Millions of Americans with insurance through the Affordable Care Act could find themselves locked into health plans they do not want for the coming year because of the Trump administration's schedule for the enrollment season that starts in less than two weeks.

The complication arises when people who already have health plans under the law are automatically re-enrolled in the same plan. In the past, a few million consumers each year have been auto-

enrolled and then were sent government notices encouraging them to check whether they could find better or more affordable coverage.

This time, according to a federal document obtained by The Washington Post, the automatic enrollment will take place after it is too late to make any changes. Auto-enrollment will occur immediately after the last day of the ACA sign-up season, which the Trump administration has shortened, leaving the vast majority of such consumers stranded without any way to switch to a plan they might prefer.

That inability is particularly problematic at the moment, health policy specialists say, because political turmoil surrounding the sprawling health-care law has contributed to spikes in 2018 insurance rates that might catch customers by surprise, as well as widespread public confusion about this fifth year's enrollment season.

The administration's unannounced decision about the nuances of auto-enrollment is part of a pattern in which President Trump's antipathy for the ACA — he erroneously terms its insurance exchanges "dead" — has filtered into a series of actions and inactions that could suppress the number of Americans who receive coverage through the marketplaces for 2018.

The sign-up period is to run from Nov. 1 to Dec. 15 — half the duration of the past three years. Last month, federal health officials announced that they were slashing by 90 percent the money devoted to outreach and advertising aimed at uninsured Americans eligible for ACA coverage and people already covered who need to sign up again. At the same time, funding for enrollment helpers, known as navigators, has been curtailed by about 40 percent.

Last week, Trump took two dramatic steps that are likely to weaken the ACA marketplaces further. He ended billions of dollars in reimbursements to marketplace insurers for discounts the law requires them to provide to lower-income customers for deductibles and other out-of-pocket expenses. And the president signed an executive order that, over time, is likely to make it easier for individuals and small businesses to buy relatively inexpensive health plans that can circumvent consumer protections and medical benefits required under the law.

How the renewal of current customers in ACA marketplaces will be handled is one of several crucial questions about aspects of the imminent enrollment period that have remained murky as Nov. 1 approaches.

According to the document, "Consumer Timelines," from the Health and Human Services Department's Centers for Medicare and Medicaid Services, the agency overseeing ACA marketplaces, the automatic re-enrollment will take place starting Dec. 16, the day after the enrollment season ends. That is the same date as the past three years, but before, when the sign-up period lasted until Jan. 31, consumers had time to go into HealthCare.gov, the website for the federal insurance exchange on which most states rely, and either shop for a more affordable plan or drop their coverage.

Asked about the timing, CMS officials on Friday did not specifically confirm the auto-enrollment date but issued a statement that said: "Similar to Medicare's open-enrollment period, if you miss the deadline to enroll in a plan of your choice, you will not be able to make any changes to your plan until the next coverage year" except for a small number of people eligible for a special enrollment period because of moves, marriages, new babies or other life changes. The statement said that auto-enrollment will happen this year and that "we encourage all consumers to shop and pick a plan that best suits their health-care needs."

Last year, 2.8 million Americans — or nearly one quarter of the 12.2 million with ACA health plans at the end of the enrollment season for 2017 coverage — were automatically re-enrolled. That figure does not include an unknown number who had received auto-enrollment notices and then chose a different health plan.

It remains unclear whether consumers will be notified of when the automatic enrollment will take place — or that they will be unable to make changes afterward. A page on the HealthCare.gov website, containing information on how to keep or change a health plan, says that current ACA customers will receive two notices before Nov. 1 — one from the federal marketplace and the other from their insurer. It does not say what information those notices will contain.

Asked to clarify, CMS officials did not provide details and pointed to an August news release that said the $10 million remaining for outreach efforts, down from $100 million last year, would focus on telling consumers about "the new dates of the open-enrollment period through digital media, email, and text messages."

Consumer advocates and health policy experts, told of the auto-enrollment timing, were critical. "If they find out after Dec. 15 they've been auto-enrolled, there is a real danger people will not be able to pay the premiums — or will drop out," said Cheryl Fish-Parcham, director of access initiatives for Families USA, a liberal consumer-health lobby.

"It was never a good idea to auto-enroll. The advice has always been to come back and shop," said Karen Pollitz, a senior fellow at the Kaiser Family Foundation. But before, consumers could later choose different coverage. "Now that's it. The curtain falls."