For each 12-month period you delay enrollment in Medicare Part B, you will have to pay a 10 percent Part B premium penalty, unless you have insurance from your or your spouse’s current job.

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 pay premium penalties, once you turn 65, you no longer have to pay the premium penalty.

How do you calculate your premium penalty? Let’s say you turned 65 in 2009, and you delayed signing up for Part B until 2015 (and you did not have employer insurance that allows you to delay enrollment). Your monthly premium would be 60 percent higher for as long as you have Medicare (6 years x 10 percent). Since the Medicare Part B premium in 2015 for most people is $104.90, your monthly premium with the penalty would be $167.84 ($104.90 x 0.6 + $104.90).

Note: Although your Part B premium amount is based on your income, your penalty is calculated based on the standard Part B premium. The penalty is then added to your actual premium amount.