I’m turning 65 and have health insurance through my wife’s job. Can I wait until she retires in a few years to sign up for Part B without a late penalty? And how do I prove I was covered?
As long as your spouse’s employer has 20 or more employees, Medicare generally will consider her health coverage “creditable”— meaning that it is a qualifying comprehensive policy—and you can delay signing up for Part B until she retires without any penalty (typically you will have eight months from her retirement date to sign up). But if your spouse works for a firm with fewer than 20 workers, Medicare will be considered your primary health coverage once you reach 65, and you’ll need to enroll in Part B; her policy will then serve as supplemental insurance to fill in any cost gaps. If you don’t enroll in Part B (which covers doctor visits and outpatient services) under those circumstances, you’ll incur a late enrollment penalty when you do.

As to your second question: When you sign up for Medicare Part B, you simply need to provide written evidence that you had been insured by a group health plan to avoid late enrollment penalties. The primary way is to have the employer fill out a CMS-L564 form that confirms you were enrolled (the employer would return that form to you, and you would submit it); you can also submit various other “proof of insurance” documents, such as an email from the employer or the insurer confirming you had been enrolled. One final note: If your spouse decides to return to work and gets creditable health coverage at her new job, you can pause your Medicare Part B benefits and enroll in her new plan. When she retires again, you can reenroll in Medicare Part B with no penalties via the same method.

I belong to a Medicare Advantage plan that covers my prescription drugs. If I switch to original Medicare in the future and I need a Part D prescription drug plan, will I face a late enrollment penalty?
If you drop your Medicare Advantage plan and sign up for original Medicare, you will be able to enroll in a Part D prescription drug plan without incurring a late enrollment penalty. You have two chances to switch: during Medicare’s annual open enrollment period, which always runs from Oct. 15 to Dec. 7, or during the annual Medicare Advantage open enrollment period, from Jan. 1 to March 31. You’ll need to enroll in a Part D plan at the same time you make the switch unless you have other creditable prescription drug coverage, such as from a retiree health plan. If you don’t enroll right away, you would be subject to a late enrollment penalty that grows the longer you delay.

For comprehensive Medicare info and advice, go to aarp.org/mme.