The answer
What is the Part B late penalty?
The Part B late penalty is a permanent surcharge added to your Part B (medical) monthly premium if you delay enrolling without qualifying coverage.
The penalty is 10% of the standard premium for each full 12 months you could have had Part B but did not sign up. Because it is based on full 12-month periods, waiting two full years would add 20%, and so on. The surcharge is permanent, meaning it stays on your premium for as long as you have Part B, not just for a year. You can avoid it by enrolling during your Initial Enrollment Period or by having qualifying coverage, like active employer insurance, that lets you delay.