Initial Enrollment Period (IEP)
The IEP begins 3 months before your 65th birthday then ends 3 months later. So, the exact timing of this period is relative to you specifically, so be sure to keep a close eye on your calendar as the time comes nearer.
During the IEP, you can enroll in any Medicare plan you are eligible for, including Original Medicare (Part A and Part B), Medicare Advantage (Part C), Part D, and/or supplements. Keep in mind, however, that the IEP for supplements takes place during the 6 months following your 65th birthday rather than the typical period. You do not have to worry about late penalties if you enroll during your IEP.
Annual Enrollment Period (AEP)
The AEP, on the other hand, takes place from October 15th to December 7th and allows you to add or make changes to your Medicare coverage. Unlike the IEP, however, you cannot enroll in Original Medicare during this time. Keep in mind, however, that you must be enrolled/eligible for Original Medicare before you can make any of these changes:
- Switch from Original Medicare to Medicare Advantage (and vice versa)
- Switch from one Medicare Advantage plan/provider to another
- Switch from a Medicare Advantage plan/provider without prescription drug coverage to an Advantage plan with Prescription Drug(and vice versa)
- Switch from one Prescription Drug plan/provider to another
General Enrollment Period (GEP)
If you did miss your IEP and still need to enroll in Original Medicare, you can do so during the GEP. This period takes place annually from January 1st to March 31st. You can also enroll in additional coverage you are eligible for, but keep in mind that you are limited to one change—so, if you are enrolling in Original Medicare for the first time, you cannot add any other coverage till another opportunity becomes available.
Special Enrollment Period (SEP)
The SEP, unlike the other periods, can take place at any time during the year. You also must be eligible for it in order to use it. Also, you do not have to worry about any late fees with the SEP—besides the IEP, you may incur late fees if you choose to wait till after your IEP ends to enroll.
Automatic Enrollment
As far as Original Medicare is concerned, you will more than likely be automatically enrolled for coverage. You will, however, have to manually find and apply for any additional coverage options. But, for Parts A and B, you should receive a letter informing you of your enrollment during your IEP if you have worked at least 10 years paying Social Security taxes.
You can reject this, however, if you choose to delay your coverage for any reason. Simply follow the instructions on the back of said letter, and/or call the Social Security office.

