Illinois State Income Tax Calculator

Quickly estimate your Illinois state income tax using a flat-rate model with exemptions and pre-tax adjustments. Built for employees, contractors, and planners who want a fast, accurate, and transparent calculation with professional, WCAG-compliant UX.

Calculator

Choose the filing status you expect on your IL-1040.

$
Enter your total annual wages/salary before taxes. For hourly work, multiply your hourly rate by expected hours for the year.
$
Enter total annual pre-tax deductions that reduce federal wages and typically flow into Illinois taxable income (e.g., 401k, HSA, FSA). Do not include post-tax amounts.
$
Certain income may be added back for Illinois purposes (e.g., interest from other states’ municipal bonds). See IDOR guidance for details.
$
Illinois allows certain subtractions (e.g., some retirement income). Enter the total you expect to subtract from Illinois income.
Illinois provides a personal exemption for you and, if filing jointly, for your spouse. Enter how many personal exemptions apply. Amount varies by tax year and may be subject to phase-outs.
Enter the number of dependents you can claim. Illinois provides an additional dependent exemption that can reduce taxable income.
$
Default set to a common recent-year value. Always confirm the current-year amount with IDOR, as it may change and can phase out at higher incomes.
$
Default set to a common recent-year value. Verify the current-year dependent exemption with IDOR.
%
Illinois uses a flat income tax rate (4.95% since 2017). Enter another value if the rate changes for your tax year.

This tool provides educational estimates and is not tax or legal advice.

Results

Taxable Illinois Income
$0.00
Illinois State Income Tax
$0.00
Effective State Tax Rate
0.00%
Estimated Net After State Tax
$0.00
Monthly State Tax
$0.00
Biweekly State Tax
$0.00
Weekly State Tax
$0.00
Enter your income and details to see results.

Data Source and Methodology

Authoritative source: Illinois Department of Revenue (IDOR) — Individual Income Tax (IL-1040) Instructions and Rate Guidance. See: https://tax.illinois.gov/ and IL-1040 Instructions for your tax year.

All calculations implement the Illinois flat-rate model as publicly documented (rate 4.95% since 2017), with adjustments for Illinois additions/subtractions and exemptions. Exemption amounts can change and may be subject to income phase-outs; always verify the current-year figures in the official IL-1040 instructions.

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

$$\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)$$ $$\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)$$ $$\text{Illinois Tax} = \text{Taxable Income} \times r$$ $$\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}$$ $$\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}$$ Where: $$W=\text{Annual wages},\; P=\text{Pre-tax contrib.},\; A=\text{IL additions},\; S=\text{IL subtractions},\; r=\text{rate}.$$ $$E_p=\text{personal exemptions count},\; A_p=\text{per-person personal amount},\; E_d=\text{dependents count},\; A_d=\text{per-dependent amount}.$$

Glossary of Variables

Worked Example

How It Works: A Step-by-Step Example

Suppose you earn W = $80,000, contribute P = $6,000 pre-tax, have no Illinois additions (A = $0) and no subtractions (S = $0). You file Single with one personal exemption (E_p = 1) at A_p = $2,425 and no dependents (E_d = 0).

ExemptionsTotal = (1 × 2,425) + (0 × A_d) = 2,425 Taxable Income = max(0, 80,000 − 6,000 + 0 − 0 − 2,425) = 71,575 Illinois Tax = 71,575 × 0.0495 = 3,542.96 Effective Rate = 3,542.96 / 80,000 = 4.43% Monthly Tax ≈ 3,542.96 / 12 = 295.25

Numbers are rounded for readability. This example ignores any phase-outs or year-specific changes; always confirm current-year exemption amounts.

Frequently Asked Questions (FAQ)

Is Illinois a flat tax state?

Yes. Illinois uses a flat state income tax rate applied to taxable income after adjustments and exemptions.

What is included in taxable Illinois income?

Illinois generally starts from federal AGI and applies state-specific additions, subtractions, and exemptions. Use the Additions/Subtractions fields to approximate your situation.

Does this tool include federal withholding or payroll taxes?

No. It only estimates Illinois state income tax. Federal income tax and FICA (Social Security and Medicare) are not included.

Can I account for personal and dependent exemptions?

Yes. Enter the counts and per-person amounts. The defaults reflect common recent-year values, but you should confirm your tax year’s official amounts with IDOR.

Are local income taxes added on top of the Illinois rate?

No. Illinois does not impose local income taxes.

Will this match my paycheck exactly?

Likely not. Employers use withholding formulas and payroll timing. This calculator provides a yearly estimate for planning.

Is my data stored?

No. All computations run in your browser. You can share your current inputs using the Share button, which encodes values in the URL.

