How to add Medicare Part B when you already have Part A

Confirm that this is a Part B-only request

Use this route when Part A is already in place and you previously declined or did not sign up for Part B. If you need initial enrollment in Part A as well, return to SSA’s general Medicare sign-up service.

Before choosing an application, review SSA’s explanation of enrollment periods. Do not treat a Part B application as proof that a particular enrollment window or coverage start date applies to you.

When employer coverage is involved

SSA’s Part B-only page offers an online application route for the special enrollment situation involving an employer group health plan. It also describes fax or mail alternatives.

Have the employment and health-coverage information ready to compare with SSA’s instructions. Ask SSA about your circumstances if the employer coverage, employment end date, or applicable period is unclear. Different types of coverage are not interchangeable for enrollment purposes.

Use the forms for the situation SSA identifies

Follow the official page’s current links and instructions. These forms serve different purposes; do not send all of them simply because they are mentioned together in a guide.

• CMS-40B is the application for enrollment in Medicare Part B.
• SSA also identifies CMS-L564, Request for Employment Information, for the employer-coverage special enrollment route.
• SSA identifies CMS-10797 for certain exceptional-condition special enrollment situations.

If employment evidence is difficult to obtain

SSA’s Part B FAQ describes alternative evidence that may be relevant when an employer cannot complete part of CMS-L564. Read those instructions and contact SSA about what you can supply.

For example, the FAQ discusses records reflecting health-insurance coverage or premium payments. It does not mean any single document automatically establishes special-enrollment eligibility. SSA must review the circumstances and evidence.

Confirm where to send the request

If using the fax or mail route, get the correct local office details through SSA’s locator and follow the enrollment instructions. If you need phone assistance, call 1-800-772-1213; TTY users can call 1-800-325-0778. Keep the submitted form and any receipt or follow-up request together.