StructureCost2026

Quarterly estimated tax in Illinois (2026)

A sole proprietor in Illinois with $100,000 of profit pays the IRS about $5,032 a quarter, and owes $4,456 of Illinois income tax for the year. Put in your own profit to get the four payments and their dates.

$5,032 a quarter

to the IRS. Four payments make $20,128 for the year, which meets 90% of this year's tax. This year's federal tax on this profit: $22,365 (income tax $8,235, self-employment tax $14,130).

Illinois, 2026: $100,000 profit, single filer

IRS dueIncome earnedIRSIllinois dueIllinois
April 15, 2026January 1 to March 31$5,032April 15, 2026$1,003
June 15, 2026April 1 to May 31$5,032June 15, 2026$1,003
September 15, 2026June 1 to August 31$5,032September 15, 2026$1,003
January 15, 2027September 1 to December 31$5,032January 15, 2027$1,003
Year$20,128$4,012

Illinois payments cover 90% of this year's state tax of $4,456, split 25%, 25%, 25%, 25% (Form IL-1040-ES). tax.illinois.gov, checked Oct 24, 2026 Estimates assume a single-member business with no withholding.

Illinois estimated tax rules for 2026

Payments at each profit

ProfitIRS each quarterIllinois for the year
$50,000$2,190$1,940
$100,000$5,032$4,010
$150,000$8,462$6,080
$250,000$14,931$10,348
$500,000$37,744$21,337

A sole proprietor or single-member LLC, single filer, no withholding, paying 90% of this year's federal tax and the state's own safe-harbor share.

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