Authorship and Review

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\]
','
Formula (extracted LaTeX)
\[\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)\]
\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)
Formula (extracted LaTeX)
\[\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)\]
\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)
Formula (extracted LaTeX)
\[\text{Illinois Tax} = \text{Taxable Income} \times r\]
\text{Illinois Tax} = \text{Taxable Income} \times r
Formula (extracted LaTeX)
\[\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}\]
\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}
Formula (extracted LaTeX)
\[\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}\]
\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}
Formula (extracted text)
$\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)$ $\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)$ $\text{Illinois Tax} = \text{Taxable Income} \times r$ $\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}$ $\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}$ Where: $W=\text{Annual wages},\; P=\text{Pre-tax contrib.},\; A=\text{IL additions},\; S=\text{IL subtractions},\; r=\text{rate}.$ $E_p=\text{personal exemptions count},\; A_p=\text{per-person personal amount},\; E_d=\text{dependents count},\; A_d=\text{per-dependent amount}.$
Formula (extracted text)
ExemptionsTotal = (1 × 2,425) + (0 × A_d) = 2,425 Taxable Income = max(0, 80,000 − 6,000 + 0 − 0 − 2,425) = 71,575 Illinois Tax = 71,575 × 0.0495 = 3,542.96 Effective Rate = 3,542.96 / 80,000 = 4.43% Monthly Tax ≈ 3,542.96 / 12 = 295.25
Variables and units
  • T = property tax (annual or monthly depending on input) (currency)
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn
, ', svg: { fontCache: 'global' } };

Illinois State Income Tax Calculator

Quickly estimate your Illinois state income tax using a flat-rate model with exemptions and pre-tax adjustments. Built for employees, contractors, and planners who want a fast, accurate, and transparent calculation with professional, WCAG-compliant UX.

Calculator

Choose the filing status you expect on your IL-1040.

$
Enter your total annual wages/salary before taxes. For hourly work, multiply your hourly rate by expected hours for the year.
$
Enter total annual pre-tax deductions that reduce federal wages and typically flow into Illinois taxable income (e.g., 401k, HSA, FSA). Do not include post-tax amounts.
$
Certain income may be added back for Illinois purposes (e.g., interest from other states’ municipal bonds). See IDOR guidance for details.
$
Illinois allows certain subtractions (e.g., some retirement income). Enter the total you expect to subtract from Illinois income.
Illinois provides a personal exemption for you and, if filing jointly, for your spouse. Enter how many personal exemptions apply. Amount varies by tax year and may be subject to phase-outs.
Enter the number of dependents you can claim. Illinois provides an additional dependent exemption that can reduce taxable income.
$
Default set to a common recent-year value. Always confirm the current-year amount with IDOR, as it may change and can phase out at higher incomes.
$
Default set to a common recent-year value. Verify the current-year dependent exemption with IDOR.
%
Illinois uses a flat income tax rate (4.95% since 2017). Enter another value if the rate changes for your tax year.

This tool provides educational estimates and is not tax or legal advice.

Results

Taxable Illinois Income
$0.00
Illinois State Income Tax
$0.00
Effective State Tax Rate
0.00%
Estimated Net After State Tax
$0.00
Monthly State Tax
$0.00
Biweekly State Tax
$0.00
Weekly State Tax
$0.00
Enter your income and details to see results.

Data Source and Methodology

Authoritative source: Illinois Department of Revenue (IDOR) — Individual Income Tax (IL-1040) Instructions and Rate Guidance. See: https://tax.illinois.gov/ and IL-1040 Instructions for your tax year.

All calculations implement the Illinois flat-rate model as publicly documented (rate 4.95% since 2017), with adjustments for Illinois additions/subtractions and exemptions. Exemption amounts can change and may be subject to income phase-outs; always verify the current-year figures in the official IL-1040 instructions.

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

$$\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)$$ $$\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)$$ $$\text{Illinois Tax} = \text{Taxable Income} \times r$$ $$\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}$$ $$\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}$$ Where: $$W=\text{Annual wages},\; P=\text{Pre-tax contrib.},\; A=\text{IL additions},\; S=\text{IL subtractions},\; r=\text{rate}.$$ $$E_p=\text{personal exemptions count},\; A_p=\text{per-person personal amount},\; E_d=\text{dependents count},\; A_d=\text{per-dependent amount}.$$

Glossary of Variables

Worked Example

How It Works: A Step-by-Step Example

Suppose you earn W = $80,000, contribute P = $6,000 pre-tax, have no Illinois additions (A = $0) and no subtractions (S = $0). You file Single with one personal exemption (E_p = 1) at A_p = $2,425 and no dependents (E_d = 0).

ExemptionsTotal = (1 × 2,425) + (0 × A_d) = 2,425 Taxable Income = max(0, 80,000 − 6,000 + 0 − 0 − 2,425) = 71,575 Illinois Tax = 71,575 × 0.0495 = 3,542.96 Effective Rate = 3,542.96 / 80,000 = 4.43% Monthly Tax ≈ 3,542.96 / 12 = 295.25

Numbers are rounded for readability. This example ignores any phase-outs or year-specific changes; always confirm current-year exemption amounts.

