Internal Revenue Code; Revising the date of adoption of the Internal Revenue Code and other federal income tax statutes for purposes of the state corporate income tax; prohibiting retroactivity of certain Internal Revenue Code amendments; specifying that a limitation, a deduction, an expense, or an amortization may only affect the computation of certain taxable income beginning after a specified date; requiring taxpayers to add to and deduct from taxable income in a specified manner; revising adjustments taxpayers must make to adjusted federal income with respect to certain tax benefits, etc.