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Form CMS-40b: Applying for Medicare Part B


Most Americans enroll in Medicare Part A when they turn 65. Since it comes at no cost to you (provided you’ve paid Medicare taxes), there’s little reason not to. However, not everyone chooses to enroll in part B, as it comes with monthly premiums. If you decide to enroll in part B after already being enrolled in part A, you’ll need to apply with form CMS-40b. For all medicare and retirement planning, consider working with a financial advisor who can help create the right roadmap for you. 

What Is Form CMS-40b?

Form CMS-40b is a form from the Center for Medicare & Medicaid Services that you use when applying for Medicare part B. Medicare part B is insurance coverage from Medicare that covers things like outpatient care, preventive services and medical equipment. It can also cover part-time home health services and physical therapy. Form CMS-40b is only for people who have enrolled in Medicare part A already. If you haven’t enrolled in part A yet, you shouldn’t use this form to apply.

How to Fill Out Form CMS-40b

Filling out the form itself is fairly self-explanatory. You can find a copy of the form on the CMS website. On the form, you’ll need to provide your name, contact information, Medicare number and your signature. You can find your Medicare number on your Medicare card. If you can’t find your card, you can contact the Social Security Administration (SSA) for your number and a replacement card. If you’re unable to sign the form, you can simply write an X in the space provided. You’ll need a witness to sign and date the form if you do this.


How to Submit Form CMS-40b

When you’ve completed the form, you’ll need to mail it or deliver it in person to your local Social Security office. However, you can’t just send in the form at any time. There are three periods during which you can apply to enroll in Medicare part B. The first is your initial enrollment period (IEP).

This takes place starting three months before the month of your 65th birthday, and it ends three months after the month of your 65th birthday, so seven months total. The second period is the general enrollment period (GEP), which takes place between January 1 and March 31 of each year. If you apply during the GEP, you’ll likely have to pay a late enrollment penalty. Plus, your premiums will increase for every year you don’t enroll after you turn 65.

There is a third period during which you can apply for Medicare Part B. It’s known as the special enrollment period (SEP). You can qualify as being in a SEP if you or your spouse is working and receiving group health plan coverage from that work. Your SEP will also extend for eight months after that employment or coverage ceases. If you’re applying during a SEP, then you will need to submit an additional form along with CMS-40b. This additional form is CMS-L564, and you must fill it out and include it with your application.


The Bottom Line

Applying for enrollment in Medicare part B is a fairly straightforward process. The most important factor to consider, as is the case with many things related to Social Security, is when you apply. If you wait to apply until after your IEP and you aren’t eligible for a SEP, you could wind up paying late enrollment penalties and higher premiums. And if you’re applying during a SEP, you’ll need to also include form CMS-L564. Whenever you’re applying, you’ll need to fill out and submit form CMS-40b to get signed up for Medicare Part B.

Tips for Preparing for Your Retirement

  • If preparing for your retirement has your head swimming in acronyms and deadlines, talking with a financial advisor can do a lot to clarify the process. If you don’t have a financial advisor, finding one doesn’t have to be hard. SmartAsset’s free tool matches you with up to three vetted financial advisors who serve your area, and you can interview your advisor matches at no cost to decide which one is right for you. If you’re ready to find an advisor who can help you achieve your financial goals, get started now.
  • Your Social Security benefits can be higher or lower depending on when you first elect for them. To optimize your benefits, use SmartAsset’s Social Security calculator. Just enter your year of birth and your annual income. Then, the calculator can tell you your expected benefit for every year you could possibly elect for benefits.
  • Medical costs are just one part of the retirement picture. To make sure you’re on track to be able to cover all of your retirement expenses, use SmartAsset’s retirement calculator. You can determine how much you need to save to grow your nest egg and support your retirement needs.

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