Medicare 2026

Miss a Medicare Deadline? Here's What It Costs You

ARLINGTON, Va. — Medicare runs on a calendar, and the calendar has teeth. Miss the window to sign up for Part B or Part D, and you can end up paying a penalty every month for as long as you have the coverage. The good news: the deadlines are knowable, and most penalties are avoidable if you understand how the dates line up.

This guide walks through the timing — when your first window opens, what happens if you let it close, and how later windows can help you get back on track.

The Initial Enrollment Period is your first deadline

For most people, Medicare eligibility starts at 65. Your Initial Enrollment Period (IEP) is a 7-month window: the three months before the month you turn 65, your birthday month, and the three months after.

Signing up during this window is the cleanest way to avoid late penalties for both Part B (doctor and outpatient care) and Part D (prescription drugs). If you're already getting Social Security benefits when you turn 65, you'll usually be enrolled in Parts A and B automatically. If you're not, you have to sign up yourself through the Social Security Administration.

Arlington is in Arlington County, where Medicare's national rules apply the same as anywhere else in the country — the deadlines don't shift based on where you live.

What happens if you miss it: Part B

If you don't sign up for Part B during your IEP and you don't qualify for a Special Enrollment Period, you'll generally have to wait for the General Enrollment Period, which runs January 1 through March 31 each year. Coverage then begins the month after you enroll.

The penalty: your monthly Part B premium goes up by 10% for each full 12-month period you could have had Part B but didn't. That surcharge sticks with you for as long as you have Part B — not just a year or two.

Example: if you waited three full years past your IEP without a qualifying reason, your Part B premium would be 30% higher, every month, essentially for life.

What happens if you miss it: Part D

Part D has its own clock. If you go 63 or more days in a row after your IEP without "creditable" prescription drug coverage — coverage at least as good as basic Medicare drug coverage — you can be charged a late enrollment penalty when you finally sign up.

The math: 1% of the "national base beneficiary premium" for every full month you went without creditable coverage, rounded to the nearest 10 cents, added to your monthly Part D premium. Because the base premium can change each year, the dollar amount of your penalty can drift over time.

You can only sign up for Part D (or a Medicare Advantage plan with drug coverage) at certain times: during your IEP, during the Annual Enrollment Period from October 15 to December 7, or if you qualify for a Special Enrollment Period.

How the enrollment windows interact

It helps to see the calendar as a set of overlapping doors:

• Initial Enrollment Period — your 7-month window around age 65. Best time to avoid penalties.
• General Enrollment Period (Jan. 1 – March 31) — the fallback for Part B if you missed your IEP.
• Annual Enrollment Period (Oct. 15 – Dec. 7) — when most people can join, switch or drop Part D and Medicare Advantage plans for the coming year.
• Medicare Advantage Open Enrollment (Jan. 1 – March 31) — a chance for people already in a Medicare Advantage plan to switch once or return to Original Medicare.
• Special Enrollment Periods — triggered by specific life events, such as losing job-based coverage or moving.

If you delay Part B because you had employer coverage from active work (yours or a spouse's), you generally get an 8-month Special Enrollment Period after that job or coverage ends to sign up without a penalty. Retiree coverage and COBRA usually do not count as active employer coverage for this rule — a common and costly misunderstanding.

How to avoid the penalty in the first place

A few practical habits go a long way:

• Mark your IEP on the calendar as soon as you know your Medicare start date. Set a reminder three months before you turn 65.
• Check whether any drug coverage you have is "creditable." Employers and insurers are required to send a notice each year. Keep those notices — they're your proof.
• Don't assume you're auto-enrolled. If you're not drawing Social Security yet, you have to actively sign up.
• If you're still working past 65, talk to your benefits office about how your plan works with Medicare before you make a decision.
• Contact your local State Health Insurance Assistance Program (SHIP) for free, one-on-one counseling. Virginia's SHIP is called the Virginia Insurance Counseling and Assistance Program (VICAP).