An elected or appointed official who elected to become a member of the Employees’ Retirement System may receive service credit for previous service as an official with the State or a participating governmental unit including service as an official before the establishment of the Employees’ Retirement System. To receive service credit for previous service, an elected or appointed official shall complete a claim for the service credit and file it with the Board of Trustees on a form the Board of Trustees provides. On receiving a claim for service credit for service as an official with a participating governmental unit, the Board of Trustees shall: verify the previous service and the amount of service credit to which the member is entitled; compute the amount due from the participating governmental unit because of the claim; and submit a statement to the participating governmental unit for that amount. The computation made under paragraph (1)(ii) of this subsection shall be based on the compensation actually received by the official from the participating governmental unit during the period for which service credit is to be granted. A participating governmental unit that receives a statement from the Board of Trustees shall pay the amount immediately to the Board of Trustees or place it in the next budget for prompt payment when that budget becomes effective. On receiving a claim for service credit for service as an official with the State, the Board of Trustees shall: compute the amount due from the State; and include in the State budget for the next fiscal year an appropriation for the amount due from the State. An official who receives service credit under this section: shall pay to the Board of Trustees in a single payment, within the period determined by the Board of Trustees, the member contributions, plus regular interest, that the official would have paid had the official been a member of the Employees’ Retirement System; or subject to paragraph (2) of this subsection, may waive the payment of any part of the member contributions plus regular interest. If an official who receives credit under this section waives payment of any contributions or interest, the Board of Trustees shall reduce the official’s allowance by the actuarial equivalent of those contributions, plus interest to the date of retirement, that the official had not paid.