Confusion about coverage of cost sharing has led to a pileup of would-be surprise medical bills waiting to be sent out. (Photo: Shutterstock)

Hospitals around the country are afraid to send out hundreds of thousands of bills related to COVID-19 testing. That's because Congress mandated there would be no copays and no out-of-pocket costs for patients. But many employers with self-funded health plans seem to believe they're exempt from the rules.

When testing kits were still scarce, Vanderbilt University Medical Center in Nashville, Tennessee, fired up its clinical labs. It almost single-handedly took over testing in much of Tennessee. Other health systems didn't even try to compete, although the tests were supposed to be covered by insurance.

Related: Coronavirus testing and care: self-funded health plan considerations