If you tapped your Social Security benefits before age 65, you’ll automatically be signed up for original Medicare (unless you live in Puerto Rico).
“About a month or two before you turn 65, you’ll be automatically enrolled, and your card will just show up in the mail,” Roberts said.
In this situation, you’ll see your Social Security check reduced by the cost of the Part B premium.
Roberts said that if you already are getting Social Security benefits and you want to delay Medicare because you have qualifying coverage through your employer (see next section), call the Social Security Administration and tell them not to enroll you.
If you haven’t yet tapped Social Security, the burden is on you to sign up. In that case, you get a seven-month enrollment period that starts three months before your birthday month and ends three months after that.