Frequently Asked Questions (FAQ)

Is Illinois a flat tax state?

Yes. Illinois uses a flat state income tax rate applied to taxable income after adjustments and exemptions.

What is included in taxable Illinois income?

Illinois generally starts from federal AGI and applies state-specific additions, subtractions, and exemptions. Use the Additions/Subtractions fields to approximate your situation.

Does this tool include federal withholding or payroll taxes?

No. It only estimates Illinois state income tax. Federal income tax and FICA (Social Security and Medicare) are not included.

Can I account for personal and dependent exemptions?

Yes. Enter the counts and per-person amounts. The defaults reflect common recent-year values, but you should confirm your tax year’s official amounts with IDOR.

Are local income taxes added on top of the Illinois rate?

No. Illinois does not impose local income taxes.

Will this match my paycheck exactly?

Likely not. Employers use withholding formulas and payroll timing. This calculator provides a yearly estimate for planning.

Is my data stored?

No. All computations run in your browser. You can share your current inputs using the Share button, which encodes values in the URL.

Authorship and Review

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\]
','
Formula (extracted LaTeX)
\[\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)\]
\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)
Formula (extracted LaTeX)
\[\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)\]
\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)
Formula (extracted LaTeX)
\[\text{Illinois Tax} = \text{Taxable Income} \times r\]
\text{Illinois Tax} = \text{Taxable Income} \times r
Formula (extracted LaTeX)
\[\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}\]
\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}
Formula (extracted LaTeX)
\[\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}\]
\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}
Formula (extracted text)
$\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)$ $\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)$ $\text{Illinois Tax} = \text{Taxable Income} \times r$ $\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}$ $\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}$ Where: $W=\text{Annual wages},\; P=\text{Pre-tax contrib.},\; A=\text{IL additions},\; S=\text{IL subtractions},\; r=\text{rate}.$ $E_p=\text{personal exemptions count},\; A_p=\text{per-person personal amount},\; E_d=\text{dependents count},\; A_d=\text{per-dependent amount}.$
Formula (extracted text)
ExemptionsTotal = (1 × 2,425) + (0 × A_d) = 2,425 Taxable Income = max(0, 80,000 − 6,000 + 0 − 0 − 2,425) = 71,575 Illinois Tax = 71,575 × 0.0495 = 3,542.96 Effective Rate = 3,542.96 / 80,000 = 4.43% Monthly Tax ≈ 3,542.96 / 12 = 295.25
Variables and units
  • T = property tax (annual or monthly depending on input) (currency)
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn
]], displayMath: [['\\[','\\]']] }, svg: { fontCache: 'global' } };, svg: { fontCache: 'global' } };

Illinois State Income Tax Calculator

Quickly estimate your Illinois state income tax using a flat-rate model with exemptions and pre-tax adjustments. Built for employees, contractors, and planners who want a fast, accurate, and transparent calculation with professional, WCAG-compliant UX.

Calculator

Choose the filing status you expect on your IL-1040.

$
Enter your total annual wages/salary before taxes. For hourly work, multiply your hourly rate by expected hours for the year.
$
Enter total annual pre-tax deductions that reduce federal wages and typically flow into Illinois taxable income (e.g., 401k, HSA, FSA). Do not include post-tax amounts.
$
Certain income may be added back for Illinois purposes (e.g., interest from other states’ municipal bonds). See IDOR guidance for details.
$
Illinois allows certain subtractions (e.g., some retirement income). Enter the total you expect to subtract from Illinois income.
Illinois provides a personal exemption for you and, if filing jointly, for your spouse. Enter how many personal exemptions apply. Amount varies by tax year and may be subject to phase-outs.
Enter the number of dependents you can claim. Illinois provides an additional dependent exemption that can reduce taxable income.
$
Default set to a common recent-year value. Always confirm the current-year amount with IDOR, as it may change and can phase out at higher incomes.
$
Default set to a common recent-year value. Verify the current-year dependent exemption with IDOR.
%
Illinois uses a flat income tax rate (4.95% since 2017). Enter another value if the rate changes for your tax year.

This tool provides educational estimates and is not tax or legal advice.

Results

Taxable Illinois Income
$0.00
Illinois State Income Tax
$0.00
Effective State Tax Rate
0.00%
Estimated Net After State Tax
$0.00
Monthly State Tax
$0.00
Biweekly State Tax
$0.00
Weekly State Tax
$0.00
Enter your income and details to see results.

Data Source and Methodology

Authoritative source: Illinois Department of Revenue (IDOR) — Individual Income Tax (IL-1040) Instructions and Rate Guidance. See: https://tax.illinois.gov/ and IL-1040 Instructions for your tax year.

