DB4 is the extension given to files used by Paychex Payroll. It is a software from Paychex, which specializes in IT solutions related to human resources, payroll, insurance, human resources and activities in this area on the basis of outsourcing.

DB4 are files used by Payroll to store databases. These databases were supported by a database engine called DBISAM built into the application. Currently, the DB4 format is rarely used and is considered obsolete. This solution has been replaced by more modern tools.