If you are approaching 65, the hardest part of Medicare is not choosing a plan. It is knowing exactly when to act. Miss a window and you can face a premium penalty that follows you for the rest of your life, or a gap in coverage that no amount of paperwork will undo.
Here is the timeline, in plain English.
Your Initial Enrollment Period is seven months long
Your Initial Enrollment Period (IEP) opens three months before the month you turn 65, includes your birthday month, and closes three months after it. That is seven months in total, and it is the single most important window in the whole process.
| When | What it means |
|---|---|
| 3 months before your birthday month | The best time to enroll. Coverage starts the first day of your birthday month. |
| Your birthday month | Still fine, but coverage start is delayed by a month. |
| 1 to 3 months after | Allowed, but coverage is delayed further. Avoid if you can. |
If your birthday falls on the first of the month, your window shifts one month earlier. It is a small quirk that catches people out every year.
What happens if you miss it
Missing your IEP without a valid reason means waiting for the General Enrollment Period, which runs 1 January to 31 March each year. Coverage then begins the first day of the month after you sign up.
The bigger cost is the penalty:
- Part B: your premium increases by 10% for each full 12-month period you could have had Part B but did not. This penalty is permanent.
- Part D: a smaller penalty calculated per month without creditable drug coverage, also added to your premium for as long as you have Part D.
These penalties are not a one-off fee. They are added to your monthly premium for life, which is why the seven-month window matters so much.
If you are still working at 65
Working past 65 with employer coverage changes things. If your employer has 20 or more employees and you are covered by that active group plan, you can usually delay Part B without penalty and enrol later through a Special Enrollment Period.
That Special Enrollment Period gives you eight months for Part B, starting when the employment or the group coverage ends, whichever comes first. Part D has a much shorter window, so do not treat them as the same deadline.
Two important cautions:
- If your employer has fewer than 20 employees, Medicare usually becomes your primary payer at 65. Delaying can leave you badly exposed.
- COBRA and retiree coverage do not count as active employer coverage for this purpose. This is one of the most common and most expensive misunderstandings we see.
If you are in this situation, our Turning 65 guidance walks through it in more detail.
The deadline most people regret missing
Separate from everything above, there is a six-month Medigap Open Enrollment Period. It starts the month you are both 65 and enrolled in Part B.
During those six months you have a guaranteed right to buy any Medicare Supplement policy sold in your state, at the standard price, regardless of your health history. Once it closes, insurers in most states can review your medical history, charge you more, or decline you outright.
You cannot get this window back. If a Supplement plan is likely to suit you, this is the moment to act.
Choosing what sits alongside Parts A and B
Original Medicare leaves gaps. There is no annual out-of-pocket cap, and no routine drug coverage. Broadly, you have two routes:
- Medicare Advantage bundles your coverage into one plan, often with drug coverage and extras included, in exchange for using a network and following plan rules.
- Medicare Supplement plus a Part D plan keeps Original Medicare and fills the gaps, usually with wider provider freedom and a higher monthly premium.
Neither is universally better. The right answer depends on your prescriptions, your doctors, how much you travel, and how much predictability you want in a bad year.
If money is tight, check these first
Before you assume a plan is unaffordable, it is worth checking whether you qualify for help. The Medicare Savings Programs can cover premiums and some cost sharing, and the Low Income Subsidy reduces prescription drug costs substantially. Many people who qualify never apply, simply because nobody told them to look.
A simple checklist
- Mark the month three months before your 65th birthday. That is when to start.
- Confirm whether your current coverage lets you delay Part B safely.
- List your prescriptions and your must-keep doctors before comparing plans.
- Decide on Advantage or Supplement before your six-month Medigap window closes.
- Check whether you qualify for a savings program or subsidy.
Common questions
Do I have to enrol at 65 if I am still working?
Not necessarily. With qualifying active employer coverage from a larger employer you can usually delay Part B penalty-free. Confirm your specific situation before deciding, because the rules turn on employer size.
Is Part A really free?
For most people who have paid Medicare taxes for long enough, Part A has no premium. Part B does have a monthly premium, which is income-adjusted.
Can I switch plans later if I choose wrong?
You can change Medicare Advantage and Part D plans during the Annual Enrollment Period each autumn. Switching to a Medicare Supplement later is different, because outside your guaranteed-issue window insurers can assess your health.
When should I actually start looking?
Around four to six months before you turn 65. That gives you time to compare properly rather than making a decision under deadline pressure.
Getting it right the first time
Medicare rewards planning and punishes delay. The rules are knowable, but they are unforgiving, and the costliest mistakes are almost always timing mistakes rather than plan choices.
All Solution Plus works with people across multiple states to map these dates against their own circumstances, at no cost to them. If you would like a second pair of eyes on your timeline, get in touch and we will walk through it with you.
This article is general information, not personalised advice. Your own eligibility, deadlines and costs depend on your circumstances and your state.
