 The Part D penalty is 1% of the average monthly Part D premium for every month that you didn't have coverage and were eligible. This is another reason that you could be penalized for Part D as well. So here's another reason. If you go 63 days or more without coverage, for example, you decide that you don't want to pay the premiums that you've been paying and you take time off from your plan, if you go over 63 days without coverage, you pay the penalty. You'll pay the penalty for as long as you have Part D, and if you stop the coverage, the penalty continues to grow.