For each month you delay enrollment in Medicare Part D, you will have to pay a 1% Part D late enrollment penalty (LEP), unless you:

In most cases, you will have to pay that penalty every month for as long as you have Medicare. If you are enrolled in Medicare because of a disability and currently pay a premium penalty, once you turn 65 you will no longer have to pay the penalty.

How do you calculate your premium penalty?

Let’s say you delayed enrollment in Part D for seven months (and you do not meet any of the exceptions listed above). Your monthly premium would be 7% higher for as long as you have Part D (7 months x 1%). The national base beneficiary premium in 2018 is $35.02 a month. Your monthly premium penalty would therefore be $2.45 ($35.02 x 1% = $0.3502 x 7 = $2.45) per month, which you would pay in addition to your plan’s premium.

Note: The Part D penalty is always calculated using the national base beneficiary premium. Your penalty will not decrease if you enroll in a Part D plan with a lower premium.