In most cases, your health insurance coverage will not take effect immediately. There are general effective date rules that apply each year during open enrollment and during special enrollment periods triggered by qualifying events, which are addressed below.
Open enrollment begins November 1 and continues through at least January 15 in nearly every state (only Idaho opted for a December deadline during the open enrollment period for 2024 coverage; the federal government has proposed a rule change that would require all states to end open enrollment no earlier than January 15 in future years 1 ).
In most states, enrollments completed by December 15 will have a January 1 effective date, and enrollments completed between December 16 and January 15 will have a February 1 effective date.
But several state-run exchanges allow enrollments to be completed as late as December 31 and still have a January 1 effective date. And there are a handful of state-run exchanges that have open enrollment deadlines as late as January 31; for some of them, people who enroll in the latter part of January will have coverage effective March 1.
In addition, if any insurers exit the market or terminate certain plans (replacing PPOs with HMOs, for example) at the end of the year, the people enrolled in those plans will be eligible for special enrollment periods. The special enrollment period, in that case, will run for 60 days before and 60 days after the loss of coverage.
People in this situation who pick a replacement plan before the end of December will have coverage effective January 1 (even if they enrolled after December 15). If they pick a replacement plan in the first 60 days of the new year, their new plan will likely take effect the month after the enrollment is completed, although there is still some state-to-state variation on this.
Outside of open enrollment (ie, if you’re enrolling due to a qualifying event), the rule in most states simply calls for coverage to take effect the month after the enrollment is completed, regardless of the date of the enrollment (so an enrollment completed on August 1 or August 31 would have a September 1 effective date)
Before 2022, the rule in most states required the application to be completed by the 15th of the month to have coverage effective the first of the following month (so for example, an application submitted on July 20 would have had coverage September 1).
That changed as of 2022 in states that use HealthCare.gov, with coverage now effective the month after a special enrollment period application is completed. The 19 state-run exchanges have thus far had the option to switch to the approach HealthCare.gov is using, or to continue with their own effective date rules. (Most of the state-run exchanges historically had a 15th-of-the-month deadline, but the exchanges in Massachusetts and Rhode Island have always allowed people to enroll as late as the 23rd of the month and still have a first-of-the-following month effective date.)
For 2025 and future years, the federal government has proposed a rule change that would require state-run exchanges to use the same protocol that HealthCare.gov uses, with coverage effective the first of the month following enrollment during a special enrollment period. 1
As noted above, most special enrollment period applications have first-of-the-following-month effective dates in most states as of 2022. But the state-run exchanges can set their own rules for this. However, some qualifying events have their own effective date rules, regardless of the state: 2
A few points regarding loss of other coverage: It’s important here to note that your qualifying event date is the last day your old plan is in effect, NOT the first day that you would no longer have coverage (since the new plan will take effect the first of the month following the date of the qualifying event).
If your old plan ends mid-month, and COBRA is an option, you could have your new plan take effect the first of the following month (ie, resulting in a partial month gap in coverage) and retroactively elect COBRA if a medical need were to arise before the new plan takes effect.
If you wait and enroll during the 60 days after your old plan ended, your effective date could be the first of the second following month if you’re in a state that still has a 15th-of-the-month deadline and you sign up after the 15th. If the proposed rule change for 2025 is finalized, states would no longer be able to use a 15th-of-the-month deadline to have coverage effective the first of the following month.
Outside the exchanges, effective dates generally follow the same rules as inside the exchanges. However, some insurers in some states opt to extend the enrollment deadline to December 31 for coverage effective January 1, if the person is applying outside the exchange during open enrollment.
States also have the option to impose stricter limits on open enrollment for off-exchange plans. New Mexico is an example of this, with an off-exchange open enrollment period that ends on December 15, a month before the open enrollment period ends for on-exchange plans. 4
If you’re enrolling in a non-ACA-compliant plan (like a short-term health plan), coverage can be effective as soon as the day after you enroll, but the insurer can use medical underwriting to determine your eligibility for coverage.
Louise Norris is an individual health insurance broker who has been writing about health insurance and health reform since 2006. She has written dozens of opinions and educational pieces about the Affordable Care Act for healthinsurance.org.
