40 ILCS 5/5-166

Whenever any amounts are refunded, the accumulated city contributions shall be transferred to the prior service annuity reserve. If the amounts refunded are repaid, the amount transferred to the prior service annuity reserve shall be credited to the city contribution reserve for the account of the policeman who received the refund, together with interest thereon from the date of the refund to the date or dates of repayment.