If you thought ban-the-box regulations were complicating the background screening industry well you’ve obviously missed the many states who have enacted pay history laws. 

how common is it and for what reasons would they be performed?

We all are familiar with running background checks on prospective employees, but how common is it to run background checks on current employees? First of all, you should know that running a background check on any employee at any stage is perfectly legal as long as the procedures for running background checks are still properly in place.