Medicare Open Enrollment: the Window, and the Penalties That Never Stop

Most missed deadlines cost you once. Medicare has two that charge you every month for the rest of your life, and a window that opens on 15 October and closes on 7 December.

If you are helping a parent with this, the useful thing you can do is not advice — it is putting three dates in a diary before the post starts arriving.

When is the window?

October 15 to December 7, every year. Medicare.gov's description of what you can do in it is broad: "join, drop, or switch to another Medicare Advantage Plan with or without drug coverage," switch "from Original Medicare to a Medicare Advantage Plan or from a Medicare Advantage Plan to Original Medicare," and "join, drop, or switch to another Medicare drug plan if you're in Original Medicare."

Whatever you choose takes effect "January 1 of the next year" — and the qualifier is the part to note: "the plan must get your enrollment request by December 7." Not postmarked by, not started by. Received by.

The practical consequence is that 7 December is a hard stop, not a target. Anyone intending to deal with it "in the first week of December" has left themselves almost no margin for a plan's processing, a website problem, or a question that needs answering first.

What happens if you miss it?

You keep what you have until the following January. Plans change their costs, their drug formularies and their networks every year, so "keeping what you have" is not the same as nothing changing — it means absorbing next year's version of your current plan without having looked at the alternatives.

For most people that is expensive rather than catastrophic. The genuinely serious consequences sit elsewhere, in the late enrollment penalties.

Why are the late penalties permanent?

Because they are surcharges on your premium rather than one-off fines, and medicare.gov is unambiguous about how long they last.

For drug coverage: "you'll pay an extra 1% for each month (that's 12% a year)" if you go "63 days or more without creditable drug coverage." The penalty is based on the national base beneficiary premium, which is set annually — and critically, "this monthly penalty is added for as long as you have Medicare drug coverage, even if you switch plans."

For Part B it is steeper still: "you'll pay an extra 10% for each year you could have signed up for Part B, but didn't," and that also continues indefinitely.

Sit with the arithmetic for a moment. Someone who goes two years without creditable drug coverage carries roughly a 24% surcharge — not for two years, but for every month they hold drug coverage thereafter. A decision made once, or more often not made at all, becomes a line on every statement for the rest of their life.

The 63-day figure is worth writing down separately. It is the gap that triggers the penalty, and it is short enough to be crossed by a lapsed employer plan nobody noticed had ended.

What is the January window, then?

A narrower one that gets confused with the main event. The Medicare Advantage Open Enrollment Period runs January 1 to March 31, and it only helps people already in a Medicare Advantage plan: you can "switch to another Medicare Advantage Plan," or "drop your Medicare Advantage Plan and return to Original Medicare" and join a separate drug plan.

Changes made then take effect "the first of the month after the plan gets your request" rather than on a fixed date.

What it is not is a second chance for everyone. If you are in Original Medicare in January, this window does not let you switch drug plans. Treating it as a fallback for a missed December deadline is how people discover the difference at the point it matters.

Which reminders are worth setting?

Three, annually, and the first two do the work:

• 1 October. Two weeks before the window opens. This is when the Annual Notice of Change from the current plan should have arrived, setting out what is changing for next year. Reading it is the whole task, and it is the step most often skipped.
• 10 November. Roughly halfway. Enough time to compare plans properly and still have four weeks of margin.
• 1 December. The last comfortable moment, given the request must be received by the 7th.

If you are doing this with a parent, set them on your own phone as well as theirs. In ReminderIt you can set a recurring annual reminder by message — "remind me every year on 1 October to check Mum's Medicare plan notice" — and it reads the schedule back before saving. Reminders going to someone else's number need their agreement: the system places a consent call first.

What this page is not

Advice about which plan to choose. That depends on prescriptions, doctors, travel, budget and health in ways no article can weigh, and getting it wrong has real costs.

Free, unbiased help exists and is underused: 1-800-MEDICARE, and the State Health Insurance Assistance Program (SHIP) in each state, which provides counselling at no charge and does not sell anything. That last distinction matters in a season when a great deal of the mail arriving is from people who do.

These are the federal rules as medicare.gov publishes them; specifics change annually, so check the current year's figures before acting. What does not change is the shape: a fixed window, a hard receipt deadline, and two penalties that never stop.

Source: medicare.gov — Joining a plan (Open Enrollment 15 October to 7 December, the 1 January effective date and the 7 December receipt requirement; the 1 January to 31 March Medicare Advantage Open Enrollment Period) and Avoid late enrollment penalties (the 1% per month Part D penalty, the 63-day creditable coverage rule, the 10% per year Part B penalty, and the permanence of both).