(1)(a) If the board determines that the retirement system has previously received contributions or distributed benefits which for any reason are not in accordance with the statutory provisions of the State Employees Retirement Act, the board shall refund contributions, require additional contributions, adjust benefits, credit dividend amounts, or require repayment of benefits paid. In the event of an overpayment of a benefit, the board may, in addition to other remedies, offset future benefit payments by the amount of the prior overpayment, together with regular interest or interest credits, whichever is appropriate, thereon. In the event of an underpayment of a benefit, the board shall immediately make payment equal to the deficit amount plus regular interest or interest credits, whichever is appropriate.

(b) The board shall have the power, through the director of the Nebraska Public Employees Retirement Systems or the director's designee, to make a thorough investigation of any overpayment of a benefit, when in the judgment of the retirement system such investigation is necessary, including, but not limited to, circumstances in which benefit payments are made after the death of a member or beneficiary and the retirement system is not made aware of such member's or beneficiary's death. In connection with any such investigation, the board, through the director or the director's designee, shall have the power to compel the attendance of witnesses and the production of books, papers, records, and documents, whether in hardcopy, electronic form, or otherwise, and issue subpoenas for such purposes. Such subpoenas shall be served in the same manner and have the same effect as subpoenas from district courts.

(2) The board may adopt and promulgate rules and regulations implementing this section, which shall include, but not be limited to, the following: (a) The procedures for refunding contributions, adjusting future contributions or benefit payments, and requiring additional contributions or repayment of benefits; (b) the process for a member, member's beneficiary, employee, or employer to dispute an adjustment of contributions or benefits; and (c) notice provided to all affected persons. All notices shall be sent prior to an adjustment and shall describe the process for disputing an adjustment of contributions or benefits.