For most of the past decade, Marketplace open enrollment has run into January. People learned that rhythm, and a good number of them enrol in the first week of the new year, after the holidays, when the bills have landed and health insurance is finally the thing in front of them.
That option is gone for 2027 coverage on the federal platform. The window closes on 15 December, and anyone working from memory is going to find it shut.
What actually changed
CMS is direct about it: for Exchanges on the federal platform, the open enrollment period will run from November 1 through December 15 preceding the coverage year, beginning with the open enrollment period for plan year 2027.
That is a month less than many people expect, and the month removed is the one at the end — the part of the window people actually used.
The change comes from the 2025 Marketplace Integrity and Affordability Final Rule. CMS gives four reasons: to reduce consumer confusion, to align more closely with open enrollment dates for many employer-based health plans, to encourage continuous coverage, and to reduce the risk of adverse selection from consumers who might otherwise wait to enrol until they need health care.
Whatever you make of the reasoning, the operative fact is the date.
If your state runs its own Exchange
Not every state uses the federal platform, and the rule leaves state-run Exchanges some room. The final rule allows all Exchanges flexibility to set their own open enrollment periods within set parameters:
- it must start no later than November 1
- it must end no later than December 31
- it may not exceed nine calendar weeks
So a state Exchange can run past 15 December. It cannot run into January.
This matters because national coverage of the change will quote the federal date, and roughly a third of enrollees are not on the federal platform. If you are in a state running its own Exchange, the date to trust is the one your Exchange publishes — not the one in a headline.
Coverage always begins 1 January now
One more detail that removes an option people used to rely on: all enrollments pursuant to the open enrollment period must begin on January 1.
Previously, enrolling in the later part of the window could mean a February start. That is no longer how it works. Whether you enrol on 1 November or 15 December, coverage begins on the same day — which means enrolling early costs you nothing and removes the risk of a site outage or a document problem in the final week.
What to do with the time you have
The window is shorter, so the work is the same and the runway is not. Three things are worth doing before December.
Read what your current plan is doing next year. Premiums, deductibles, provider networks and drug formularies all change annually. A plan with the same name in January is not necessarily the same plan.
Check the plan against the numbers, not the premium. The 2027 out-of-pocket maximum is $12,000 for self-only coverage and $24,000 for other than self-only. That ceiling, the deductible and how the plan treats out-of-network care matter more than the monthly figure — the full picture is in how the four layers of health plan cost actually work.
If your income is modest, look at silver specifically. Cost-sharing reductions attach only to silver plans, and choosing bronze for a cheaper premium forfeits them. That is the single most expensive mistake available during open enrollment, and it is covered in the same guide.
If you miss it
Missing open enrollment generally means waiting for the next one. The exception is a special enrollment period, opened by a life event — losing other coverage, moving, marriage, a birth or adoption among them. These have their own deadlines, usually measured in days from the event rather than months.
Relying on one is not a plan. It is what exists if the plan fails.
What to actually check
- Which Exchange are you on? Federal platform means 15 December. A state Exchange may differ — check the date your state publishes.
- Has your plan sent notice of changes for next year? Read it rather than filing it.
- What is the deductible and the out-of-pocket maximum, not just the premium?
- Would cost-sharing reductions apply to you? If so, silver is the only tier that carries them.
- Diary the date now. The window is nine weeks at most, and the part people habitually used has been removed.
This article sets out the enrollment dates and rules published by CMS. It is not insurance or financial advice, and what plan suits you depends on your income, your household and the care you expect to need. Confirm dates on HealthCare.gov or your state Exchange, since operational detail can change.
Sources
- CMS — 2025 Marketplace Integrity and Affordability Final Rule (opens in a new tab)
- HealthCare.gov — When can you get health insurance? Dates and deadlines (opens in a new tab)
- HealthCare.gov — Renew, change, update, or cancel your plan (opens in a new tab)
- HealthCare.gov — Special enrollment periods (opens in a new tab)
- CMS — Plan Year 2026 Marketplace plans and prices fact sheet (opens in a new tab)
This article is general information for a United States audience and reflects enrollment rules published by CMS at the date of review. It is not insurance, tax or financial advice. Dates and operational details can change, and state-run Exchanges set their own windows within federal limits. Confirm the deadline that applies to you on HealthCare.gov or your state Exchange before relying on any of this. Last reviewed 15 September 2026.
