Medicare limits when you can join, switch, or drop a Medicare Advantage Plan.
You can join a plan when you first become eligible for Medicare. You will have 3 months prior, the month of, and 3 months after your Parts A & B eligiblilty dates or the month that you turn 65 (or date of disability, if prior to turning 65.) If you have delayed enrollment into Part B, you will only have the 3 months prior to your Part B effective date to enroll into a plan.
You may add, switch or drop Medicare Advantage Plans during the annual election period which is between October 15th and December 7th of each year. You may make as many changes as you like during this period. The last enrollment you submit will be effective January 1st of the following year.
There are other special election periods throughout the year where you may be eligible to add, change or drop a Medicare Advantage Plan. A few examples of these special election periods include change in residence, loss of employer group coverage, and eligibility for Medicaid.