OEP- Takes place between Jan 1st – Mar 31st. During this time, people who have a Medicare Advantage plan will be able to do the following. You may change to another Medicare Advantage plan, drop your Medicare Advantage plan and go back to original Medicare, pick up and stand alone Part-D plan. You are only able to make one change in this time frame and the plans will start on the 1st of the following month. Example: If you sign up on March 3rd, policy will start April 1st.