Medicare Part B Penalty Calculator

Key takeaway: Every full year you delay Part B without a qualifying reason adds 10% to your monthly premium — permanently — and with the 2026 base at $202.90, that's a real and lasting hit to your retirement budget.

What this helps you decide

• The exact monthly dollar increase in your Part B premium based on how many years you delayed enrollment
• How much extra you'll pay annually and over a 10- or 20-year retirement horizon
• Whether your reason for delaying actually qualifies as an exception — and what documentation you'll need to prove it
• The financial difference between enrolling now versus waiting one more year and adding another 10% on top

Who this is for

• Someone who delayed Medicare Part B when they turned 65 and is now trying to understand exactly what they'll owe when they do enroll
• A person calculating the long-term cost of a few years of delay to decide whether to enroll now or wait for a particular enrollment window
• Anyone who had employer coverage at a small company and is now realizing they may not have been protected from the penalty
• A financial advisor or family member helping someone understand the permanent cost impact of a past enrollment decision

Example results

Example 1 — 1 year of delayed enrollment. You turned 65 in 2025 and didn't enroll in Part B for one full year (12 months) without a qualifying reason. That's one 12-month period, so your penalty is 10% of the current Part B premium. In 2026, 10% of $202.90 equals $20.29 per month added permanently to your Part B premium. Your monthly cost becomes $223.19 instead of $202.90. Over 12 months, you'll pay $243.48 more than a neighbor who enrolled on time. Over 20 years of retirement, that single year of delay costs you $4,869.60 in extra premiums — again, at the current premium level, which will almost certainly rise.

Example 2 — 3 years of delayed enrollment. Three full 12-month periods without Part B means a 30% penalty. Thirty percent of $202.90 is $60.87 per month, permanently. Your Part B premium becomes $263.77 per month instead of $202.90. That's $730.44 more per year than someone who enrolled on time. A 20-year retirement with this penalty costs an extra $14,608.80 above baseline — and again, that assumes premiums stay flat, which they won't. The actual extra lifetime cost will be significantly higher.

Example 3 — 5 years of delayed enrollment. Five full 12-month periods means a 50% permanent penalty. Half of $202.90 is $101.45 per month added forever. Your Part B premium becomes $304.35 per month. You're paying $1,217.40 more per year than someone who enrolled on time. Over a 15-year retirement, that's $18,261 in extra premiums from the penalty alone. This is a scenario that plays out most often when someone had individual market coverage or thought retiree coverage from a former employer would count — it doesn't, and five years of delay is more common than people realize.

Sample scenarios

What to do next

• Count the number of full 12-month periods you were without Part B coverage and had no qualifying employer coverage. That count — not the total months, but the full 12-month periods — is what determines your penalty percentage.
• Gather any documentation of creditable employer coverage you had during the gap, such as an employer letter confirming active coverage dates. This is the only way to reduce or eliminate the penalty before it's assessed.
• Enroll during the next available window — General Enrollment Period (January 1–March 31) if you have no qualifying SEP. Waiting even one more full 12-month period adds another 10% permanently.
• If you believe you had qualifying coverage during part of the delay period, contact your State Health Insurance Assistance Program (SHIP) or call Medicare directly at 1-800-MEDICARE before enrolling to dispute the penalty calculation.

Key facts

• The Part B late enrollment penalty is 10% of the monthly Part B premium for each full 12-month period you were without Part B coverage without a valid exemption. In 2026, the base premium is $202.90/month, making each year of delay worth a permanent $20.29/month surcharge.
• The penalty is recalculated against the current standard premium each year, meaning the dollar amount you pay increases over time as the base premium rises, even though your penalty percentage stays fixed at the level set when you enrolled.
• Coverage types that do NOT protect you from the Part B penalty include COBRA, retiree health coverage, individual market plans, VA benefits, and coverage from an employer with fewer than 20 employees. Only active current employer coverage from a company with 20 or more employees provides a valid exemption.

Related decisions

• Late enrollment penalty checker — See the combined impact if you also delayed Part D coverage.
• Part D penalty calculator — Calculate your drug coverage penalty separately if you also had a gap there.
• Initial Enrollment Period calculator — Find your original enrollment window and see how far past it you are.
• When should I sign up for Medicare? — Understand the full picture of enrollment timing if you haven't enrolled yet.