When a person’s Medicare coverage begins will depend on which enrollment period they choose. The two main enrollment periods are the Initial Enrollment Period (IEP) and the General Enrollment Period (GEP).
In some cases, a person may be eligible to join during a Special Enrollment Period (SEP).
This article will look at when coverage begins and when the different enrollment periods start. It will also cover different ways to enroll and any penalties that may apply for late enrollment.
Glossary of Medicare terms
We may use a few terms in this article that can be helpful to understand when selecting the best insurance plan:
- Out-of-pocket costs: An out-of-pocket cost is the amount a person must pay for medical care when Medicare does not pay the total cost or offer coverage. These costs can include deductibles, coinsurance, copayments, and premiums.
- Deductible: This is an annual amount a person must spend out of pocket within a certain period before an insurer starts to fund their treatments.
- Coinsurance: This is the percentage of treatment costs that a person must self-fund. For Medicare Part B, this is 20%.
- Copayment: This is a fixed dollar amount a person with insurance pays when receiving certain treatments. For Medicare, this usually applies to prescription drugs.
The start of a person’s coverage varies depending on which part they are enrolling in and whether they are eligible for premium-free coverage.
Premium-free Medicare part A enrollment
If a person is eligible for premium-free Part A coverage, they may enroll anytime during or after the IEP begins, and their coverage will start on the first day of their birth month.
If an individual has a birthday that falls on the first of the month, coverage starts the month before their birth month.
ExampleIf a person’s 65th birthday is on June 1st, their IEP would fall between February to August. If they signed up in February, March, or April, the coverage would begin May 1st.
It is possible for those eligible for premium-free Part A coverage to enroll more than 6 months after their birth month. In these cases, Medicare backdates cover to 6 months before a person’s enrollment date.
Paid-premium Medicare Part A and Part B enrollment
If an individual has to pay a premium for Part A in addition to Part B, enrollment should be in the first 3 months they are eligible.
If a persons signs up before the month they turn 65, coverage begins the month they turn 65. If a person signs up in the month they turn 65, or 3 months afterward, coverage beings the next month. For example:
| Enrollment takes place: | Coverage starts: |
| the month a person turns 65 | 1 month after their birth month |
| 1 month after a person turns 65 | 2 months after their birth month |
| 2 months after a person turns 65 | 3 months after their birth month |
| 3 months after a person turns 65 | 4 months after their birth month |
Usually, a person is eligible to enroll with Medicare when they turn 65.
The IEP lasts for 7 months, and starts 3 months before a person turns 65 and 3 months after they turn 65. If a person signs up beyond the IEP, they may need to pay a monthly late enrolment penalty.
Individuals are eligible for Medicare during the IEP, even if they continue working.
A person may delay enrolling for Medicare during the IEP and choose to register during the General Enrollment Period (GEP). This option is possible if the person did not sign up when they were first eligible or were not eligible for a Special Enrollment Period (SEP).
The GEP is the same every year, beginning January 1 and ending March 31.
Medicare resources
For more resources to help guide you through the complex world of medical insurance, visit our Medicare hub.
There are many reasons a person may wish to use the SEP, such as if their union or employer covers them on a group plan or if they or their spouse is working (this can also be another family member if a person has a disability).
Once employment ends or the group health plan ends, whichever happens first, the SEP becomes available for 8 months.
If enrollment occurs within the SEP, Medicare will usually apply not penalty charge for late sign-up.
Penalties may apply if a person does not enroll within the SEPs.
Medicare part A
A person eligible for premium-free Part A may sign up during or after the IEP without any penalty.
An individual who is required to pay a monthly premium for Part A must sign up during the IEP, or they may have to pay a penalty charge.
The late enrollment penalty for Part A is usually 10% of the standard premium. This penalty will be twice the number of years a person delayed enrollment.
For example, if a person were eligible for Medicare in 2022 but did not enroll until 2024, they would have to pay the increased premium for 4 years (the 2 years missed and 2 years penalty).
Medicare part B
A person must enroll for Part B during the IEP. If a person chooses to delay enrollment, they can register during the GEP, but a penalty will apply to the monthly premium. If they sign up under the SEP, there will be no penalty.
The penalty for late enrollment in Part B is 10% of the standard premium for every 12 months a person delays sign-up. In most cases, the penalty lasts as long as a person has Medicare Part B.
The cost of Part B premiums is based on income, but Medicare calculates the penalty using the standard Part B premium in the year a person enrolls.
For example, if a person became eligible for Medicare in 2019, and they chose to enroll in 2024, the penalty calculation works as follows:
| The standard monthly premium increases by 10% for every 12-month enrollment period missed. In 2025 the standard monthly premium is $185 | 10% of $185 = $18.50 |
| Medicare multiplies $18.50 by the number of 12-month enrollment periods missed. In this case, 5 years. | $18.50 x 5 = $92.50 |
| Medicare adds a total of $92.50 to the monthly premium. The new monthly premium is $277.50. | $92.50 + $185 = $277.50 |
Some penalties may be avoidable if a person is eligible for the SEP.
The Medicare enrollment process is automatic when a person receives Social Security benefits, but those who do not must register with Medicare themselves when they become eligible.
People can enroll online by visiting the Social Security Administration website. There is no paperwork to sign or additional documents to submit.
It is also possible to make Medicare applications by phone or teletypewriter (TTY).
Individuals may also apply in person at their local Social Security office after making an appointment.
Those who qualify for premium-free Medicare Part A can enroll anytime during or after the IEP. Their coverage will begin either the first day of their birth month or the first day of the month prior.
If an individual must pay monthly premiums for Part A, coverage begins when registration takes place. If a person delays enrollment by more than 3 months, penalties will apply.
There is also a penalty for people who choose to delay enrollment in Part B by more than 3 months, and the penalty will last as long as a person has Medicare unless they use the SEP.
