15 — review your drug list.
Annual OEP
- 11Nov
Annual OEP runs; ends 12/7.
Annual OEP
- 12Dec
New plan-year coverage starts 1/1 of the next year.
B. By beneficiary stage — which window applies to you
Aging in at 65
IEP — single best window
The 7 months around your 65th birthday
If you’re aging in cleanly with no active employer coverage, the IEP is the cleanest pass through Medicare you’ll ever get. Enroll in the first three months of the window and coverage starts the 1st of your birth month.
Working past 65 with creditable employer coverage
Defer Part B; Part A optional
While active employment + active group coverage continues
If your employer has 20+ employees, the active group plan is primary. You can defer Part B without penalty — and skip Part A entirely if you’re still contributing to an HSA (Part A disqualifies HSA contributions retroactively).
Retiring or losing employer coverage
Part B SEP — 8 months
From the end of active employment / active coverage
The 8-month clock starts at the end of active employment or active group coverage (whichever comes first). COBRA is not active coverage and does not extend the clock — enroll in Part B before the 8 months run out.
Missed your IEP, no SEP available
GEP with penalty math
January 1 – March 31 every year
The annual fallback window. Coverage now starts the 1st of the month after you enroll (post-2023), but the Part B penalty continues to accrue at 10% per 12 months of delay for as long as you stay on Part B.
Losing creditable drug coverage
Part D SEP — 63 days
From the end of creditable Rx coverage
Whether from a spouse’s retirement, a job change, or a marketplace plan ending. The 63-day window is short — pick a Part D plan before the clock expires or the late-enrollment penalty starts accruing monthly.
The one-line summary
The IEP is the cleanest pass through Medicare. A SEP avoids the penalty if a life event applies. The GEP is the catch-up with a tax. Outside all three, you’re paying out of pocket and accruing penalties you’ll carry for years. The right move almost always is to nail the IEP date on the calendar before the clock starts.
Next step
Pull your window forward on the calendar.
We walk through your specific dates on a 30-minute, no-cost call — your 7-month IEP window, whether a SEP applies, and how the penalty math lands if you’re already in a gap. Bring the question this page raised — the birthday rule, the 20-employee rule, the COBRA trap, the 63-day drug-coverage clock — and we’ll size it up against your situation, not a generic script.
- · No cost. No obligation. Carrier-paid only after you enroll.
- · Independent — multi-carrier comparison, not a single plan sheet.
- · A real person on the call — and the same person next year.