When Is Medicare Required and Who Must Enroll

When Medicare Becomes Required

Medicare is required for most people once they turn 65, and it is also required for younger adults with certain disabilities or end-stage renal disease. If you are entitled to Social Security or Railroad Retirement benefits, you are generally automatically enrolled in Part A and Part B when you reach 65. If you are not receiving those benefits, you must actively sign up during your Initial Enrollment Period, which begins three months before the month you turn 65 and ends three months after.

Who Must Enroll in Medicare

You are required to enroll if you are 65 or older and a U.S. citizen or lawful permanent resident who has lived in the country for at least five continuous years. You must also enroll if you have been receiving Social Security disability benefits for 24 months, if you have ALS, or if you have end-stage renal disease requiring dialysis or a transplant. Even if you are still working past 65 and have employer coverage, you may still be required to sign up depending on the size of your employer's plan.

Exceptions and Special Situations

If you are covered by a current employer group health plan based on that employer's active work, you can delay Part B without penalty until that coverage ends. Similarly, if you are covered by a spouse's active employer plan, you may postpone enrollment. People who are still working and have creditable coverage from an employer with 20 or more employees can safely delay Part B. However, once that employment or coverage ends, a Special Enrollment Period opens, typically lasting eight months.

Penalties for Not Enrolling When Required

If you do not sign up when you are first eligible and you do not have creditable coverage, you will likely face a late enrollment penalty. For Part B, the penalty is an additional 10% on your premium for every full 12-month period you could have had Part B but did not sign up. The penalty applies for as long as you have Medicare. For Part A, late enrollment can mean paying higher premiums, though many people qualify for premium-free Part A based on their work history.

Key Enrollment Periods and Deadlines

• Initial Enrollment Period: 7 months around your 65th birthday
• General Enrollment Period: January 1 to March 31 each year
• Special Enrollment Period: triggered by certain life events, such as losing employer coverage
• Medicare Advantage Open Enrollment: January 1 to March 31

Staying on top of these windows helps you avoid gaps in coverage and financial penalties.