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Identifying when your Medicare coverage begins can actually affect some of the decisions you make about enrolling. For example, if you know that missing your personal enrollment deadline means being able to sign up only during the general enrollment period at the beginning of the year — and that your coverage therefore won’t begin until the following July — you may make an extra special effort to sign up on time.
Or here’s a different example: Say that you delayed Part B because you worked in a job with insurance until long after you turned 65, and now that you’re about to stop work your nice employer is giving you excellent retiree health benefits for the rest of your life. (Hey, it’s rare, but it can happen!)
You decide to sign up for Part B just in case (because no retiree benefits are set in stone) but want to avoid paying premiums for as long as possible. So instead of signing up as soon as you retire, you leave it until the end of the eight-month special enrollment period that you’re entitled to — temporarily saving hundreds of dollars in Part B premiums but avoiding a late penalty.
Depending on the situation, you can sign up for Part A and Part B during any of the following time frames:
During your seven-month initial enrollment period (IEP), in which the middle (fourth) month is the one when you reach age 65 or become eligible for Medicare based on disability
During an eight-month special enrollment period (SEP) granted after you or your spouse stops working for an employer that has provided health coverage you received beyond age 65
During a three-month general enrollment period (GEP) that runs from January 1 to March 31 each year, which you use only if you miss the deadline for your IEP or SEP
Take a look at this table, which shows when your coverage will begin if you sign up in any of the preceding enrollment periods. (Note that this table doesn’t apply to anyone who is automatically enrolled. Also, it applies only to Part A and Part B enrollment.)
| Enrollment Situation | Coverage Begins |
|---|---|
| IEP/When You Turn 65 | |
| During the first 3 months of your IEP | First day of the month in which you turn 65 — or, if your birthday falls on the first day of the month, the first day of the previous month |
| During the 4th month of your IEP | First day of the following month |
| During the 5th month of your IEP | First day of the 2nd month following your enrollment |
| During the 6th month of your IEP | First day of the 3rd month following your enrollment |
| During the 7th month of your IEP | First day of the 4th month following your enrollment |
| SEP/When Covered over 65 by Insurance from a Current Employer | |
| At any time while you have this coverage, provided that your IEP has expired | The first day of the month after you enroll |
| During your 8-month SEP after active employment or insurance ends (whichever comes first) | The first day of the month after you enroll |
| Outside IEP/SEP | |
| During the GEP | The following July 1 |
Source: Social Security Administration
The table shows the big picture stuff. As you can see, the special and general enrollment periods are straightforward. Entitled to a SEP? Your coverage begins on the first day of the month after you enroll. Must enroll during a GEP? Your coverage is delayed for several months until the following July.
But if you sign up during your IEP, the onset of coverage is a bit more complicated and needs more explanation. The IEP — your first chance of signing up for Medicare — always lasts seven months. But when your coverage actually begins depends on which month you enroll.