public-service · Medicare Part B late enrollment
Medicare Part B Late Enrollment: The 10% Premium Increase Explained
What the federal regulation says about the structure of Medicare Part B's late-enrollment premium increase and when the General Enrollment Period runs.
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Updated: Sources: 2
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What matters now
- The increase is 10 percent of the standard monthly Part B premium for each full 12-month period of delayed enrollment, as set out in 42 CFR § 408.22.
- The regulation calculates this using enrollment-period rules defined elsewhere in the same regulation, not a flat one-time penalty.
- If you missed your Initial Enrollment Period and don't qualify for a Special Enrollment Period, you can sign up for Part B during the General Enrollment Period: January 1 – March 31 each year.
- This article does not calculate anyone's actual dollar premium, determine Special Enrollment Period eligibility, or address Medicare Part D's separate late-enrollment penalty.
This applies if you missed your Medicare Part B Initial Enrollment Period and don’t qualify for a Special Enrollment Period. In that case, federal regulation adds 10 percent to the standard monthly Part B premium for each full 12-month period of delay, using enrollment-period rules defined elsewhere in the same regulation (eCFR, 42 CFR § 408.22). You can sign up during the General Enrollment Period, which runs January 1 through March 31 each year.
This original record-reading guide is a general reading aid, not cited evidence. It does not depict a source record; the article text and source links provide the facts.
Key points
- The increase is 10 percent of the standard monthly Part B premium for each full 12-month period of delayed enrollment, as set out in 42 CFR § 408.22.
- The regulation calculates this using enrollment-period rules defined elsewhere in the same regulation, not a flat one-time penalty.
- If you missed your Initial Enrollment Period and don’t qualify for a Special Enrollment Period, you can sign up for Part B during the General Enrollment Period: January 1 – March 31 each year.
- This article does not calculate anyone’s actual dollar premium, determine Special Enrollment Period eligibility, or address Medicare Part D’s separate late-enrollment penalty.
What the regulation says
The federal regulation governing this increase, 42 CFR § 408.22, states that “the standard monthly premium determined under § 408.20 is increased by ten percent for each full twelve months in the periods specified in §§ 408.24 and 408.25” (eCFR, 42 CFR § 408.22).
The regulation describes a structure rather than a single dollar amount: it refers to the standard monthly premium and to each full twelve months in the periods specified in §§ 408.24 and 408.25.
Enrolling after a missed window
If the Initial Enrollment Period has already passed and a Special Enrollment Period doesn’t apply to your situation, the Medicare & You 2026 handbook states: “You can sign up for Part B during the General Enrollment Period (January 1–March 31 each year) if you missed your Initial Enrollment Period and don’t qualify for a Special Enrollment Period” (Medicare & You 2026).
The handbook gives January 1 through March 31 as the dates for that enrollment period.
What this article does not answer
This article reports only the quoted increase structure and the handbook’s General Enrollment Period dates. It does not calculate an individual’s premium or determine eligibility for any enrollment period.