When is the Medicare Advantage open enrollment period and what changes can a client make?
The MA Open Enrollment Period (MA OEP) runs January 1–March 31 each year (or the three months tied to a new client's Part A/B entitlement). During it, a client already in an MA plan can switch to a different MA plan or drop MA coverage to go back to Original Medicare — with a coordinating Part D enrollment if they leave an MA-PD plan for Original Medicare. It does not allow switching from Original Medicare into an MA plan.
This answer relies on the CY 2027 enrollment guidance, which applies to enrollment requests received on or after January 1, 2027.
What the rule says
“(i) For 2019 and subsequent years. Except as provided in paragraphs (a)(3)(ii) and (iii) and (a)(4) of this section, an individual who is enrolled in an MA plan may make an election once during the first 3 months of the year to enroll in another MA plan or disenroll to obtain Original Medicare.”
“An individual who chooses to exercise this election may also make a coordinating election to enroll in or disenroll from Part D, as specified in § 423.38(e) of this chapter.”
“For an election, or change in election, made during an open enrollment period, as described in § 422.62(a)(3) through (5), coverage is effective as of the first day of the first calendar month following the month in which the election is made.”
From the CY 2027 guidance, on timing and permitted changes:
“Occurs: January 1–March 31 every year and for a three-month period upon new entitlement to both Medicare Part A and B (which generally corresponds to an individual's ICEP—see examples below).”
“• Disenrollment from an MA plan (MA-only, MA-PD) in order to switch to Original Medicare (with or without a stand-alone Part D plan)”
“• Enrollment into a different MA plan (MA-only, MA-PD)”
This is a list of changes not permitted during the MA OEP:
“• Switch from Original Medicare to join an MA plan.”
Carrier and FMO rules are often stricter than CMS rules. This tool reports what CMS sources say and is not legal advice. Enrollment guidance shown is the CY 2027 version. Regulation text reflects the CY 2027 marketing rules, which apply to marketing beginning October 1, 2026.
This answer was generated by mapdbot from the sources listed below on September 23, 2026 and checked against them. Regulation text: eCFR as of 09/15/2026. It is for licensed insurance agents, is not legal advice, and does not cover carrier or FMO rules.
Sources cited
Related questions
- Can I enroll this client today, or do they have to wait until AEP?
- When does OEP begin?
- Does a Medicare Advantage plan have to accept my client's application if they apply during the annual election period?
- When do I use IEP vs. ICEP?
- When does an enrollment made during the annual election period take effect?