People who buy their own health insurance on HealthCare.gov have until Dec. 15 to pick a 2027 plan that starts on Jan. 1. The federal marketplace’s dates and deadlines page sets open enrollment for 2027 coverage to run from Nov. 1 to Jan. 15.

The gap between those two deadlines is what trips people up. Open enrollment lasts until Jan. 15, but a plan chosen after Dec. 15 does not begin on Jan. 1. The HealthCare.gov page says anyone who enrolls or changes plans from Dec. 16 through Jan. 15 gets coverage that starts Feb. 1.

That makes Dec. 15 the date that matters for anyone who needs coverage in place on the first day of the year, such as a person with a scheduled surgery, a regular infusion or a monthly prescription. A household that waits until January would go the month of January with no new coverage if the old plan is ending.

Enrollment dates shift from year to year and from state to state, and The Retirement Money Brief sends the deadlines that matter in one email each weekday.

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Three dates to put on the calendar

• Nov. 1: open enrollment starts. HealthCare.gov says this is the first day to enroll, renew or change plans, and the day to apply for 2027 coverage or update an application with any changes expected for the year ahead.
• Dec. 15: the last day to enroll in or change plans for coverage that starts Jan. 1.
• Jan. 15: open enrollment ends, the last day to enroll in or change marketplace plans for the year.

The December date and the January date are both real deadlines, but they protect different things. Dec. 15 protects a Jan. 1 start. Jan. 15 protects the chance to have a plan at all for 2027.

The cost of a late pick is one month of coverage, not the whole year. Someone who enrolls on Dec. 20 and someone who enrolls on Jan. 14 both start on Feb. 1, according to HealthCare.gov. The healthinsurance.org report gives the same Dec. 15 cutoff for Jan. 1 coverage in HealthCare.gov states.

A shorter season that did not happen

Some readers may have heard that open enrollment would end earlier. HHS finalized a rule in 2025 that would have ended it on Dec. 15 in HealthCare.gov states. According to healthinsurance.org, a judge vacated that rule in June 2026, so the Nov. 1 to Jan. 15 season stands for HealthCare.gov states. The site’s report was last updated in August.

State exchanges set their own dates

Not every state uses HealthCare.gov. The healthinsurance.org report lists several state-run marketplaces with different end dates:

• California, D.C., New Jersey and New York: Jan. 31.
• Massachusetts: Jan. 23.
• Rhode Island: Dec. 31.
• Idaho: Dec. 15.

Anyone in one of those states should use the state exchange’s dates, not the federal ones. The federal dates in this story apply to HealthCare.gov states.

If open enrollment is missed

After Jan. 15, HealthCare.gov says coverage is available only through a Special Enrollment Period, which runs from Jan. 16 through Oct. 31 for people who qualify. HealthCare.gov’s special enrollment page lists qualifying events that include getting married, having a baby, moving to a new ZIP code or county, losing job-based coverage or turning 26. The same page says documents may be required to confirm the event.

The page also notes that people who meet income limits can apply for Medicaid or the Children’s Health Insurance Program outside the normal enrollment windows.

Medicare is a separate calendar

People on Medicare sometimes confuse the marketplace season with Medicare’s own. Medicare’s joining-a-plan page gives Medicare Open Enrollment as October 15 through December 7. That window is for Medicare plans only, and it overlaps the first weeks of the marketplace season.

Getting ready before Nov. 1

The free official route is HealthCare.gov, where applications for 2027 coverage open on Nov. 1. The site offers a downloadable checklist for gathering what the application needs. Before the date arrives, collect the Social Security numbers for everyone in the household, the expected income for 2027, and the current plan’s name and policy number.

The plan to follow is simple: apply early in November if possible, compare plans on the full year’s cost and not only the monthly premium, and finish by Dec. 15 for a Jan. 1 start. A shopper who aims for Dec. 15 leaves a month of cushion before the Jan. 15 end.

HealthCare.gov’s own list of dates, Nov. 1, Dec. 15 and Jan. 15, is the one to rely on if another source gives something different.

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This piece was drafted with AI assistance and edited for accuracy against the HealthCare.gov and Medicare pages linked above.