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//// Tax · Illinois

Illinois 1099 Quarterly Tax

SE income → SE tax + federal + IL 4.95% flat tax → quarterly estimated payment.

Where this fits

🧾 TaxTax StackGoing 1099Freelancers

This tool lives inside Tax Stack + Going 1099 and is most useful for freelancers.

401(k) Limit 2024$23,000
Roth IRA Limit$7,000
S&P 500 Avg Return~10%/yr

Income

Quarterly payment
$4,733
estimated
Annual tax
$18,933
SE + federal + state
Safe harbor
$3,375
prior year ÷ 4
Effective rate
26.7%
of net SE income

Tax breakdown

Self-employment tax$10,032
Federal income tax$6,357
Illinois state tax$2,544
Total annual$18,933
Per quarter$4,733
Per month (set aside)$1,578
1

Net self-employment income

netSE = gross − expenses

= $88,000 − $17,000

= $71,000

2

Self-employment tax (Schedule SE)

SE base = netSE × 92.35%; SE tax = base × 15.3%

= $10,032

SE tax = Social Security (12.4%) + Medicare (2.9%)

3

Adjusted gross income

AGI = netSE − (SE tax × 50%)

= $71,000 − $5,016

= $65,984

The 50% SE deduction compensates for the employer half of FICA

4

Federal income tax

federal = brackets(AGI − standard deduction)

= brackets($65,984 − $14,600)

= $6,357

Taxable income: $51,384 · Standard deduction: $14,600

5

Illinois state tax

= $2,544

Illinois has a flat 4.95% state income tax.

6

Quarterly payment

quarterly = totalAnnualTax ÷ 4

= $18,933 ÷ 4

= $4,733

IRS Form 1040-ES due: April 15, June 15, September 15, January 15

Key insight

Illinois has a flat 4.95% state income tax. Pay quarterly by: April 15 (Q1), June 15 (Q2), September 15 (Q3), January 15 (Q4). Underpaying triggers a penalty (~8% annualized on the shortfall). When in doubt, pay the safe harbor amount.

Use this result in →

📅Quarterly Tax Calculator💸Self-Employment Tax

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