This document contains final regulations relating to the income tax imposed under chapter 1, the estate tax imposed under chapter 11, and the gift tax imposed under chapters 12 and 14 of the Internal Revenue Code of 1986. Changes to the marital deduction provisions of the estate and gift tax chapters were made by the Technical and Miscellaneous Revenue Act of 1988. Further amendments were made by the Revenue Reconciliation Act of 1989, and the Revenue Reconciliation Act of 1990. These final regulations will provide guidance needed to comply with the changes to the marital deduction provisions of the estate and gift tax chapters.