(a) General rule: Upon learning of any errors, the board shall correct errors in the retirement system in a timely manner whether the individual, entity or board was at fault for the error with the intent of placing the affected individual, entity and retirement board in the position each would have been in had the error not occurred.

(b) Underpayments to the system: Any error resulting in an underpayment to the system, may be corrected by the member or retirant remitting the required employee contribution or underpayment and the existing employer remitting the required employer contribution or underpayment. Interest shall accumulate in accordance with the legislative rule 162 CSR 7 concerning retirement board Refund, Reinstatement, Retroactive Service, Loan and Correction of Error Interest Factors and any accumulating interest owed on the employee and employer contributions or underpayments resulting from an employer error shall be the responsibility of the participating public employer. The participating public employer may remit total payment and the employee reimburse the participating public employer through payroll deduction over a period equivalent to the time period during which the employer error occurred. If the correction of an error involving an underpayment to the system will result in the system paying the retirant an additional amount, this additional payment shall be made only after the board receives full payment of all required employee and employer contributions or underpayments, including interest.

(c) Overpayments to the system by an employer: When mistaken or excess employer contributions or other employer overpayments have been made to the system, the board shall credit the employer with an amount computed by the board, to be offset against the employer's future liability for employer contributions to the system. If the employer has no future liability for employer contributions to the retirement system, the board shall refund the erroneous contributions directly to the employer.

(d) Overpayments to the retirement system by an employee: When mistaken or excess employee contributions or overpayments, have been made to the retirement system, the board shall have sole authority for determining the means of return, offset or credit to or for the benefit of the individual making the mistaken or excess employee contribution of the amounts, and may use any means authorized or permitted under the provisions of section 401(a), et seq. of the Internal Revenue Code and guidance issued thereunder applicable to governmental plans. Alternatively, in its full and complete discretion, the board may require the existing employer employing the individual to pay the individual the amounts as wages, with the board crediting the participating public employer with a corresponding amount to offset against its future contributions to the plan. If the employer has no future liability for employer contributions to the retirement system, the board shall refund said amount directly to the employer: Provided, That the wages paid to the individual are not considered compensation for any purposes of this article.

(e) Overpayments from the retirement system: If any error results in any member, retirant beneficiary, entity or other individual receiving from the system more than he would have been entitled to receive had the error not occurred the board upon learning of the error shall correct the error in a timely manner. If correction of the error occurs after annuity payments to a retirant or beneficiary have commenced, the board shall prospectively adjust the payment of the benefit to the correct amount. In addition, the member, retirant, beneficiary, entity or other person who received the overpayment from the retirement system shall repay the amount of any overpayment to the retirement system in any manner permitted by the board. Interest shall not accumulate on any corrective payment made to the retirement system pursuant to this subsection.

(f) Underpayments from the retirement system: If any error results in any member, retirant, beneficiary, entity or other individual receiving from the retirement system less than he would have been entitled to receive had the error not occurred, the board, upon learning of the error, shall correct the error in a timely manner. If correction of the error occurs after annuity payments to a retirant or beneficiary have commenced, the board shall prospectively adjust the payment of the benefit to the correct amount. In addition, the board shall pay the amount of such underpayment to the member, retirant, beneficiary or other individual in a lump sum. Interest shall not be paid on any corrective payment made by the retirement system pursuant to this subsection.

(g) Eligibility errors: If the board finds that an individual, employer, or both individual and employer currently or formerly participating in the retirement system is not eligible to participate, the board shall notify the individual and his or her employer of the determination, and terminate participation in the retirement system. Any erroneous payments to the retirement system shall be returned to the employer and individual in accordance with the methods described in subsections (c) and (d) of this section and any erroneous payments from the retirement system to such individual shall be returned to the retirement system in accordance with the methods described in subsection (e) of this section. Any erroneous service credited to the individual shall be removed. Service credit for service prior to the date on which the individual prospectively commences participation in the retirement system shall be granted only if the board receives the required employer and employee contributions for such service, in accordance with subsection (b) of this section, including interest.