Looking for a few basics on the history and mission of the nation's tax agency? Try these: IRS - An Overview This provides a snapshot of the role and operations of the IRS. IRS Timeline From the Civil War to the 21st century, the tax agency's work has changed with the times. IRS Guidance in Plain English This provides a starting point for understanding some of the basic guidance issued by the IRS. Just remember, we said this is a starting point.