Enrollment periods
The Medicare enrollment windows, and which one you are in
Figures on this page checked . Medicare and marketplace numbers reset every year — if you are reading this long after that date, call and we will tell you what moved.
Start here: which window applies to you
Almost everyone lands in one of these five situations. Find yours, then read that section.
- Turning 65 and not working: your Initial Enrollment Period. Seven months around your birthday.
- Turning 65 and still working, with employer coverage: you may be able to wait. The eight-month Special Enrollment Period is what protects you, and it starts sooner than people expect.
- Already on Medicare, want to change plans for next year: Annual Enrollment, October 15 through December 7.
- Already on a Medicare Advantage plan and it is not working out: Advantage Open Enrollment, January 1 through March 31. One change.
- Missed a window and have no coverage: the General Enrollment Period, and probably a penalty. Read that section last, and then call us.
A sixth group exists and gets left out of every chart: people whose circumstances qualify them for a Special Enrollment Period that has nothing to do with employment. Those are at the bottom of this page.
Initial Enrollment Period: seven months, and the half you want
Your Initial Enrollment Period is 7 months long: the three months before your birthday month, the birthday month itself, and the three months after. Turn 65 in October and it opened in July and closes at the end of January.
Which month you pick inside that window changes when coverage starts, and the two halves behave differently.
- Sign up in the first three months: coverage begins the first month you are eligible, which is the month you turn 65.
- Sign up in your birthday month or later: coverage begins the month after you enroll.
So enrolling in the last month of your window means coverage starts a month after that. If a retirement date, a COBRA end date, or a surgery is sitting in the middle of that gap, you pay for it. Enroll early in the window. It costs nothing to do it in July instead of January.
This rule changed in 2023
Before January 1, 2023, a late-window enrollment could delay coverage by up to three months. Congress removed that. Pages describing the old delay are still all over the internet, and some of them belong to companies that should know better.
The longer version, with the October-birthday example worked through, is in our article on the seven-month window.
Still working at 65: the eight-month window, and when the clock starts
If you have group health coverage through your own or your spouse’s current job, you can usually delay Part B without a penalty and pick it up later. The window that lets you do that runs 8 months.
The part that costs people money
Those eight months start when your employment ends or when the group plan ends, whichever happens first. Not when COBRA runs out. Not when retiree coverage ends. COBRA and retiree plans are not current employment, and they do not hold this window open.
People discover this in month eleven of an eighteen-month COBRA election, three months after the window they did not know about closed. At that point the next opportunity is the General Enrollment Period, and the penalty is permanent.
One more condition decides the rest: the size of the employer. Twenty or more employees and the group plan generally pays first, which is what makes delaying safe. Under twenty and Medicare generally becomes primary at 65 whether or not you enrolled, so skipping Part B can leave you holding most of a bill. Multi-employer plans have their own exceptions, and eligibility through disability follows a different rule again.
Tell us your employer size and your last day. That combination takes about four minutes to settle on a phone call and cannot be settled by a web page. The forms and the sequence are here.
Annual Enrollment: October 15 through December 7
This is the yearly window for changing Medicare Advantage and Part D plans. Whatever you choose takes effect on January 1. If you do nothing, you stay where you are.
What you can do inside it:
- Join, switch, or drop a Medicare Advantage plan
- Join, switch, or drop a Part D drug plan
- Return to Original Medicare from an Advantage plan
What it does not do is give you a Medigap policy. Medicare Supplement has no annual window at all — carriers can ask health questions outside your one-time open enrollment, and in most cases they will. That difference catches people every autumn.
In plain terms
“Your plan is changing” is the letter that matters. Every Advantage and Part D plan mails an Annual Notice of Change each September, and the drug list is the part people skip. A medication moving to a different tier can cost more than the premium difference between two plans.
Call us in September rather than in December. The first week of December is the busiest week of our year, and rushing this decision is how people end up in a plan their oncologist does not take.
Advantage Open Enrollment: January 1 through March 31
This one is narrower than it sounds, and it is the window people most often think they have when they do not.
- You have to already be enrolled in a Medicare Advantage plan on January 1.
- You get one change: a different Advantage plan, or back to Original Medicare with a Part D plan.
