Ill. Admin. Code tit. 86 § 160.160
In case the Department determines that the claimant is entitled to a refund, such refund shall be made only from the Aviation Fuel Sales Tax Refund Fund or from such appropriation as may be available for that purpose, as appropriate. If it appears unlikely that the amount available would permit everyone having a claim allowed during the period covered by such appropriation or from the Aviation Fuel Sales Tax Refund Fund, as appropriate, to elect to receive a cash refund, the Department will make such refunds only in hardship cases (i.e., in cases in which the claimant cannot use a credit memorandum). Money from the Aviation Fuel Sales Tax Refund Fund may only be used to make cash refunds for claims of overpayment of tax on aviation fuel paid into the Aviation Fuel Sales Tax Refund Fund. The two most likely situations where this would be the case are the situation in which the claimant has discontinued business and the situation in which the claimant will have a small volume of liability to the Department in the foreseeable future, but receives a large credit memorandum which it therefore might take the claimant a long time to liquidate by using it to pay current taxes. In these instances, the claimant probably would have to sell the credit memorandum at a loss in order to realize anything from it within any reasonable period of time.
Ill. Admin. Code tit. 86, § 160.160