Medicare late enrollment penalties can permanently increase your monthly premium for the rest of your life. Understanding these penalties is crucial to avoid costly mistakes in retirement.

Your initial enrollment period is a seven-month window around your 65th birthday, starting three months before you turn 65 and ending three months after. If you’re receiving Social Security benefits, you’ll be automatically enrolled in Medicare Part A and Part B at 65.

The Part B late enrollment penalty is calculated as a permanent 10% increase to your monthly premium for each full 12-month period you delayed enrollment. This penalty is calculated once and then permanently added to your premium for as long as you have Part B coverage. For example, if you delayed enrollment for 24 months, your Part B premium would be 20% higher for life. With the 2026 standard Part B premium at $202.90, a two-year delay would cost you an extra $40.58 monthly forever.

You can avoid penalties if you have creditable coverage through an employer or spouse’s employer plan.