(1)(a) Commencing in 1987 the Legislature shall set the rates for the income tax imposed by section 77-2715 and the rate of the sales tax imposed by subsection (1) of section 77-2703. For taxable years beginning or deemed to begin before January 1, 2013, the rate of the income tax set by the Legislature shall be considered the primary rate for establishing the tax rate schedules used to compute the tax.

(b) The Legislature shall set the rates of the sales tax and income tax so that the estimated funds available plus estimated receipts from the sales, use, income, and franchise taxes will be not less than three percent nor more than seven percent in excess of the appropriations and express obligations for the biennium for which the appropriations are made, except that for the biennium ending June 30, 2019, the percentage shall not be less than two and one-half percent nor more than seven percent. The purpose of this subdivision is to insure that there shall be maintained in the state treasury an adequate General Fund balance, considering cash flow, to meet the appropriations and express obligations of the state.

(c) For purposes of this section, express obligation shall mean an obligation which has fiscal impact identifiable by a sum certain or by an established percentage or other determinative factor or factors.

(2) The Speaker of the Legislature and the chairpersons of the Legislature's Executive Board, Revenue Committee, and Appropriations Committee shall constitute a committee to be known as the Tax Rate Review Committee. The Tax Rate Review Committee shall meet with the Tax Commissioner within ten days after July 15 and November 15 of each year and shall determine whether the rates for sales tax and income tax should be changed. In making such determination the committee shall recalculate the requirements pursuant to the formula set forth in subsection (1) of this section, taking into consideration the appropriations and express obligations for any session, all miscellaneous claims, deficiency bills, and all emergency appropriations. The committee shall prepare an annual report of its determinations under this section. The committee shall submit such report electronically to the Legislature and shall append the tax expenditure report required under section 77-382 and the revenue volatility report required under section 50-419.02.

In the event it is determined by a majority vote of the committee that the rates must be changed as a result of a regular or special session or as a result of a change in the Internal Revenue Code of 1986 and amendments thereto, other provisions of the laws of the United States relating to federal income taxes, and the rules and regulations issued under such laws, the committee shall petition the Governor to call a special session of the Legislature to make whatever rate changes may be necessary.