The U.S. Senate on Wednesday rejected legislation that would have extended Affordable Care Act (ACA) tax credits, a move that is expected to lead to higher health insurance costs for millions of Americans, including hundreds of thousands of Coloradans, at the start of the new year.

Lawmakers voted on two partisan proposals—one from Democrats that would have extended the enhanced subsidies, and a Republican-backed alternative that focused on creating new health savings accounts. As expected, both measures failed to advance.

Without action from Congress, enhanced ACA tax credits are set to expire, triggering sharp premium increases beginning January 1. In Colorado alone, an estimated 225,000 people who receive coverage through the ACA marketplace are expected to see significant increases in their monthly premiums.

The Colorado Division of Insurance warns that the higher costs could have serious consequences. State officials estimate that as many as 75,000 Coloradans may drop their health insurance coverage altogether because it becomes unaffordable.

The expiration of the tax credits leaves uncertainty for consumers as the new year approaches, with no immediate plan in place to offset rising insurance costs.