Health & Medicare
Medicare Part B Late Enrollment Penalty Calculator
Estimates based on CMS's 2026 rate announcement and CMS penalty rules, updated August 2026.
See exactly how much a delayed Part B enrollment will permanently add to your monthly premium.
Data sourced from CMS via Federal Register, Healthline (CMS penalty rules summary)
Your new monthly Part B premium
$0.00
How this is calculated
Source: CMS via Federal Register (2026 standard premium), Healthline summarizing CMS penalty rules (10% per 12-month period) · Last updated 2026-08-19 · See how we calculate this →
See how this compares to the drug-coverage penalty: Medicare Part D Late Enrollment Penalty Calculator (a separate penalty with its own 1%-per-month formula).
How the Part B late enrollment penalty is actually calculated
Medicare Part B has a permanent late enrollment penalty for anyone who was eligible but did not sign up and did not have other creditable coverage, most commonly a current employer's group health plan.
The penalty adds 10% of the standard Part B premium to your own premium for every full 12-month period you went without coverage, and it applies for as long as you have Part B.
The 12-month periods do not round up, which trips a lot of people up. Going 14 months without coverage is one full 12-month period, a 10% penalty, not two.
You would need a full 24 months to reach a second 10% period, taking the penalty to 20%. This calculator applies that same rule: it only counts complete 12-month blocks, not partial ones.
Because the penalty is a percentage rather than a flat dollar figure, its actual cost moves every year the standard premium changes, which is most years. The 2026 standard Part B premium is $202.90 a month, per CMS's official 2026 rate announcement.
A single 10% penalty period on that premium works out to about $20.29 extra a month today, but that number will drift upward as the standard premium rises in future years, since the penalty recalculates against whatever the current premium is.
Not all coverage gaps count against you. If you were covered by a current employer's group health plan, yours or a working spouse's, while you delayed enrolling, that period typically does not trigger a penalty.
You get a Special Enrollment Period to sign up penalty-free within 8 months after that employer coverage or the employment itself ends. COBRA and retiree coverage generally do not count as creditable for this purpose, so leaning on either past your Special Enrollment Period can still trigger the penalty.
If you think you were penalized in error, for example because you had qualifying employer coverage the whole time, you can request that Medicare review the penalty. Keep documentation of your coverage dates on hand, since the burden is generally on you to show the gap should not count.
Frequently asked questions
Is the Medicare Part B late enrollment penalty really permanent?
Yes. Unlike some penalties that phase out, the Part B penalty applies for as long as you have Part B, which for most people is the rest of their life once enrolled.
Does every month I delay count against me?
Only full 12-month periods count, and they do not round up. Delaying 14 months counts as one full period (a 10% penalty), not two. Delaying 23 months is still only one full period.
What if I had employer coverage while I delayed?
Time covered by a current employer's group health plan (yours or a working spouse's) generally does not count against you. The penalty applies to months you went without Part B and without other creditable coverage.
Does the dollar amount of my penalty ever change?
Yes, indirectly. The penalty is a fixed percentage, not a fixed dollar amount, so it moves every year the standard Part B premium changes, typically upward.