ACA Open Enrollment 2027: Prep in October, Save Later

If you buy your own health insurance, your most expensive month is not January. It is this one, quietly, if you waste it. Open enrollment for 2027 marketplace coverage runs from November 1, 2026 through January 15, 2027 in most states, according to HealthCare.gov guidance summarized by healthinsurance.org. The date that actually governs your life is December 15: enroll or switch by then and your new plan starts January 1. Enroll between December 16 and January 15 and coverage does not start until February 1, leaving you a month on last year's plan or no plan at all.

Why 2027 is not a year to auto-renew

KFF's analysis of 2027 insurer rate filings, covering 276 insurers in all 50 states and DC, puts the median proposed premium increase at about 15 percent. The spread is wide: weighted proposals run from under 7 percent in Vermont, Iowa, and Utah to 29 percent in Arizona. These are proposals under state review, not final rates, but the direction is not in doubt.

Figure 1: Proposed 2027 marketplace premium changes. Source: KFF analysis of insurer rate filings, via Medical Daily, September 2026.

The second change is quieter and bigger for many households. The enhanced premium tax credits that ran from 2021 through 2025 expired on December 31, 2025 and have not been renewed, so for 2027 the credit again follows the pre-2021 limits: household income between 100 and 400 percent of the federal poverty level. That restores the 400 percent cliff, where a raise, a bonus, or side-business income that pushes your estimate over the line drops the credit to zero. The income number you enter at enrollment is what sets your monthly premium, so estimating it carelessly is the most expensive typo of your year.

The October prep list I would actually do

First, build your income estimate on paper: last year's return, plus every change you already know about for 2027, written down. Second, list your doctors, your prescriptions, and your pharmacy, because networks and formularies change even when the plan name does not. Third, gather the documents enrollment asks for: income records, immigration or citizenship documents if they apply, and your current plan details. Fourth, put December 15 on your calendar as the deadline, not January 15. January 15 is the trap door date; December 15 is the plan.

One scheduling note that prevents a common mix-up: Medicare's annual enrollment period, October 15 to December 7, is a completely separate system for people 65 and older, run through Medicare, not HealthCare.gov. Households with one spouse on each system have two different deadlines in the same kitchen. Do not let one stand in for the other.

There was also real uncertainty about this window earlier in the year: a 2025 federal rule would have shortened open enrollment, but a judge vacated that change in June 2026, and HHS has confirmed the November 1 to January 15 window for states using HealthCare.gov, per healthinsurance.org's tracking. If you use a state-run marketplace, confirm your state's dates, since a few set their own.

FAQ

When is ACA open enrollment for 2027 coverage? November 1, 2026 through January 15, 2027 in most states. Enroll by December 15, 2026 for coverage starting January 1, 2027; later enrollments start February 1.

How much are marketplace premiums rising for 2027? The median proposed increase is about 15 percent, according to KFF's analysis of filings from 276 insurers, with proposals ranging from under 7 percent in Vermont, Iowa, and Utah to 29 percent in Arizona. Final rates follow state review.

What happened to the enhanced premium tax credits? They expired on December 31, 2025 and have not been renewed. For 2027, credits again follow the 100 to 400 percent of federal poverty level range, restoring the 400 percent cliff.

Is this the same as Medicare open enrollment? No. Medicare annual enrollment runs October 15 to December 7, 2026 through Medicare. The ACA marketplace window is separate and runs through HealthCare.gov or your state marketplace.