This document contains final regulations relating to the payment of rewards under section 7623(a) of the Internal Revenue Code for detecting underpayments or violations of the internal revenue laws and whistleblower awards under section 7623(b). The guidance is necessary to clarify the definition of proceeds of amounts collected and collected proceeds under section 7623. This regulation provides needed guidance to the general public as well as officers and employees of the IRS who review claims under section 7623.