Good news for anyone with health insurance: Most surprise medical bills are now illegal. A law that Congress passed more than a year ago went into effect Jan. 1.

Until now, if you had a heart attack or got hit by a car and were taken to an out-of-network hospital, you could end up with some big bills that your insurance wouldn’t cover.

“Our research shows about 1 in 5 emergency visits involves at least one surprise medical bill,” said Karen Pollitz, a senior fellow at the Kaiser Family Foundation.

It’s also common for people to get surprise bills, Pollitz said, even when they go to an in-network hospital for something planned — like a surgery.

“Maybe from the anesthesiologist or the hospitalist who makes rounds,” she said. “You don’t choose those doctors. They work in the hospital, but they don’t work for the hospital.”

And they could bill you separately. But now, they can’t; they have to work it out with your insurance company. 

“The No Surprises Act really is one of the biggest consumer protection laws in the last couple of decades,” said Loren Adler, associate director of the USC-Brookings Schaeffer Initiative for Health Policy.

One kind of surprise bill the law does not cover is ground ambulances. Those can result in an out-of-network bill about 80% of the time.