A. Congratulations. You are asking the right questions at the right time. The answers will help you prepare for a smooth entry into Medicare.

Most people enroll in Medicare Part A (hospital insurance) and Part B (doctor visits and other outpatient services) during their seven-month initial enrollment period (IEP) around the time they turn 65.

But you can delay enrolling in Part B beyond age 65 without penalty if you have group health insurance from an employer for whom you (or your spouse) are still working. When you retire and this coverage ends, you'll be entitled to an eight-month special enrollment period (SEP) to sign up for Part B without penalty.

This delay is permitted only for people working for companies or organizations that employ 20 or more workers. If you work for a smaller employer, you must enroll in Part A and Part B when you turn 65, and then Medicare pays claims first and your employer plan becomes your secondary insurance.

Medicare has strict enrollment rules that affect people differently according to their circumstances. (See "When Does the Part B Late Penalty Clock Start Ticking?") If you don't sign up within your initial enrollment period or a special enrollment period (whichever is appropriate to you), your monthly premium will permanently increase 10 percent for each 12-month period you were eligible but did not enroll.

Next: If I collect my Social Security at 66, can I still work full time?