Yes. Missing your Enrollment Period can be costly.
Medicare Part A is premium free if you or your spouse worked and paid taxes for at least ten years. If you do need to pay a premium, the penalty is 10% of the Part A premium for signing up outside of your Enrollment Period. You will have to pay that penalty for twice the number of years you delay enrollment. In other words, if you wait for 4 years to enroll, the 10% premium penalty will need to be paid for 8 years.
If you do not sign up for Medicare Part B when you are first eligible, you will have to pay a 10% premium penalty for every 12 months you delay your enrollment. For example, if your Initial Enrollment Period ended September 30, 2010 and you signed up for Part B during the General Enrollment Period in March 2012, then your Part B premium penalty would be 20%. You waited a total of 30 months to sign up, but that included only two full 12-month periods.
In most cases, the Part B penalty will be attached to your premium for as long as you have Part B coverage.
You enroll in Medicare Part D by buying a standalone prescription drug plan or enrolling in a Medicare Advantage plan that includes drug coverage. This penalty is set by Medicare. For each month you delay, you may pay an additional 1% of the average premium per month. You will pay that penalty for as long as you’re enrolled in a Medicare Part D plan.