When it comes time for you to sign up for Medicare, there's one mistake that can cost you big money.

The federal health care program, which covers 4 million senior and disabled Floridians, provides a specific seven-month enrollment period for Medicare Part A and Part B that is centered around your 65th birthday.

Miss that window of opportunity and there's a good chance of a monetary penalty being tacked onto your monthly Medicare Part B premium – for the rest of your life.

"There are all kinds of [problems] that can happen when it comes to Medicare," said Patty Shaffer, a trainer and research consultant specializing in Medicare for the Florida Department of Elder Affairs. "There isn't a lot of information out there about late enrollment."