Illinois tax guide

Illinois taxes for self-employed workers in 2026

Illinois has one flat income tax rate and four equal payments, which makes it one of the simpler states to plan for. Here's what you need for 2026.

Published by Cadus Labs LLC · Last updated November 9, 2026 · How we write these guides

Based on Illinois Department of Revenue Publication 105 and the 2026 Form IL-1040-ES.

Illinois estimated tax payments for 2026

The Illinois individual income tax rate is a flat 4.95%. You have to make estimated payments if you reasonably expect your tax for the year to exceed $1,000 after Illinois withholding and certain credits.

The form is Form IL-1040-ES, and you can generally pay online instead of mailing it.

2026 Illinois estimated tax payment dates for calendar-year filers
Payment due	Share of the year's required payment
April 15, 2026	25%
June 15, 2026	25%
September 15, 2026	25%
January 15, 2027	25%

You can also pay the whole year's estimate on April 15, 2026 instead of in four installments.

A simple way to plan

A flat rate makes the arithmetic easy: estimate your Illinois taxable income for the year and multiply by 4.95%. If that's more than $1,000 after withholding and credits, divide by four and put each payment on your calendar.

Your federal tax comes first

Wherever you live, self-employed income is subject to federal income tax and self-employment tax. A single filer with $60,000 of net profit and no other income owes about $12,037 in federal tax for 2026, or 20% of profit, before any state or local tax.

Federal estimated payments are due April 15, June 15, and September 15, 2026, and January 15, 2027. Use our 1099 tax calculator to run your own numbers.

Recordkeeping checklist

Set aside for federal and state tax from every payment you receive.

Make federal and state estimated payments if you expect to owe enough.

Keep receipts and a mileage log for everything you deduct.

Put all four Illinois payment dates on your calendar.

Free tools for this

Calculator

1099 and Self-Employment Tax Calculator

Enter your 1099 income and business expenses to estimate self-employment tax, federal income tax, and what to set aside each quarter. No sign-up, and nothing you type is saved.

Calculator

Quarterly Tax Set-Aside Calculator

Turn expected profit into a practical tax savings target, then use Cadus to keep income, expenses, deductions, receipts, and reports organized.

Template

Quarterly Tax Savings Worksheet

Use this worksheet to turn expected monthly profit into a practical tax savings target before estimated tax due dates arrive.

Template

Business Expense Log Template

Copy this table to start organizing business purchases, receipt proof, categories, and business purpose before moving records into Cadus.

Official sources

Illinois DOR: Publication 105 Illinois DOR: Form IL-1040-ES

Related guides

Self-employment tax guide

Self-Employment Tax

The self-employment tax rate is 15.3%. See who pays, how the 2026 wage base works, the deduction for half the tax, and a worked example.

Estimated tax guide

Quarterly Estimated Taxes

2026 estimated tax due dates, who has to pay, how to avoid the penalty, and a worked example for a self-employed worker earning $60,000.

Schedule C education

Schedule C Expense Categories

Every Schedule C expense line in plain English: what goes on each one, what doesn't, and the records to keep for self-employed workers.

Illinois Taxes FAQ

What is the Illinois income tax rate for self-employed people?

A flat 4.95%.

When do I have to pay Illinois estimated tax?

When you reasonably expect your tax for the year to exceed $1,000 after Illinois withholding and certain credits.

Cadus educational content is not tax, legal, or accounting advice. Tax rules can change, and individual facts matter. Review official guidance or speak with a qualified tax professional before filing.