One Missed Deadline. Permanent Consequences.

Most people know Medicare exists. Far fewer realize that signing up late, even by a month or two, can follow you for the rest of your life.

How the window works

When you turn 65, you get a seven-month window to enroll in Medicare Part B: the three months before your birthday month, your birthday month, and the three months after.

Miss it, and you may face a premium penalty of 10% for every 12-month period you were eligible but didn't enroll. Not a one-time fee. A permanent increase, added to your premiums for life. The consequences are wildly out of proportion to the mistake, which is exactly why it deserves a spot on your calendar years in advance.

The exception that confuses everyone

If you're still working at 65 and covered by an employer plan, different rules apply, and you may be able to delay without penalty. The details matter enormously: whether your employer coverage counts as creditable, what happens to a covered spouse, and how the special enrollment period works when you do retire. Getting this wrong in either direction costs money.

Worth knowing before you turn 65

• When your personal enrollment window opens and closes
• Whether your current coverage counts as creditable for Medicare's purposes
• How your spouse's coverage is affected when you switch
• What Parts A, B, D, and supplement plans actually mean for your budget, including IRMAA surcharges if your income is high