Reviewed September 2026.
The Medicare Part B late-enrollment penalty (LEP) is an extra percentage added to your monthly Part B premium if you delay Part B beyond your initial enrollment period without qualifying coverage that lets you wait. In plain CMS orientation terms, the add-on is often 10% of the standard Part B premium for each full 12-month period you were eligible but not enrolled, and it usually continues for as long as you keep Part B. This page is Part B-specific. The combined Part B/D overview lives at Medicare late-enrollment penalty basics.
Part B LEP vs nearby Medicare add-ons
| Item | What it is | How it differs from Part B LEP |
|---|---|---|
| Part B LEP | Percent bump on Part B for delayed enrollment without a valid delay | Based on how long you waited |
| Part D LEP | Percent bump on drug coverage after 63+ days without creditable drug coverage | Separate clock; can stack |
| IRMAA | Income-related monthly adjustment on Part B/D | Based on MAGI lookback, not delay months: IRMAA |
| Part B deductible | Annual amount before Part B coinsurance | Cost-sharing, not a penalty: Part B deductible |
Medigap premiums do not cancel a Part B LEP on the Medicare bill: What is Medigap. Drug-stage cost sharing is separate: Part D donut hole.
When people can delay Part B without LEP
Many people who are 65+ and covered under a current employer (or spouse’s employer) group plan with enough employees can delay Part B and use a special enrollment period when that coverage ends. Map that path before you skip Part B: Enroll in Medicare with employer coverage. Individual marketplace plans and COBRA are not the same as active large-employer coverage for Part B delay rules. Confirm your facts with Social Security and Medicare.gov.
Worked sketch: two full 12-month periods
Jordan becomes eligible for Part B at 65 in March 2024, drops employer coverage without enrolling in Part B, and finally enrolls during the General Enrollment Period that creates Part B start in 2027 after two full 12-month periods counted toward LEP. A common teaching illustration is a 20% Part B LEP (2 × 10%) on top of the standard Part B premium for as long as Jordan keeps Part B.
| Line on Jordan’s budget | Treat as |
|---|---|
| Standard Part B premium | Base CMS amount for the year |
| Part B LEP (e.g., 20%) | Permanent-looking percent of the standard premium |
| IRMAA (if any) | Separate income surcharge |
| Medigap or Advantage plan premium | Private plan price beside Medicare |
Exact month counts belong on Jordan’s Social Security / Medicare notice, not on a blog estimate.
Checklist
- Confirm whether you are in initial enrollment, a special enrollment after employer coverage, or general enrollment.
- Do not assume COBRA or a marketplace plan protects you from Part B LEP the way active employer coverage can.
- Budget Part B LEP as an ongoing percent, not a one-time fee.
- Keep Part D creditable-coverage letters separate so you do not mix B and D clocks.
- Use Medicare.gov and Social Security (or SHIP) for enrollment timing; ignore cold-call “penalty removal” pitches.
Educational only. Not Medicare advice. Penalty formulas and enrollment periods change; confirm with Medicare.gov, Social Security, and a qualified counselor.