An open enrollment period from January 1 through March 31 of each year permits people 65 or over who failed to enroll or dropped their Part B Medicare coverage to sign up. Their coverage will begin July 1.

Generally, a 10 percent premium penalty will be added to the monthly premium for each year they could have enrolled but did not. However, if you are covered by an employer or union group health plan through you or your spouse's current or active employment, you may qualify for a special enrollment period.

The special enrollment period allows you to delay enrollment in Part B without paying a premium penalty or waiting for a general enrollment period. You have an eight- month special enrollment period if you have group health plan coverage from current employment at the time you first became eligible for Medicare. This special enrollment period begins with the month employment ends or the month your group health plan coverage ends, whichever comes first.