Knowing when to sign up for Medicare is essential in the enrollment process. You have a seven-month window surrounding the month you turn 65 to sign up for Medicare Part A and Part B (Original Medicare) to avoid paying higher premiums. Medicare Part C plans serve as optional add-ons to Medicare Parts A, B and D.

There are four main parts of the Medicare benefit:

When Do I Have to Sign Up for Medicare to Avoid Penalties?

When you get close to age 65, it's crucial to start researching your Medicare options. Understanding when to sign up for Medicare benefits helps you effectively manage your health care costs during retirement. You can avoid paying a higher premium for Medicare if you sign up at the right time.

You can sign up for Medicare Part A and Part B during your Initial Enrollment Period (IEP) or during a Special Enrollment Period (SEP) without paying a higher premium for Medicare Part B. You can also choose Medicare Part C and Part D during your IEP or SEP.

If you wait until the General Enrollment Period (GEP) between January 1 and March 31 after missing your IEP, you may have to pay a Part B premium penalty.

When to Sign Up for Medicare: Social Security Benefits

If you receive Social Security benefits or Railroad Retirement Board benefits, you'll be enrolled in Medicare Parts A and B at age 65 automatically. Although the Centers for Medicare and Medicaid Services handle your Medicare benefits, Social Security will enroll you.

You don't have to worry about paying Medicare Part A premiums if you receive Social Security benefits. You may have to pay Part B premiums, depending on your household income and whether you are eligible for assistance.

If you have healthcare coverage through a spouse or domestic partner's insurance plan or you have veteran's benefits, you can choose not to get Medicare Part B. You may have to pay higher premiums if you sign up for Part B later, though.

When to Sign Up for Medicare: No Social Security Benefits Yet

If you aren't already receiving Social Security benefits, you must wait for your IEP to sign up for all parts of Medicare. Your IEP is seven months long. It starts on the first day of the month, four months before turning 65. You have until the last day of the third month after your birthday month to sign up for Medicare.

For example, if your birthday is March 13, your IEP begins December 1 and ends June 30. The exception to the IEP timing rule applies to people with a birthday on the first day of the month. In this case, your IEP moves ahead one month. So, if your birthday is March 1, your IEP is from January 1 to July 31.

When to Sign Up for Medicare: Health Insurance Through Your Employer or Spouse's Employer

If you or your spouse is employed through a company that offers health insurance coverage and you are currently covered under that plan, you can wait to enroll in Medicare Part B. If you file a joint tax return and make less than $174,000 per year, you must pay a premium for Medicare Part B benefits.

The standard monthly premium for Medicare Part B is $144.60 per month, so you'll save $1,735.20 per year if you are eligible to put off getting Medicare Part B. If you aren't covered by an employer's health plan and you don't apply for Medicare Part B during your IEP, you'll pay an extra 10% of the premium for each year you delay.

If your health insurance coverage is through COBRA, because you extended coverage from a previous employer, you still have to sign up for Medicare Part B within your IEP to avoid paying a permanent penalty.

Only those who are currently employed, or have a spouse who is currently employed, and who receive health insurance coverage through that employer, can delay Part B enrollment without a penalty.

When to Sign Up for Medicare Parts C and D

The guidelines for signing up for Medicare Part C and Part D are the same as signing up for Medicare Part A and Part B. Medicare Part C is optional and works as an alternative to Medicare Part A, Part B, and Part D.

Also called Medicare Advantage, Medicare Part C gives you the same coverage as Original Medicare, but you may get additional benefits such as vision and dental coverage. Medicare Part C plans are through private insurers, so the plans have differing out-of-pocket costs. There may also be rules about where you receive health care services.

Do I Have to Sign Up for Medicare When I am 65?

There are penalties for failing to sign up for Medicare Part A and Part B during the seven-month window of time surrounding your 65th birthday.

One of the most important reasons to complete the Medicare sign-up process during your IEP is to avoid paying permanent penalties. Your Part B premiums increase 10% for every 12 months you delay signing up for Medicare past your IEP. If you decide to purposefully delay signing up, you must wait until Medicare's general enrollment period (GEP) between January 1 and March 31 each year.

When to Sign Up for Medicare: Still Working at Age 65

If you are working for a company with at least 20 employees and receiving healthcare benefits through a group health plan on your 65th birthday, you can delay signing up for Medicare Part B. Since Medicare Part A is free, it's a good idea to sign up during your IEP, even if you don't want or need Medicare Part B.

The only reason to delay signing up for free Medicare Part A coverage during your IEP if you are still working at age 65 is if you want to continue contributing to your health savings account (HSA). If you receive Medicare benefits you aren't allowed to set money aside for out-of-pocket health care expenses with your HSA.

