The State Comptroller shall deliver an itemized bill for administrative expenses related to investing and managing accounts in the sinking funds incurred during the period from January 1st (or the date of issuance of the sinking fund bonds, if later) to December 31st of each year (or the date on which all sinking fund bonds of the issuer are retired, if earlier) to each issuer for which it maintains a sinking fund. Such bill shall be sent to each issuer on or before February 1st of each year and on the date which is 30 days after the date on which all sinking fund bonds of the issuer are retired. Fees and expenses of any consultants shall be payable only by issuers who have expressly consented to reimburse the State Comptroller for the use thereof. Any expense charged against more than one sinking fund account shall be divided among the sinking fund accounts to which it applies on a pro rata basis based on the average amount on deposit in each such sinking fund account during the preceding year. The issuer shall pay the amount due to the State Comptroller on or before March 15th of each year by the method of payment specified by the State Comptroller in the itemized bill. Prior to reimbursement by the issuers, such administrative expenses shall be paid by the State Comptroller from the State Purposes Fund.