A train wreck has occurred on the way to health coverage for all in the U.S. Forty percent of households that received subsidies for their coverage in 2015 haven’t properly filed 2014 tax returns yet and, in theory, won’t be able to apply for a subsidy in 2016 as a result.

That’s what the Treasury Department determined after comparing tax filers with those who’d received subsidies. A report from the Associated Press/Washington Times said the Treasury identified the problem when reviewing tax records of the 4.5 million households that got subsidies. Of the 1.8 million who are at risk of losing subsidies:

• 760,000 filed their tax forms but didn’t include Form 8962, the subsidy tracking form;

• 710,000 simply didn’t file a tax return;

• 360,000 requested an extension.

The Internal Revenue Service, in an attempt to address the issue, wrote to those who hadn’t yet filed by July, suggesting they do so within 30 days in order to preserve their subsidies.

There’s also been a lag in coordinating tax filings between the Treasury and other departments involved in health care reform tracking due to the addition of Form 8962.