How to Get Medicare Part B Coverage

What Medicare Part B Covers and Who Needs It

Medicare Part B is the medical insurance portion of Medicare that covers doctor visits, outpatient care, lab tests, X-rays, and some preventive services. Unlike Part A, which most people receive automatically at 65, Part B requires you to take action — either during your initial enrollment window or during a later open enrollment period. If you do not enroll when you are first may be able to access, you will pay a permanent penalty on your premiums for as long as you have Part B.

You become may be able to access for Part B the month you turn 65, or the month you have been receiving Social Security Disability Insurance (SSDI) or railroad retirement benefits for 24 months. If you are still working and have health coverage through your employer, you may be able to delay Part B without penalty, but you must meet specific conditions and notify Medicare in writing.

Key Takeaways

You must enroll in Part B during your Initial Enrollment Period (the three months before, the month of, and three months after you turn 65) or pay a permanent 10 percent penalty on your premiums.
You can enroll through Medicare.gov, by phone at 1-800-MEDICARE, by mail using Form CMS-40B, or in person at your local Social Security office.
Part B costs a monthly premium (amounts vary by income), an annual deductible, and 20 percent coinsurance for most services after the deductible is met.
If you are still working with employer coverage, you may delay Part B without penalty, but you must submit a written statement to Medicare confirming your coverage.
If you miss your enrollment window, you can enroll during the General Enrollment Period (January 1 to March 31 each year), but the permanent penalty applies.

Your Enrollment Window and important date

Your Initial Enrollment Period lasts seven months: three months before the month you turn 65, the month you turn 65, and three months after. For example, if you turn 65 in June, your window runs from March through September. Enroll during this window to avoid the permanent penalty.

If you miss this window, you can enroll during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage begins July 1 of that year. However, you will pay a 10 percent penalty on your Part B premium for each full 12 months you were may be able to access but did not enroll. This penalty stays with you for life, even if you drop Part B and rejoin later.

If you are covered by an employer health plan when you turn 65, you may have a different window. You can delay Part B without penalty if you are actively working and covered by your employer's plan (or your spouse's plan if they are still working). When you leave that job or lose the coverage, you have eight months to enroll in Part B without penalty. You must document your employer coverage in writing to Medicare.

How to Enroll in Part B

You have four main routes to enroll. The fastest is online at Medicare.gov. Go to the "Sign Up for Medicare" section, create or log into your Medicare.gov account, and follow the prompts. You will need your Social Security number and information about any current health coverage. Enrollment is usually processed within a few days.

You can also call 1-800-MEDICARE (1-800-633-4227) and speak to a representative. They can enroll you over the phone and answer questions about costs and coverage. The line is open 24 hours a day, seven days a week. Have your Social Security number and any employer coverage details ready.

If you prefer to enroll by mail, request Form CMS-40B from Medicare or read it from Medicare.gov. Fill it out, sign it, and mail it to the address on the form. Mail enrollment takes longer — allow two to four weeks for processing.

You can also visit your local Social Security office in person. Bring your Social Security card, proof of citizenship or legal residency, and proof of your date of birth. Staff there can enroll you on the spot. Find your local office at ssa.gov or call 1-800-772-1213.

What Part B Costs

Part B has three cost components: the monthly premium, the annual deductible, and coinsurance. The monthly premium varies based on your income. Most people pay the standard amount, but if your modified adjusted gross income exceeds certain thresholds, you pay more. Income thresholds and premium amounts change each year, so check Medicare.gov for current figures.

The annual deductible is the amount you pay out of pocket before Part B coverage begins. Once you meet the deductible, you typically pay 20 percent coinsurance for most services — doctor visits, lab work, imaging, and outpatient procedures. Some preventive services (like annual wellness visits and certain screenings) are covered at no cost after you meet the deductible.

If you cannot afford the premiums or cost-sharing, you may be able to get help through Medicaid or a Medicare Savings Program run by your state. These programs pay some or all of your Part B premium and cost-sharing. Contact your state Medicaid office or call 1-800-MEDICARE to learn whether you may have access to.

Documents You Will Need

Enrollment requires basic identity and citizenship information. Have these documents ready before you start:

Your Social Security number
Proof of U.S. citizenship or legal residency (passport, birth certificate, naturalization papers, or permanent resident card)
Proof of your date of birth (birth certificate, passport, or driver's license)
Information about any current health coverage (employer plan, TRICARE, VA benefits, or other insurance)
Your Medicare number (if you already have one from Part A)

If you are delaying Part B because of employer coverage, you will also need to provide written confirmation of that coverage. Your employer's human resources department can supply a letter stating your coverage dates and that you are actively employed.

What Happens After You Enroll

Once you enroll, Medicare processes your request and sends you a Medicare card in the mail within two to four weeks. Your card shows your Medicare number and which parts of Medicare you have (Part A, Part B, or both). Keep this card with you when you see doctors or go to the hospital.

Your Part B coverage begins on the first day of the month after you enroll, unless you enroll during your Initial Enrollment Period, in which case coverage can begin as early as the month you turn 65. If you enroll during the General Enrollment Period (January through March), coverage does not begin until July 1.

Your monthly premium is deducted automatically from your Social Security check, railroad retirement benefit, or SSDI payment. If you do not receive any of these, Medicare sends you a bill. You can change your payment method at any time through your Medicare.gov account or by calling 1-800-MEDICARE.

Common Mistakes to Avoid

The biggest mistake is missing your Initial Enrollment Period. Even one month late triggers the permanent 10 percent penalty. If you are still working with employer coverage, do not assume you can enroll later without penalty — you must notify Medicare in writing that you have employer coverage, or the penalty applies.

Another common error is confusing Part B with Part D (prescription drug coverage). Part B covers doctor and outpatient services; Part D is separate and covers medications. You enroll in Part D during a different window, usually in October and November each year.

Do not wait until you are sick to enroll. If you delay past your enrollment window, you will pay the penalty even if you never use Part B services. Enroll as soon as you are may be able to access, even if you are healthy and think you will not need it.

Frequently Asked Questions

Can I enroll in Part B after I turn 65 if I missed my window?

Yes, you can enroll during the General Enrollment Period (January 1 through March 31 each year), and coverage begins July 1. However, you will pay a 10 percent penalty on your Part B premium for each full 12 months you were may be able to access but did not enroll. This penalty is permanent.

What if I am still working at 65 and have health insurance through my job?

You can delay Part B without penalty if you are actively working and covered by your employer's health plan. When you leave that job or lose the coverage, you have eight months to enroll in Part B without penalty. Send Medicare a written statement confirming your employer coverage to protect yourself from the penalty.

Do I need Part B if I have a Medigap or Medicare Advantage plan?

Yes. Both Medigap and Medicare Advantage plans require you to have Part A and Part B. You cannot use these supplemental plans without Part B enrollment. Part B is the foundation of your Medicare coverage.

How much does Part B cost per month?

The standard Part B premium changes each year. Most people pay one amount, but if your income is higher, you pay more. Check Medicare.gov or call 1-800-MEDICARE for the current premium. You will also pay an annual deductible and 20 percent coinsurance for most services.

What if I cannot afford the Part B premium?

Your state may offer a Medicare Savings Program that pays some or all of your Part B premium and cost-sharing. You may also be may be able to access for Medicaid. Contact your state Medicaid office or call 1-800-MEDICARE to see whether you may have access to for financial help.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.