All calculations implement the Illinois flat-rate model as publicly documented (rate 4.95% since 2017), with adjustments for Illinois additions/subtractions and exemptions. Exemption amounts can change and may be subject to income phase-outs; always verify the current-year figures in the official IL-1040 instructions.

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

$$\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)$$ $$\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)$$ $$\text{Illinois Tax} = \text{Taxable Income} \times r$$ $$\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}$$ $$\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}$$ Where: $$W=\text{Annual wages},\; P=\text{Pre-tax contrib.},\; A=\text{IL additions},\; S=\text{IL subtractions},\; r=\text{rate}.$$ $$E_p=\text{personal exemptions count},\; A_p=\text{per-person personal amount},\; E_d=\text{dependents count},\; A_d=\text{per-dependent amount}.$$

Glossary of Variables

Worked Example

How It Works: A Step-by-Step Example

Suppose you earn W = $80,000, contribute P = $6,000 pre-tax, have no Illinois additions (A = $0) and no subtractions (S = $0). You file Single with one personal exemption (E_p = 1) at A_p = $2,425 and no dependents (E_d = 0).

ExemptionsTotal = (1 × 2,425) + (0 × A_d) = 2,425 Taxable Income = max(0, 80,000 − 6,000 + 0 − 0 − 2,425) = 71,575 Illinois Tax = 71,575 × 0.0495 = 3,542.96 Effective Rate = 3,542.96 / 80,000 = 4.43% Monthly Tax ≈ 3,542.96 / 12 = 295.25

Numbers are rounded for readability. This example ignores any phase-outs or year-specific changes; always confirm current-year exemption amounts.

Frequently Asked Questions (FAQ)

Is Illinois a flat tax state?

Yes. Illinois uses a flat state income tax rate applied to taxable income after adjustments and exemptions.

What is included in taxable Illinois income?

Illinois generally starts from federal AGI and applies state-specific additions, subtractions, and exemptions. Use the Additions/Subtractions fields to approximate your situation.

Does this tool include federal withholding or payroll taxes?

No. It only estimates Illinois state income tax. Federal income tax and FICA (Social Security and Medicare) are not included.

Can I account for personal and dependent exemptions?

Yes. Enter the counts and per-person amounts. The defaults reflect common recent-year values, but you should confirm your tax year’s official amounts with IDOR.

Are local income taxes added on top of the Illinois rate?

No. Illinois does not impose local income taxes.

Will this match my paycheck exactly?

Likely not. Employers use withholding formulas and payroll timing. This calculator provides a yearly estimate for planning.

Is my data stored?

No. All computations run in your browser. You can share your current inputs using the Share button, which encodes values in the URL.

Authorship and Review

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[','\]
','
Formula (extracted LaTeX)
\[\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)\]
\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)
Formula (extracted LaTeX)
\[\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)\]
\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)
Formula (extracted LaTeX)
\[\text{Illinois Tax} = \text{Taxable Income} \times r\]
\text{Illinois Tax} = \text{Taxable Income} \times r
Formula (extracted LaTeX)
\[\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}\]
\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}
Formula (extracted LaTeX)
\[\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}\]
\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}
Formula (extracted text)
$\text{ExemptionsTotal} = (E_p \times A_p) + (E_d \times A_d)$ $\text{Taxable Income} = \max\big(0,\; W - P + A - S - \text{ExemptionsTotal}\big)$ $\text{Illinois Tax} = \text{Taxable Income} \times r$ $\text{Effective Rate} = \begin{cases} 0 & \text{if } W = 0 \\ \dfrac{\text{Illinois Tax}}{W} & \text{if } W > 0 \end{cases}$ $\text{Periodic Tax} = \left\{\frac{\text{Tax}}{12},\;\frac{\text{Tax}}{26},\;\frac{\text{Tax}}{52}\right\}\;\;\text{(monthly, biweekly, weekly)}$ Where: $W=\text{Annual wages},\; P=\text{Pre-tax contrib.},\; A=\text{IL additions},\; S=\text{IL subtractions},\; r=\text{rate}.$ $E_p=\text{personal exemptions count},\; A_p=\text{per-person personal amount},\; E_d=\text{dependents count},\; A_d=\text{per-dependent amount}.$
Formula (extracted text)
ExemptionsTotal = (1 × 2,425) + (0 × A_d) = 2,425 Taxable Income = max(0, 80,000 − 6,000 + 0 − 0 − 2,425) = 71,575 Illinois Tax = 71,575 × 0.0495 = 3,542.96 Effective Rate = 3,542.96 / 80,000 = 4.43% Monthly Tax ≈ 3,542.96 / 12 = 295.25
Variables and units
  • T = property tax (annual or monthly depending on input) (currency)
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn