IRMAA Basics
Understanding Medicare Enrollment Rules with Employer Coverage
Verified against SSA POMS as of September 14, 2026
The short answer
Medicare enrollment can depend on employer coverage status. If you have creditable employer group health coverage, you can delay Medicare enrollment without penalty. Group health plans with less than 20 employees are generally not considered to be creditable with exceptions in the case of certain multi employer health plans. Special Enrollment Periods (SEP) can apply if coverage ends; penalties may arise from mistakes.
General Enrollment Guidelines with Employer Coverage
Individuals who are eligible for Medicare but have employer coverage can typically delay enrolling in Medicare Part B without penalty. This is particularly applicable when the employer has 20 or more employees — known as the 'working aged' provision, where Medicare acts as a secondary payer in the case of employer group health plan (EGHP) coverage. However, if the employer has fewer than 20 employees, the person may need to enroll in Medicare to maintain coverage since the EGHP won't be required to pay first. There is a possible exception to this 20 employee rule in the context of a multi-employer group health plan. If at least one member employer in the plan has 20 or more employees, an exception can be requested from CMS. If granted, an employee whose company has fewer than 20 employees may be able to remain on the multi-employer health plan upon reaching Medicare eligibility age. Employees should check with their employer to verify the health plan’s status and any applicable restrictions.
CMSPDF:medicare/eligibility-and-enrollment/medicare-and-the-marketplace/downloads/medicare-marketplace_master_faq_4-28-16_v2.pdf View source ›Special Enrollment Period (SEP) Criteria
A Special Enrollment Period (SEP) allows individuals to enroll in Medicare after their initial eligibility without penalty under certain conditions, such as when employer-provided health coverage ends. For those who work past 65 and have creditable employer coverage, there is an 8-month SEP to enroll in Medicare Parts A, B, C, and D without late penalties. However, while you have the full 8 months to enroll in Parts A and B, you only have the first 2 months to enroll in Part C or Part D without incurring late enrollment penalties. If you enroll in Part D after the two-month mark, you will face penalties, whether you choose a stand-alone Part D plan or a Medicare Advantage plan with drug coverage. To qualify for the Part B SEP, you must have creditable employer or union health coverage based on current employment. The SEP eight month period begins after your employer coverage ends or you leave your job, whichever occurs first.
CMSPDF:medicare/eligibility-and-enrollment/medicare-and-the-marketplace/downloads/limited-equitable-relief-fact-sheet.pdf View source ›IRMAA and Employer Coverage Considerations
The Income Related Monthly Adjustment Amount (IRMAA) is an additional charge for higher-income beneficiaries on top of their Medicare premium. If you delay enrollment in Medicare due to employer coverage, consider that IRMAA might apply once you enroll in Medicare. If currently facing IRMAA amounts, they typically remain when applied outside of initial enrollments.
CMSPDF:medicare/eligibility-and-enrollment/medicare-and-the-marketplace/downloads/limited-equitable-relief-fact-sheet.pdf View source ›Exceptions for Self-Employed Individuals
Self-employed individuals typically do not count towards an employer's number of employees concerning Medicare secondary payer rules (see section B.2). Special rules might apply if the self-employment status impacts group health plan coverage offered.
HI 00620.177 View source ›Frequently asked
If my employer has less than 20 employees, do I need to enroll in Medicare?
Yes, if your employer has fewer than 20 employees, you typically need to enroll in Medicare when first eligible, as Medicare would be the primary payer. However, there are possible exceptions to this rule in the case of certain multi-employer plans. Individuals should check with their employer to ensure the plan is creditable.
Can I delay enrolling in Medicare if I have employer insurance?
Yes, if your employer has 20 or more employees, you can usually delay Medicare enrollment without penalty under the 'working aged' provision.
How long is the Special Enrollment Period for Medicare A and B when creditable employer health coverage ends?
A Special Enrollment Period (SEP) is an 8-month period allowing you to enroll in Medicare without penalty after your employment or employer health coverage ends. This 8 month SEP is only offered to those who had creditable health coverage, and had worked past 65 and the initial enrollment period. The SEP enrollment period for Medicare C and D is 2 months. The SEP is not available when COBRA or retiree health benefits ends.
Do I pay a penalty if I enroll in Medicare late after losing employer coverage?
Not if you qualify for a Special Enrollment Period (SEP). The SEP for Medicare Parts A and B lasts 8 months. However, for Medicare Advantage and Part D, the SEP is only 2 months. You may face penalties if you don't enroll during your respective SEP.
What happens with IRMAA if I delay Medicare for employer coverage?
IRMAA will not apply until you enroll in Medicare Part B, C, or D. If you delay Medicare enrollment due to employer coverage, IRMAA considerations will begin only once you sign up for these parts of Medicare and your income is above the specified thresholds.