Chris Hall, an attorney with the Ruby Tuesday case, said many tipped workers aren’t aware of the Department of Labor rule that they should spend no more than 20 percent of their time doing untipped work like wiping tables and polishing silverware.

According to the U.S. Department of Labor’s Wage and Hour division, between 2013 and 2015, investigators found tip credit violations in over 1,500 cases, resulting in nearly $15.5 million in back wages.

But workers and advocates say many people are afraid to complain about problems.

Darron Cardosa, a server in New York City who blogs under the pseudonym “The Bitchy Waiter,” said some side work is a necessary evil but it can easily become excessive.

“You just suck it up,” he said. “If you complain too much, maybe you won’t get as good a shift next week, or maybe you’ll get sent home early.”

It is illegal for employers to fire workers for complaining about labor issues “but they can find another way to make you regret it, or another reason to fire you,” he said.