Generally you’re eligible to enroll in Medicare when you turn 65 (in fact, if you are collecting Social security benefits, you are automatically enrolled in Medicare A & B). Some people are eligible at a younger age due to a disability. If you are determined to be disabled, you will be automatically enrolled in Medicare A & B.
For simplicity, let’s look at the timelines for someone turning 65. You can start the enrollment process up to 3 months before your 65th birth month. If you are not collecting your Social Security retirement benefits, you can enroll online at www.ssa.gov or in person at your local Social Security Office.
If you are not covered under an employer plan, you will need to enroll in BOTH Medicare A & B to avoid penalties.
If you are still working and are covered under an employer plan (or you are the dependent of an ACTIVE employee), you can delay your Part B enrollment – when you retire, you can enroll in Part B with no penalties. NOTE: You should always check with Social Security to make sure you can delay your enrollment!