35 ILCS 120/6a
Claims for credit or refund shall be prepared and filed upon forms provided by the Department. Each claim shall state: (1) The name and principal business address of the claimant; (2) the period covered by the claim; (3) the total amount of credit or refund claimed, giving in detail the net amount of taxable receipts reported each month or other return period used by the claimant as the basis for filing returns in the period covered by the claim; (4) the total amount of tax paid for each return period; (5) receipts upon which tax liability is admitted for each return period; (6) the amount of receipts on which credit or refund is claimed for each return period; (7) the tax due for each return period as corrected; (8) the amount of credit or refund claimed for each return period; (9) reason or reasons why the amount, for which the claim is filed, is alleged to have been paid in error; (10) a list of the evidence (documentary or otherwise) which the claimant has available to establish his compliance with Section 6 as to bearing the burden of the tax for which he seeks credit or refund; (11) payments or parts thereof (if any) included in the claim and paid by the claimant under protest; (12) sufficient information to identify any suit which involves this Act, and to which the claimant is a party, and (13) such other information as the Department may reasonably require. Where the claimant is a corporation or limited liability company, the claim filed on behalf of such corporation or limited liability company shall be signed by the president, vice-president, secretary or treasurer, by the properly accredited agent of such corporation, or by a manager, member, or properly accredited agent of the limited liability company.
A claim for credit or refund shall be considered to have been filed with the Department on the date upon which it is received by the Department. Upon receipt of any claim for credit or refund filed under this Act, any officer or employee of the Department, authorized in writing by the Director of Revenue to acknowledge receipt of such claims on behalf of the Department, shall execute on behalf of the Department, and shall deliver or mail to the claimant or his duly authorized agent, a written receipt, acknowledging that the claim has been filed with the Department, describing the claim in sufficient detail to identify it and stating the date upon which the claim was received by the Department. Such written receipt shall be prima facie evidence that the Department received the claim described in such receipt and shall be prima facie evidence of the date when such claim was received by the Department. In the absence of such a written receipt, the records of the Department as to when the claim was received by the Department, or as to whether or not the claim was received at all by the Department, shall be deemed to be prima facie correct upon these questions in the event of any dispute between the claimant (or his legal representative) and the Department concerning these questions.
35 ILCS 120/6a