Late Enrollment Penalty
If you aren't eligible for premium-free Part A, and you don't buy it when you're first eligible*, your monthly premium may go up 10 percent.
How much is the penalty?
You'll have to pay the higher premium for twice the number of years you could have had Part A, but didn't sign up.
If you were eligible for Part A for two years but didn’t sign up, you’ll have to pay the higher premium for four years.
*May not be applicable if you are eligible for premium-free Part A or if you meet certain conditions that allow you to sign up for Part A during a special enrollment period.