Ellington

The federal government is tightening loopholes that let customers on the Affordable Care Act's public insurance exchanges buy coverage outside the law's annual enrollment window.

That could ease a major concern health insurers have about the exchanges.

The Centers for Medicare and Medicaid Services said Wednesday that it will start requiring documentation or proof from people who say they need to buy a plan or change coverage outside that window for reasons like marriage, permanent move or the birth of a child.

Millions of people have used the ACA's state-based exchanges to buy health insurance, and the vast majority do it during an annual enrollment window that starts every fall and runs into January.

UnitedHealth Group and other insurers have said they were getting a lot of expensive customers outside that main window through these special enrollment periods. They suspect that some customers were waiting until they become sick to buy insurance since no one was asking for proof that they did qualify for special enrollment.

Such proof can come in the form of a birth certificate or a marriage license, and insurers require it for coverage purchased off the ACA's public exchanges. But they aren't allowed to ask for that proof from their exchange customers.

The special enrollment documentation will be required for the 38 states that use the federal, HealthCare.gov website for their exchange. The new requirement will unfold over the next several months.

A CMS spokesman said the government has to notify customers about the new requirement, get documentation from them and then verify it.