When Medicare Coverage Begins

Identifying when your coverage begins can affect several of the decisions you make about enrolling. Based on the situation, you can enroll in Part A and Part B during any of the next time frames:

If you want a detailed walkthrough of Medicare parts, enrollment windows, and options, see our Medicare Guide.

• During your seven-month initial enrollment period, the middle month is the one when you reach age sixty-five or become eligible for Medicare based on disability.
• During an eight-month special enrollment period granted after you or your spouse stops working for an employer that provided coverage beyond age sixty-five.
• During a three-month general enrollment period which runs from January 1st to March 31st each year, used only if you miss the deadline for your SEP or IEP.

The First Three Months of Your IEP

The middle month of your IEP is almost always the month in which you turn sixty-five. If you sign up for Parts A and B during any of the first three months of your IEP, your coverage begins on the first day of the month in which you turn sixty-five, regardless of how far into the month your birthday falls.

Medicare Coverage Awarded Retroactively

If you’re under sixty-five and apply for Social Security disability benefits, you generally must wait twenty-four months before becoming entitled to Medicare. If your disability appeal takes a long time and you are granted Medicare coverage retroactively, you have two options:

• You can accept Medicare coverage retroactively and use it to pay for Medicare-covered services you already received and paid for out of pocket. However, you must also pay Part B premiums back to when you were first eligible.
• You can decline backdated Part B coverage, avoiding retroactive Part B premium payments.

Obamacare to Medicare

Millions of people have received health insurance through the Marketplace established under the Affordable Care Act. As many turn sixty-five every day, you may wonder when and how to transition to Medicare — and whether you need to.

Whether You Need to Make the Switch

It may feel easier to do nothing, but weighing the advantages and disadvantages of switching to Medicare versus staying with the Marketplace ensures you make an informed decision.

Must I Switch to Medicare?

The law allows you to keep your Marketplace plan, but you will no longer qualify for subsidies or tax credits once eligible for Medicare. Paying full Marketplace premiums can cost significantly more than Medicare. Delaying Medicare enrollment without qualifying employer coverage may also result in coverage gaps and permanent late penalties.

To estimate how switching affects your long-term finances, try our Retirement Calculator. You may also find our Retirement Planning Checklist helpful.

Insurance Bought Through SHOP

The rules depend on employer size. Under Medicare rules:

• If your employer has twenty or more employees, you may continue employer coverage and delay Medicare enrollment without penalty.
• If your employer has fewer than twenty employees, you must determine whether employer insurance is primary or secondary to Medicare.

Lacking Enough Work Credits for Premium-Free Part A

You may remain on your Marketplace plan until earning enough credits. Compare the full cost of Marketplace coverage and Medicare premiums to determine the most affordable option.

Missed Part B Enrollment — Can You Stay on a Marketplace Plan?

No. If you miss Part B enrollment when required, you risk coverage gaps and late penalties. Marketplace plans generally cannot be sold to individuals enrolled in any part of Medicare, and premium-free Part A is considered qualifying coverage under Marketplace rules.

This Medicare resource was provided by Amerus Insurance Group, a nationwide independent agency that helps seniors confidently compare plan options, control out-of-pocket costs, and enroll with the right coverage for their doctors, prescriptions, and lifestyle. Whether you’re new to Medicare or reviewing your current plan, speak with an Amerus advisor for a free, personalized consultation.