When to Sign Up for Medicare: Low Household Income

Even if your household income is low or you qualify for other forms of government aid, you should follow the guidelines about when to sign up for Medicare. You may be able to get help paying your Medicare Part A, Part B and Part D premiums if you qualify for one or more Medicare Savings Programs (MSA).

If you need help paying for Medicare premiums, deductibles, prescription drugs, coinsurance and copayments, apply for aid even if you think your income may exceed the stated limits. Some types of income and assets won't count, making you eligible to get help with medical costs.

Part A premium assistance

The Qualified Disabled and Working Individuals (QDWI) Program helps pay Part A premiums for people who are working, disabled and under the age of 65.

Part A and B premium assistance

The Qualified Medicare Beneficiary (QMB) Program is part of the Medicare Savings Programs (MSA) that helps people with a low household income afford Part A and Part B premiums. You may also receive help paying for coinsurance, deductibles and copayments through QMB.

Monthly income and resource limits apply, and they change each year.

Part B premium assistance

The Qualified Medicare Beneficiary (QMB) Program is a state-run program that helps residents pay for Part B premiums if they are enrolled in Part A and have a household income below the threshold. There is also a resource limit. Even if you receive income from a job, you may still qualify for the QMB Program.

If you don't qualify for Medicaid but still need help paying your Part B premiums, the Qualifying Individual (QI) Program may help pay those costs. You must have Part A and limited income and resources.

QI Program applicants receive benefits on a first-come, first-served basis. If you got QI benefits last year, you have a better chance of getting approved. QI Program participants must apply for benefits every year.

Part D premium assistance

The Part D Low Income Subsidy (LIS), also called Extra Help, is a federal program that makes Medicare Part D's prescription drug program available to those with a low household income if they also have limited assets. LIS and Extra Help reduce or eliminate the Part D premiums due as part of the total cost of Medicare.

The programs lower prescription drug costs and pay your part D premiums up to the amount specified by your state of residence. For example, Californians who qualify for Extra Help can receive up to $32.01 per month to pay for Part D coverage.

If you choose enhanced coverage or you sign up for a Part D plan that costs more than your state's benchmark amount, you are responsible for all charges incurred over the limit. If you missed your IEP and didn't enroll in Medicare Part D, the Extra Help program eliminates your Part D penalty.

If you participate in an MSP, are eligible for Medicaid or get Supplemental Security Income (SSI), you automatically qualify to receive Medicare Part D at no charge.

What if I Don't Sign Up for Medicare at the Right Time?

If you miss your IEP you may not get Medicare coverage for a while, since you'll have to wait until the GEP. This delay could mean you'll be uninsured for a period of time. You may also have to pay ongoing penalties.

If any of the following situations apply to you, it's crucial to sign up for Medicare during your IEP:

• You don't have any other health insurance coverage

• You are covered by insurance you purchased on your own

• You have health insurance through a COBRA plan

• You are covered by your partner in a nonmarital relationship through their employer's insurance plan

• Your healthcare needs are covered by the Department of Veterans Affairs (VA) and you do not have employer-provided health insurance

• Your former employer provides retiree benefits to you or your spouse that include health coverage

How Does Medicare Enrollment Work?

You can enroll for Medicare benefits online at the Social Security website after you are 64 years and nine months old. The process takes about 10 minutes. It's also possible to enroll in Medicare by visiting your local Social Security office in person or by calling 1-800-722-1213.

Since the Social Security Administration already has your personal information, including your address, birth date, and social security number, you don't have to provide documentation during the Medicare sign-up process.

If you don't already have a My Social Security account, you'll create one when you enroll in Medicare. You may need your most recent tax forms and W-2 for identity verification.

While you must sign up for Medicare Part A during enrollment, you can opt out of Medicare Part B, since you may have to pay a premium for Part B services. If you change your mind later you can still enroll in Part B, but you'll pay a premium penalty for delaying enrollment.

After receiving your application, the Social Security Administration will call you if they have any questions or if they need more information. After approval, you'll receive a Welcome to Medicare packet and your Medicare card in the mail.

When Do Medicare Benefits Begin for Me?

Your red, white and blue Medicare card has the date when you can start using your benefits in the lower right-hand corner.

Medicare Part A and Part B coverage are the same for everyone, regardless of where you live in the US. If you have questions about when to sign up for Medicare or how to access Medigap coverage to help pay for health care costs not covered by Medicare Parts A and B, contact a licensed healthcare professional. A Medicare expert can help answer your questions and guide you through the enrollment process.

Rachel Morey is a journalist who has written professionally for nearly a decade, covering insurance and personal finance in print and broadcasting. She lives in Cedar Rapids, Iowa.