More than 10,000 Colorado residents were wrongly cut off from Medicaid after the state flagged them as potentially ineligible and they didn’t return the paperwork to show they qualified.

This spring, states started going through their Medicaid rolls to determine who was no longer eligible for the first time in about three years. During the emergency phase of the pandemic, states that kept everyone covered received additional federal money. There was an exception for people who left the state or died.

Colorado, like most states, has a program to automatically reenroll households if other data sources, such as applications for food assistance, show their incomes are low enough to qualify for Medicaid. In August, however, the federal Centers for Medicare and Medicaid Services asked states to determine if eligible people were falling through the cracks.

Children and pregnant women can qualify at a higher income than non-pregnant adults. What that means is that even if a household as a whole made too much to qualify for Medicaid, certain members could still be eligible.

The Colorado Department of Health Care Policy and Financing determined 10,044 people who should have qualified were cut off because the system couldn’t verify the entire family was eligible. The state is working on a plan to reinstate them.

About 1.8 million people are covered by Medicaid in Colorado.

Families that might have been ineligible were sent application packets, but some didn’t return them. Some didn’t receive their packets because they had moved, though, or didn’t understand why it was important for them to fill it out, and so lost coverage on procedural grounds.

The Centers for Medicare and Medicaid Services determined 29 states and the District of Columbia were assessing eligibility on the household level, opening up the possibility that they cut off people who qualified.

Now, CMS wants states to automatically reenroll individual members if they would qualify, even if the family might earn too much for the whole household to get coverage. It’s not clear when it will be able to do that, though.

Estimates of the number of people affected varied widely. Maine said no one had been wrongly disenrolled because it had already stopped disenrolling people for procedural reasons, while Nevada and Pennsylvania each estimated more than 100,000 people may have lost coverage in those states because they weren’t automatically reenrolled.

The agency hasn’t announced any penalties if states don’t correct the problem.

“It is very important to us that we ensure the highest level of accuracy for our renewals so that eligible members can stay covered,” state Medicaid director Adela Flores-Brennan said in a statement. “We are implementing this new CMS guidance, and the short-term changes requested as quickly as possible, while also proceeding with thoughtful intentionality to make sure that we are doing it right. We still need our members to pay attention to their mail and email and send in their renewal packets right away.”

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