The Medicare General Enrollment Period runs from January 1 through March 31 each year. It lets you sign up for Part B or Part A that you pay a premium for if you missed your Initial Enrollment Period and do not qualify for a Special Enrollment Period.

When Does Coverage Start?

You can enroll from January 1 through March 31. Coverage starts the first day of the month after you sign up.

For example, if you enroll in February, coverage generally starts March 1. Signing up earlier can shorten the time you are without coverage.

Will There Be a Penalty?

Possibly. The Part B late-enrollment penalty generally adds 10% of the standard premium for each full 12-month period you could have had Part B but did not. In most cases, you pay it for as long as you have Part B.

If you pay a premium for Part A, you may also owe a Part A late-enrollment penalty. The exact result depends on when you were eligible and whether you had coverage that protected a delay.

What Should You Do Next?

Apply through Social Security and confirm your coverage dates. If you already have Part A and add Part B for the first time, the period to join Medicare Advantage begins three months before the first month you have both parts and ends two months after that month. Medicare lists the enrollment windows.

Ask Medicare to confirm the Part D window that applies to your situation; do not assume it is identical to the Advantage window. If you are 65 or older when Part B starts, investigate your six-month Medigap Open Enrollment Period.

Before using the General Enrollment Period, ask Social Security whether you can sign up through a Special Enrollment Period based on your employment or another qualifying circumstance.

For a February enrollment with a March 1 Part B start, arrange the other coverage around March 1. Keep the Social Security confirmation so a plan or Medigap insurer can verify when Part B began.

Medicare policy sources last checked: October 8, 2026.