- Coverage starts the first of the month after the plan gets your request.
If you are on Original Medicare on January 1, this window is not available to you. You cannot use it to join an Advantage plan for the first time, and you cannot use it to pick up a Part D plan on its own.
Leaving Advantage for Original Medicare in this window also raises the Medigap question, and the answer is often no. Outside your one-time Medigap open enrollment, a carrier can decline you for health reasons. Ask before you drop the Advantage plan, not after.
General Enrollment: January 1 through March 31
This is the catch-up window for people who missed their Initial Enrollment Period and had no employer coverage protecting them. Coverage begins the first day of the month after you enroll.
That start rule also changed on January 1, 2023. It used to be that everyone who enrolled in this window waited until July 1, no matter which month they signed up. Sources still describing a July start date are out of date.
What the delay costs
Late Part B enrollment adds 10% of the standard premium for each full 12 months you could have had it and did not. The increase is permanent — it stays on your premium for as long as you have Part B, and it goes up when the standard premium does.
Part D has its own late penalty, calculated separately and also permanent. Going without drug coverage because you take no medications today is one of the more common expensive decisions we see.
If you are reading this because you already missed a window: call. Sometimes there is a Special Enrollment Period available that removes the penalty entirely, and sometimes there is not. Finding out is free and takes one conversation.
The special windows almost nobody is told about
Since 2023 there have been Special Enrollment Periods for specific circumstances beyond employer coverage. They are written into federal regulation, they are not widely publicized, and each one gives you a window to enroll without the late penalty.
- A declared disaster or emergency where you live, if it kept you from enrolling on time
- Bad information from an employer or health plan that led you to miss a window
- Release from incarceration
- Losing Medicaid coverage
- Other exceptional circumstances, decided case by case
We are not the ones who decide whether you qualify. Social Security makes that determination, so raise these with them directly on 1-800-772-1213 even if an agent has told you no. What we can do is tell you which category your situation looks like and what to have ready for the call.
Questions about enrollment windows
How do I know which enrollment period I am in?
If you are approaching 65 and not covered by a current employer’s plan, you are in your Initial Enrollment Period — three months before your birthday month through three months after.
If you are already on Medicare and want to change an Advantage or Part D plan, you are waiting for Annual Enrollment from October 15 to December 7. If you are leaving a job, you are in an eight-month Special Enrollment Period that started the day the job or the plan ended, whichever came first.
If none of those describe you, call us and we will work out which window you are in. That is a five-minute conversation and there is no charge for it.
What happens if I miss my window?
For Part B, you generally wait for the General Enrollment Period from January 1 to March 31, and coverage starts the first of the month after you enroll. The late enrollment penalty adds 10% of the standard premium for every full 12 months you could have had Part B and didn’t, and it stays on your premium permanently.
Before you accept that, check whether a Special Enrollment Period applies. Employer coverage, a declared disaster, being given wrong information by a plan or an employer, leaving incarceration, or losing Medicaid can each open one. Several of these were added in 2023 and are not widely known.
Can I switch to a Medigap plan during Annual Enrollment?
No, and this is the misunderstanding we correct most often in the autumn. Annual Enrollment covers Medicare Advantage and Part D. Medicare Supplement works on a different clock entirely.
Your Medigap open enrollment is six months long and starts when you are both 65 and enrolled in Part B. Inside it, carriers cannot ask health questions or charge you more for your history. Outside it, they generally can, and in Colorado there is no annual birthday rule that reopens the door — a rule several other states have and we do not.
I am still working at 65. Do I need to do anything?
Most people take Part A, because it usually costs them nothing, and delay Part B while they have coverage through current employment at an employer with twenty or more employees.
Two conditions change that answer. If the employer has fewer than twenty employees, Medicare generally becomes primary at 65 and delaying Part B can leave you paying most of your own claims. And if you contribute to a health savings account, enrolling in any part of Medicare stops those contributions, with a tax consequence for the months before you enroll.
Tell us your employer size before you decide either way.
CMS-required disclaimer
We do not offer every plan available in your area. Currently we represent 7 organizations which offer 45 products in your area. Please contact Medicare.gov, 1-800-MEDICARE, or your local State Health Insurance Program to get information on all of your options.