What Happens If I Miss the December 7 Deadline?

If you missed December 7, your Medicare coverage does not stop. Nothing gets canceled, nobody drops you, and you are not uninsured on January 1. What happens instead is simpler and less dramatic: whatever you have now rolls into next year with next year’s costs and next year’s rules attached, and the plan you wanted to switch to has to wait.

That’s the whole penalty for most people — a year in a plan you’d rather have changed. It’s a real cost, but it isn’t the emergency the mailers make it sound like. And for a good number of people, December 7 wasn’t actually the last door. There are several others, and which ones apply to you depends entirely on your situation rather than on how sorry you are that you missed the date.

First, what December 7 actually was

Fall Open Enrollment runs October 15 through December 7. Changes you make during it take effect January 1 — as long as the plan receives your enrollment request by December 7. That word matters. It’s a receipt deadline, not a postmark deadline. If you mailed a paper enrollment form on December 5 and it landed on the plan’s desk December 9, you missed the window even though you filled it out in time.

During that window you could have switched Medicare Advantage plans, moved between Original Medicare and Medicare Advantage in either direction, or joined, dropped, or switched a standalone drug plan. Missing it means you can’t do those things at will anymore. It doesn’t mean you can’t do any of them.

If you’re already in a Medicare Advantage plan, you get a second window

This is the one most people don’t know about. Medicare Advantage Open Enrollment runs January 1 through March 31, and it’s available to anyone who’s enrolled in a Medicare Advantage plan at the start of the year. During it you can:

• Switch to a different Medicare Advantage plan, with or without drug coverage
• Drop your Medicare Advantage plan and return to Original Medicare — and if you do, you can also join a standalone Medicare drug plan

Coverage starts the first of the month after the plan gets your request. So a switch made in January starts February 1, and you’d spend January in your old plan.

Two limits keep this from being a full second chance at Open Enrollment. You only get one change. Not one per month — one, total, for the whole window. And it only works in one direction: if you’re in Original Medicare on January 1, you can’t use this period to move into a Medicare Advantage plan, and you can’t use it to pick up a standalone drug plan.

That second limit is where the disappointment usually lands. Someone on Original Medicare who meant to sign up for a drug plan during the fall and forgot does not get a January do-over. That’s the situation where missing December 7 costs real money, and it’s covered further down.

The window that shares dates but does something completely different

The General Enrollment Period also runs January 1 through March 31, and the overlapping dates cause endless confusion. These are two different windows doing two different jobs.

The General Enrollment Period is for people who don’t have Part A and Part B yet and need to sign up. Coverage starts the month after you sign up. If that’s you — you turned 65, you didn’t enroll, and you don’t qualify for a Special Enrollment Period — this is your path in, and it has nothing to do with December 7.

Medicare Advantage Open Enrollment is for people who already have Medicare and want to change how they get it. One period gets you into Medicare; the other moves you around inside it.

Special Enrollment Periods don’t care about December 7

If a qualifying life event happens to you, a window opens on its own schedule. The fall deadline is irrelevant to these. The common ones:

Two of these deserve emphasis. If you have Medicaid or Extra Help, you get a monthly chance to change drug coverage, with the change effective the first day of the following month — December 7 was never really your deadline in the first place. And the 5-star Special Enrollment Period opens December 8, the day after the deadline you just missed. If a 5-star plan serves your area, you have most of the following year to use that window once.

When missing the deadline actually costs money

For someone switching between plans, the cost of missing December 7 is inconvenience. For someone who was supposed to start coverage, it’s a recurring bill.

Drug coverage. If you go 63 days or more in a row without Medicare drug coverage or other creditable drug coverage after your Initial Enrollment Period ends, you may owe a Part D late enrollment penalty. It’s 1% of the national base beneficiary premium ($38.99 in 2026) for every full month you went without, rounded to the nearest $0.10 and added to your monthly premium. Medicare’s own example: 14 uncovered months is a 14% penalty, which works out to $5.50 a month in 2026. It isn’t a one-time fee. You generally pay it for as long as you have Medicare drug coverage, even if you switch plans later. If you qualify for Extra Help, you don’t pay it at all.

Part B. If you needed to enroll in Part B and didn’t, you’ll pay an extra 10% for each full year you could have signed up but didn’t. Medicare’s example: waiting two full years means a 20% penalty added to the standard premium ($202.90 in 2026), for a monthly total of $243.50. Like the drug penalty, it’s added to your premium rather than charged once, and for most people it lasts as long as they have Part B.

Both penalties are why “I’ll deal with it next fall” is the expensive answer if you’re missing coverage rather than just wanting to change it. If you have no drug coverage right now, the clock is running today.

What people get wrong about the aftermath

Thinking coverage lapses. It doesn’t. Your current plan renews unless it told you otherwise. If you got a Plan Non-Renewal Notice in October saying your plan is leaving, that’s a different situation with its own window running December 8 through the end of February.

Thinking January 1 through March 31 is a redo of the fall. It’s one change, only for people already in a Medicare Advantage plan, and it can’t be used to add a standalone drug plan if you’re in Original Medicare.

Assuming Medigap has the same deadline. Medigap doesn’t run on the fall calendar at all — you can apply any time of year. The catch is different: outside your one-time six-month Medigap Open Enrollment Period, and without a guaranteed issue right, there’s no federal guarantee a company will sell you a policy, and health history can raise the price or get you turned down.

Waiting instead of asking. Special Enrollment Periods are granted case-by-case for some situations, including being given misleading information by a plan representative. If something unusual kept you from enrolling, that’s worth a phone call rather than an assumption.

What to do now

Check whether any Special Enrollment Period applies to you — moving, losing coverage, Medicaid, Extra Help, a plan leaving. If you’re in a Medicare Advantage plan, mark January 1 through March 31 and use your one change deliberately rather than reflexively. If you have no drug coverage at all, treat that as the item to solve first, because it’s the one accumulating cost.

Free, unbiased help exists for exactly this. Your State Health Insurance Assistance Program (SHIP) offers one-on-one counseling and isn’t connected to any insurance company. 1-800-MEDICARE (1-800-633-4227) is available 24 hours a day, 7 days a week; TTY users can call 1-877-486-2048.

Missing a deadline feels like a door slamming. In Medicare, it’s usually just a slower door.

Sources: Medicare.gov, “Open Enrollment” (medicare.gov/health-drug-plans/open-enrollment); Medicare.gov, “Joining a plan” (medicare.gov/basics/get-started-with-medicare/get-more-coverage/joining-a-plan); Medicare.gov, “Special Enrollment Periods” (medicare.gov/basics/get-started-with-medicare/get-more-coverage/joining-a-plan/special-enrollment-periods); Medicare.gov, “When does Medicare coverage start?” (medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start); Medicare.gov, “Avoid late enrollment penalties” (medicare.gov/basics/costs/medicare-costs/avoid-penalties); Medicare.gov, “How much does Medicare drug coverage cost?” (medicare.gov/health-drug-plans/part-d/basics/costs); Medicare.gov, “When can I buy a Medigap policy?” (medicare.gov/health-drug-plans/medigap/ready-to-buy/when).