Job-based insurance is insurance offered by an employer or union for current employees and family members. Job-based insurance allows you to delay Medicare enrollment. However, you may want to enroll in Medicare depending on whether your job-based insurance pays primary or secondary. In most cases, you should only delay Part B if your job-based insurance is the primary payer (meaning it pays first for your medical bills) and Medicare is secondary.

If you are eligible for Medicare due to a disability (meaning you are collecting Social Security Disability Insurance) and are covered by your, your spouse’s, or in some cases a family member’s job-based insurance, you have a Special Enrollment Period (SEP) to enroll in Part B up to eight months after you no longer have coverage from current work. This means that you are not required to enroll in Part B when you first become eligible for Medicare (but you must have Part A to keep SSDI). However, remember that in most cases you should only delay Part B enrollment if your job-based insurance is the primary payer.

• Job-based insurance is primary if it is from an employer with 100+ employees. Medicare is secondary in this case, and some people choose not to enroll in Part B because of the additional monthly premium.
• Job-based insurance is secondary if it is from an employer with fewer than 100 employees. Medicare is primary in this case, and if you delay Medicare enrollment, your job-based insurance may provide little or no coverage. You should enroll in Part B to avoid incurring high costs for your care.
  • If you have job-based insurance from a family member and Medicare is primary, you do not have a Part B SEP. You should enroll in Medicare as soon as you are eligible to avoid penalties and gaps in coverage.

Note: There are different rules if you are Medicare-eligible due to age or because you have ESRD.

To find out if your job-based insurance is primary or secondary, contact your or your spouse’s human resources department. If you plan to delay enrollment into Part B and use the SEP later, keep records of your health insurance coverage. You will be required to submit proof of your enrollment in job-based insurance when using the SEP to enroll in Part B. Proof of enrollment in job-based insurance includes:

• Written notice from your employer or plan
• Documents that show health insurance premiums paid, including W-2s, pay stubs, tax returns, and/or receipts
• Health insurance cards with the appropriate effective date

Note: If you have another form of insurance from your employer, like COBRA or retiree insurance, there are different rules for how Medicare works with your plan.