If you delay enrollment into Part A because you or your spouse are actively working and covered by employer insurance, and you earn enough credits by the time you stop working, you won’t have to pay a late-enrollment penalty when you first enroll and can get Part A premium free. But Medicare does not count COBRA or retirement insurance, and if you’ve used one of those coverages, you must pay a penalty. For Part A, this penalty is 10 percent of the highest premium, and you pay it for twice the number of years you weren’t signed up.