If you have conventional Medicare and are invoiced for Part B premiums on a monthly or quarterly basis and skip one or more payments, here's what happens: The initial billing notice is the standard one that seeks payment by a certain due date, which is the 25th of the month. If you don't pay, you'll get another billing notice about two weeks later. If you still haven't paid, then Medicare will assume you're out of business and won't send you any further notices. If you fail to make a required premium payment within 15 days of its being due, however, then you'll be sent a "delinquent enrollment material" notice. This notice tells you that unless you contact Social Security immediately to put your coverage back in force, you will no longer be covered under Medicare when it re-opens registration next year. After this notice has been sent, you cannot sign up for Medicare coverage until January 1st of the following year. If you don't sign up by then, you'll be charged an early enrollment penalty. The important thing for you to remember is that missing a premium payment can result in losing coverage under Medicare. It's best to pay your premiums in full each time they come due.