30 ILCS 105/8.4a
Whenever an appropriation act provides that expenditures made pursuant to such appropriation are payable from 2 or more funds in specified proportions, the State Comptroller and State Treasurer shall record all such expenditures as having been made from the fund from which the greater proportion of the appropriations are payable or from the fund designated by the Comptroller if the appropriations are payable from 2 or more funds in equal proportions. Within the first 15 days of each calendar quarter, the Comptroller shall order the Treasurer to transfer to the fund from which expenditures were made, from the other fund or funds from which the particular appropriation is payable, the proportionate amount of the aggregate expenditures of such appropriation within the preceding calendar quarter, which is payable from such other fund or funds under the appropriation Act.
30 ILCS 105/8.4a