WASHINGTON (AP) — About 1.8 million households that got financial help for health insurance under President Barack Obama's law now have issues with their tax returns that could jeopardize their subsidies next year. Administration officials say those taxpayers will have to act quickly.

"There's still time, but people need to take action soon," said Lori Lodes, communications director for the Centers for Medicare and Medicaid Services, which runs HealthCare.gov.

The health care law provides tax credits to help people afford private insurance. Nationally, that aid averages $272 a month, covering roughly three-fourths of the premium. By funneling the aid through the income tax system, Democrats were able to call the overhaul the largest middle-class tax cut for health care in history. But they also spliced together two really complicated areas for consumers: health insurance and taxes. Confusion has been the result for many.

Consumers who got health care tax credits are required to file tax returns that properly account for them, even if they are unaccustomed to filing because their incomes are low. Unless they follow through, "they will not be able to receive tax credits to help lower the cost of their health insurance for 2016," Lodes explained.

Treasury officials said 1.8 million households are at risk of losing subsidies for next year, and that number breaks down as follows:

—About 710,000 households that have not filed a 2014 tax return, although they were legally required to account for health insurance tax credits that they received.

—Some 360,000 households that got tax credits and requested an extension to file their returns. They have until Oct. 15.

—About 760,000 households that got tax credits and filed their tax returns omitted a new form that is the key to accounting for the subsidies. Called Form 8962, it was new for this year's tax filing season.

"I think it was definitely confusing for people," said Elizabeth Colvin of Foundation Communities, an Austin, Texas, nonprofit that helps low-income people with health insurance and taxes. "It could have been worse, quite honestly. I think a lot of tax preparers didn't know how to do these (forms) either."

The 1.8 million households with tax issues represent 40 percent of 4.5 million households that had tax credits provided on their behalf and must account for them. The rest had their returns successfully processed by the IRS as of the end of May.

Earlier this summer, a Supreme Court decision preserved health care tax credits for consumers in all 50 states, turning back a challenge from conservatives opposed to "Obamacare." Because of the law's built-in complexity, some of those consumers may now be at risk of losing their assistance.

Administration officials say they're working hard to prevent that. An estimated 16 million people have gained health insurance since HealthCare.gov opened for business in late 2013, and the White House does not want any slippage.

The IRS has started reaching out to consumers with tax issues. HealthCare.gov is reporting an increase in tax-related calls to its consumer assistance center. That telephone number is 1-800-318-2596. The Health and Human Services department plans another outreach campaign in the fall, coordinated with the start of the 2016 sign-up season on Nov. 1.

"What the IRS is doing here is sending these people a not-so-gentle reminder that they need to file or they will put their subsidy at risk," said Mark Ciaramitaro, vice president for tax and health care at H&R Block, the tax preparation company. He cautioned that many consumers will find the process cumbersome, so they should waste no time getting started.

Despite a thinning out of taxpayer services due to budget cuts, IRS Commissioner John Koskinen says the tax-filing season went relatively smoothly, even with the health care law added. Nonetheless, he acknowledged that there's a learning curve for everybody on health care.

"This is the first year for this new provision," Koskinen wrote in a letter to lawmakers last month. "We expect that taxpayers will continue to better understand this process as it becomes more routine."

The administration and the health law's supporters could be doing a better job educating consumers, said Judy Solomon of the Center on Budget and Policy Priorities, which advocates for low-income people.

"There is definitely room for improvement to make sure people understand how it works," she said. "They are getting an advance payment of a tax credit, and to finish the process they need to file a tax return. They have to look at it as a process that is a year long and has multiple steps."