Illinois has a flat income tax system, meaning a single tax rate applies to all taxable income, regardless of how much you earn. This contrasts with progressive tax systems where higher earners pay a higher percentage of their income in taxes. As of the latest tax years, Illinois maintains this flat rate structure.
Key Components of Illinois Income Tax:
Flat Tax Rate: Illinois applies a single percentage to your taxable income. This rate can change based on state legislation. For recent years, this rate has been 4.95%.
Taxable Income: This is not your gross income. It's calculated by taking your Adjusted Gross Income (AGI) and subtracting any allowable deductions and exemptions.
Deductions & Exemptions: Illinois offers various deductions and exemptions that can reduce your taxable income. These can include personal exemptions (often a fixed amount per taxpayer and dependent) and specific deductions for certain expenses. For simplicity in this calculator, we've combined these into a single "Deductions & Exemptions" field.
How the Illinois Taxes Calculator Works:
This calculator estimates your Illinois state income tax liability based on the information you provide. The process is as follows:
Input Income: Enter your total annual income before any deductions.
Input Deductions: Enter the total amount of deductions and exemptions you are eligible for. This might include personal exemptions, dependency exemptions, and any other specific deductions allowed by Illinois law.
Calculate Taxable Income: The calculator subtracts your total deductions and exemptions from your annual income to determine your taxable income:
Taxable Income = Annual Income - Deductions & Exemptions
Apply Tax Rate: The Illinois flat tax rate is applied to the calculated taxable income. For the years covered by this calculator (2023 and 2024), the state has maintained a flat rate of 4.95%.
Estimated Illinois Income Tax = Taxable Income * Tax Rate (4.95%)
Example: If your Annual Income is $75,000 and your Deductions & Exemptions total $4,000:
Taxable Income = $75,000 – $4,000 = $71,000
Estimated Illinois Income Tax = $71,000 * 0.0495 = $3,514.50
Important Considerations:
This calculator provides an estimate for Illinois state income tax only and does not include federal taxes or other local taxes.
Tax laws and rates are subject to change. Consult with a qualified tax professional or refer to the official Illinois Department of Revenue (IDOR) for the most current and accurate tax information.
The specific deductions and exemptions available can be complex. This calculator uses a simplified input for your convenience.
function calculateIllinoisTaxes() {
var income = parseFloat(document.getElementById("income").value);
var deductions = parseFloat(document.getElementById("deductions").value);
var taxYear = document.getElementById("tax_year").value;
var calculatedTax = 0;
var taxRate = 0;
// Define tax rates based on tax year. For simplicity, using 4.95% for both 2023 and 2024.
// This rate can change, so it's important to verify with official sources.
if (taxYear === "2023" || taxYear === "2024") {
taxRate = 0.0495; // 4.95%
} else {
// Fallback or error for unsupported years, though we only have 2023/2024 options
document.getElementById("result-value").innerText = "N/A";
return;
}
// Validate inputs
if (isNaN(income) || isNaN(deductions) || income < 0 || deductions < 0) {
document.getElementById("result-value").innerText = "Invalid Input";
return;
}
var taxableIncome = income – deductions;
// Ensure taxable income is not negative
if (taxableIncome < 0) {
taxableIncome = 0;
}
calculatedTax = taxableIncome * taxRate;
// Format the result to two decimal places for currency
var formattedTax = calculatedTax.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
document.getElementById("result-value").innerText = formattedTax;
}