(1) Prior to July 1, 2021:

(a) Beginning July 1, 2013, and each fiscal year thereafter, the board shall cause an annual actuarial valuation to be performed that will value the plan assets for the year and ascertain the contributions required for such fiscal year. The actuary for the board shall perform the annual valuation of the system on the basis of actuarial assumptions recommended by the actuary, approved by the board, and kept on file with the board using the entry age actuarial cost method. Under this method, the actuarially required funding rate is equal to the normal cost rate, plus the contribution rate necessary to amortize the unfunded actuarial accrued liability on a level percentage of salary basis. The normal cost under this method shall be determined for each individual member on a level percentage of salary basis. The normal cost amount is then summed for all members;

(b) Beginning July 1, 2006, any existing unfunded liabilities shall be reinitialized and amortized over a thirty-year period, and during each subsequent actuarial valuation through June 30, 2021, changes in the unfunded actuarial accrued liability due to changes in benefits, actuarial assumptions, the asset valuation method, or actuarial gains or losses shall be measured and amortized over a thirty-year period beginning on the valuation date of such change;

(c) If the unfunded actuarial accrued liability under the entry age actuarial cost method is zero or less than zero on an actuarial valuation date, then all prior unfunded actuarial accrued liabilities shall be considered fully funded and the unfunded actuarial accrued liability shall be reinitialized and amortized over a thirty-year period as of the actuarial valuation date; and

(d) If the actuarially required contribution rate exceeds the rate of all contributions required pursuant to the School Employees Retirement Act, the actuary shall determine the added contributions required to be paid by the State of Nebraska that constitute the difference between the actuarially required contribution rate and the rate of all other required contributions.

(2) Beginning July 1, 2021, and each fiscal year thereafter:

(a) The board shall cause an annual actuarial valuation to be performed that will value the plan assets for the year and ascertain the contributions required for such fiscal year. The actuary for the board shall perform the annual valuation of the system on the basis of actuarial assumptions recommended by the actuary, approved by the board, and kept on file with the board using the entry age actuarial cost method. Under such method, the actuarially required funding rate is equal to the normal cost rate, plus the contribution rate necessary to amortize the unfunded actuarial accrued liability on a level percentage of salary basis. The normal cost under such method shall be determined for each individual member on a level percentage of salary basis. The normal cost amount is then summed for all members;

(b) Any changes in the unfunded actuarial accrued liability due to changes in benefits, actuarial assumptions, the asset valuation method, or actuarial gains or losses shall be measured and amortized over a twenty-five-year period beginning on the valuation date of such change;

(c) If the unfunded actuarial accrued liability under the entry age actuarial cost method is zero or less than zero on an actuarial valuation date, then all prior unfunded actuarial accrued liabilities shall be considered fully funded and the unfunded actuarial accrued liability shall be reinitialized and amortized over a twenty-five-year period as of the actuarial valuation date; and

(d) If the actuarially required contribution rate exceeds the rate of all contributions required pursuant to the School Employees Retirement Act, the actuary shall determine the added contributions required to be paid by the State of Nebraska that constitute the difference between the actuarially required contribution rate and the rate of all other required contributions.

(3) Upon the recommendation of the actuary to the board, and after the board notifies the Nebraska Retirement Systems Committee of the Legislature, the board may combine or offset certain amortization bases to reduce future volatility of the actuarial contribution rate. Such notification to the committee shall be in writing and include, at a minimum, the actuary's projection of the contributions to fund the plan if the combination or offset were not implemented, the actuary's projection of the contributions to fund the plan if the combination or offset were implemented, and the actuary's explanation of why the combination or offset is in the best interests of the plan at the proposed time.