As you learn more about Medicare and your options, you’ll often hear about various enrollment periods. And it can feel like a confusing maze of time frames and rules. Which are the important enrollment periods, and how do you keep them all straight?

It’s critical that you know Medicare’s enrollment time frames. If you miss certain dates, you may lose out on getting the right Medicare plan or coverage for your needs — or get hit with penalties for signing up late.

For example, if you missed your enrollment deadlines for Part B, you may have to pay a 10% penalty on your premium for every 12-month period during which you didn’t have that coverage. And the kicker? You’ll likely have to pay that penalty for as long as you have Medicare.

“It is always a good idea to know the enrollment periods, especially the ones you still may need to use,” says David Armes, principal of Dover Healthcare Planning LLC, a fee-only Medicare adviser in Long Beach, California.

Losing track of these dates can cost you, so we’ve put together a handy chart of the key enrollment periods you may need to know.

*Some people can sign up for Medicare before they turn 65 due to disability or end-stage renal disease. In these cases, the Initial Enrollment Period start date differs, although what you can do during this period stays the same.