This document contains final regulations regarding the use of designated summonses and related summonses and the effect on the period of limitations on assessment when a case is brought with respect to a designated or related summons. These final regulations reflect changes to section 6503 of the Internal Revenue Code of 1986 made by the Omnibus Budget Reconciliation Act of 1990 and the Small Business Job Protection Act of 1996. These final regulations affect corporate taxpayers that are examined under the coordinated industry case (CIC) program and are served with designated or related summonses. These final regulations also affect third parties that are served with designated or related summonses for information pertaining to the corporate examination.