410 ILCS 705/60-20
Each person who is required to pay the tax imposed by this Article shall make a return to the Department on or before the 20th day of each month for the preceding calendar month stating the following:
All returns required to be filed and payments required to be made under this Article shall be by electronic means. Taxpayers who demonstrate hardship in paying electronically may petition the Department to waive the electronic payment requirement. The Department may require a separate return for the tax under this Article or combine the return for the tax under this Article with the return for the tax under the Compassionate Use of Medical Cannabis Program Act. If the return for the tax under this Article is combined with the return for tax under the Compassionate Use of Medical Cannabis Program Act, then the vendor's discount allowed under this Section and any cap on that discount shall apply to the combined return. The taxpayer making the return provided for in this Section shall also pay to the Department, in accordance with this Section, the amount of tax imposed by this Article, less a discount of 1.75%, but not to exceed $1,000 per return period, which is allowed to reimburse the taxpayer for the expenses incurred in keeping records, collecting tax, preparing and filing returns, remitting the tax, and supplying data to the Department upon request. No discount may be claimed by a taxpayer on returns not timely filed and for taxes not timely remitted. No discount may be claimed by a taxpayer for any return that is not filed electronically. No discount may be claimed by a taxpayer for any payment that is not made electronically, unless a waiver has been granted under this Section. Any amount that is required to be shown or reported on any return or other document under this Article shall, if the amount is not a whole-dollar amount, be increased to the nearest whole-dollar amount if the fractional part of a dollar is $0.50 or more and decreased to the nearest whole-dollar amount if the fractional part of a dollar is less than $0.50. If a total amount of less than $1 is payable, refundable, or creditable, the amount shall be disregarded if it is less than $0.50 and shall be increased to $1 if it is $0.50 or more. Notwithstanding any other provision of this Article concerning the time within which a taxpayer may file a return, any such taxpayer who ceases to engage in the kind of business that makes the person responsible for filing returns under this Article shall file a final return under this Article with the Department within one month after discontinuing such business.
Each taxpayer under this Article shall make estimated payments to the Department on or before the 7th, 15th, 22nd, and last day of the month during which tax liability to the Department is incurred. The payments shall be in an amount not less than the lower of either 22.5% of the taxpayer's actual tax liability for the month or 25% of the taxpayer's actual tax liability for the same calendar month of the preceding year. The amount of the quarter-monthly payments shall be credited against the final tax liability of the taxpayer's return for that month. If any quarter-monthly payment is not paid at the time or in the amount required by this Section, then the taxpayer shall be liable for penalties and interest on the difference between the minimum amount due as a payment and the amount of the quarter-monthly payment actually and timely paid, except insofar as the taxpayer has previously made payments for that month to the Department in excess of the minimum payments previously due as provided in this Section.
If any payment provided for in this Section exceeds the taxpayer's liabilities under this Article, as shown on an original monthly return, the Department shall, if requested by the taxpayer, issue to the taxpayer a credit memorandum no later than 30 days after the date of payment. The credit evidenced by the credit memorandum may be assigned by the taxpayer to a similar taxpayer under this Act, in accordance with reasonable rules to be prescribed by the Department. If no such request is made, the taxpayer may credit the excess payment against tax liability subsequently to be remitted to the Department under this Act, in accordance with reasonable rules prescribed by the Department. If the Department subsequently determines that all or any part of the credit taken was not actually due to the taxpayer, the taxpayer's discount shall be reduced, if necessary, to reflect the difference between the credit taken and that actually due, and that taxpayer shall be liable for penalties and interest on the difference.
If a taxpayer fails to sign a return within 30 days after the proper notice and demand for signature by the Department is received by the taxpayer, the return shall be considered valid and any amount shown to be due on the return shall be deemed assessed.
410 ILCS 705/60-20