The Jock Tax is a colloquial term for a tax imposed on traveling professionals. It got its nickname because all-star athletes are the most well-known “traveling professionals”, who also happen to have very public salaries.
In essence, this tax is a separate income tax an athlete most pay on top of their earnings and salary, based on where they're playing. Its official introduction to the world of sports is debated between 1968 and 1991. In 1968, California was faced with an appeal for taxes owed by a San Diego Charger who didn’t live in the state. In 1991, after the Los Angeles Lakers lost to the Chicago Bulls, California decided to tax Michael Jordan’s winnings specifically. California will once again take a pretty penny of whoever wins the NBA Finals this Sunday. Their jock tax rate is a whopping 13.3%.
Below is an infographic with more info of this tax.