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taxes that average in excess of $20,000 per month during the preceding 4 complete calendar quarters shall file a return with the Department as required by Section 2f and shall make payments to the Department on or before the 7th, 15th, 22nd, and last day of the month during which the liability is incurred. Each payment shall be in an amount equal to 22.5% of the taxpayer's actual liability for the month or 25% of the taxpayer's 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 filed under this Section or Section 2f, as the case may be. Once applicable, the requirement of the making of quarter monthly payments to the Department pursuant to this paragraph shall continue until the taxpayer's average monthly prepaid tax collections during the preceding 4 complete calendar quarters (excluding the month of highest liability and the month of lowest liability) is less than $19,000 or until such taxpayer's average monthly liability to the Department as computed for each calendar quarter of the 4 preceding complete calendar quarters is less than $20,000. If any such quarter monthly payment is not paid at the time or in the amount required, the taxpayer shall be liable for penalties and interest on such difference, except insofar as the taxpayer has previously made payments for that month in excess of the minimum payments previously due. If any payment provided for in this Section exceeds the SB3019 Enrolled LRB104 20255 HLH 33706 b Public Act 104-0468