This document contains final and temporary regulations clarifying that for purposes of allowing a tentative adjustment, the IRS may credit or reduce the tentative adjustment by an assessed tax liability, whether or not that tax liability was assessed before the date the application for tentative carryback was filed, and other unassessed tax liabilities in certain other circumstances. The portions of this document that are final regulations provide technical revisions that remove all references to IRS district director and service center director, as those positions no longer exist within the IRS. The offices of the district director and service center director were eliminated by the IRS reorganization implemented pursuant to the IRS Reform and Restructuring Act of 1998. The text of the temporary regulations serves as the text of the proposed regulations, set forth in the notice of proposed rulemaking on this subject in the Proposed Rules section in this issue of the Federal Register.