How much is the Part B late enrolment penalty?

The penalty is calculated in whole twelve-month blocks and added to your premium for as long as you hold Part B. Two full years without qualifying coverage means 20% on top, every month, for life. Unlike the Part D penalty it does not shrink, and it is recalculated as the standard premium changes.

Coverage from a large employer where you or your spouse is actively working does not count against you, which is why the eight-month special enrolment period exists after that employment ends. COBRA and retiree coverage do not protect you, and that distinction is where most penalties come from.

An estimate for planning, not a quote. Medicare and the Marketplace set your real figures.