35 ILCS 115/20
If it is determined that the Department should issue a credit or refund hereunder, the Department may first apply the amount thereof against any amount of tax or penalty or interest due hereunder, or under the Service Use Tax Act, the Retailers' Occupation Tax Act, the Use Tax Act, any local occupation or use tax administered by the Department, Section 4 of the Water Commission Act of 1985, subsections (b), (c) and (d) of Section 5.01 of the Local Mass Transit District Act, or subsections (e), (f) and (g) of Section 4.03 of the Regional Transportation Authority Act, from the person entitled to such credit or refund. For this purpose, if proceedings are pending to determine whether or not any tax or penalty or interest is due hereunder, or under the Service Use Tax Act, the Retailers' Occupation Tax Act, the Use Tax Act, any local occupation or use tax administered by the Department, Section 4 of the Water Commission Act of 1985, subsections (b), (c) and (d) of Section 5.01 of the Local Mass Transit District Act, or subsections (e), (f) and (g) of Section 4.03 of the Regional Transportation Authority Act, from such person, the Department may withhold issuance of the credit or refund pending the final disposition of such proceedings and may apply such credit or refund against any amount found to be due to the Department as a result of such proceedings. The balance, if any, of the credit or refund shall be issued to the person entitled thereto.
Any credit memorandum issued hereunder may be used by the authorized holder thereof to pay any tax or penalty or interest due or to become due under this Act, or under the Service Use Tax Act, the Retailers' Occupation Tax Act, the Use Tax Act, any local occupation or use tax administered by the Department, Section 4 of the Water Commission Act of 1985, subsections (b), (c) and (d) of Section 5.01 of the Local Mass Transit District Act, or subsections (e), (f) and (g) of Section 4.03 of the Regional Transportation Authority Act, from such holder. Subject to reasonable rules of the Department, a credit memorandum issued hereunder may be assigned by the holder thereof to any other person for use in paying tax or penalty or interest which may be due or become due under this Act, the Service Use Tax Act, the Retailers' Occupation Tax Act, the Use Tax Act, any local occupation or use tax administered by the Department, Section 4 of the Water Commission Act of 1985, subsections (b), (c) and (d) of Section 5.01 of the Local Mass Transit District Act, or subsections (e), (f) and (g) of Section 4.03 of the Regional Transportation Authority Act, from the assignee.
In any case in which there has been an erroneous refund of tax payable under this Act, a notice of tax liability may be issued at any time within 3 years from the making of that refund, or within 5 years from the making of that refund if it appears that any part of the refund was induced by fraud or the misrepresentation of a material fact. The amount of any proposed assessment set forth in the notice shall be limited to the amount of the erroneous refund.
35 ILCS 115/20