Most people I know are looking forward to signing up for Medicare just as soon as they can.

When you’re first eligible for Medicare, you have a seven-month Initial Enrollment Period to sign up for Medicare’s Part A and/or Part B benefits and services. Part A covers hospitalization and Part B covers doctor visits, outpatient care, and other medical goods and services.

Many people become eligible on their 65th birthday. Those folks can sign up during the seven-month period that begins three months before the month they turn 65, includes the month they turn 65, and ends three months after the month they turn 65.

But what happens if you miss that window?

If you didn’t sign up for Part A and/or Part B (for which you must pay premiums) when you were first eligible, and you aren’t eligible for a Special Enrollment Period (more on that below), you can sign up during the General Enrollment Period between Jan. 1 and March 31 each year.

Your coverage will start July 1. However, you may have to pay a higher premium for late enrollment in Part A and/or Part B.

How do you actually enroll? You can call Social Security (1-800-772-1213) or visit a local Social Security office. Or you can apply online at www.ssa.gov.

After your Initial Enrollment Period ends, you may have the chance to sign up for Medicare during a Special Enrollment Period.

If you’re covered under a group health plan based on current employment, you have a Special Enrollment Period to sign up for Part A and/or Part B any time as long as you or your spouse (or family member if you’re disabled) are working, and you’re covered by a group health plan through the employer or union based on that work.

You also have an eight-month Special Enrollment Period to sign up for Part A and/or Part B that starts the month after the employment ends or the group health insurance based on current employment ends, whichever happens first. Usually, you don’t pay a late enrollment penalty if you sign up during a Special Enrollment Period.

Important Note: COBRA and retiree health plans aren’t considered coverage based on current employment. You’re not eligible for a Special Enrollment Period when such coverage ends. This Special Enrollment Period also doesn’t apply to people with End-Stage Renal Disease (ESRD).

You may also qualify for a Special Enrollment Period for Part A and Part B if you’re a volunteer, serving in a foreign country.

Some people get automatically enrolled in Medicare. Among them are people with certain disabilities and those who are already getting benefits from Social Security or the Railroad Retirement Board.

If you’re automatically enrolled, you’ll get your red, white, and blue Medicare card in the mail three months before your 65th birthday or your 25th month of disability.

Also, Social Security is now processing some Medicare enrollments for same-sex spouses, including:

* Enrollments for premium-free Part A for uninsured spouses age 65 or older based on the work history of a current or former spouse;

* Enrollments for people with End Stage Renal Disease based on the work history of a current or former spouse;

* Reductions in Part A premiums based on the work history of a current or former spouse;

* Requests for Special Enrollment Periods based on group health plan coverage from current employment of a same-sex spouse;

* Reductions in late-enrollment penalties based on group health plan coverage from current employment of a same-sex spouse.

David Sayen is Medicare’s regional administrator for Arizona, California, Hawaii, Nevada, and the Pacific Territories. You can get answers to your Medicare questions 24/7 by calling 1-800-MEDICARE (1-800-633-4227).