This document contains final Income Tax Regulations relating to the determination of effectively connected income under section 864 and final and temporary Income Tax Regulations relating to the branch profits tax and branch-level interest tax under section 884 of the Internal Revenue Code of 1986 (Code). Section 884 was added to the Code by section 1241 of the Tax Reform Act of 1986. This document also contains conforming changes to sections 861, 871 and 897.