When does OEP begin?
The Medicare Advantage Open Enrollment Period (MA OEP) runs January 1–March 31 each year, and separately a similar 3-month window applies for someone newly entitled to both Part A and B. There's also a distinct continuous Open Enrollment Period for Institutionalized Individuals (OEPI).
What the rule says
Annual MA OEP (January 1–March 31):
“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.”
The CMS guidance confirms the specific dates:
“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).”
Newly-eligible individual's MA OEP:
“For 2019 and subsequent years, a newly MA eligible individual who is enrolled in a MA plan may change his or her election once during the period that begins the month the individual is entitled to both Part A and Part B and ends on the last day of the third month of the entitlement.”
OEPI (institutionalized individuals), which is continuous rather than a fixed calendar window:
“Occurs: Continuous for an MA-eligible institutionalized individual who moves into, resides in, or moves out of an institution. The OEPI ends two months after the month the individual moves out of the institution (See 42 CFR § 422.2 for definition of "institutionalized").”
This answer relies in part on the CY 2027 enrollment guidance, which applies to enrollment requests received on or after January 1, 2027 (and may be applied by plans to AEP enrollments effective that date).
If you meant a specific client's situation (age-in vs. already-enrolled vs. institutionalized), let me know which case applies.
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?
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