Coverage for Medicare Parts A and B is not automatic. You need to apply for it by going to medicare.gov.

• If you retire before or at age 65, it’s best to apply for coverage three months before you turn age 65. You can also apply up to three months after the month in which you turn age 65 without paying a late-enrollment penalty.
• If you continue to work past age 65, it’s best to apply for coverage three months before your retirement month (since the medical coverage you have as an active employee will end at the end of the month in which you retire). You also can apply for Medicare up to eight months after your active employee medical coverage ends without paying a late-enrollment penalty.