Authoritative Data & Methodology
Primary Data Sources
- Indiana Department of Revenue — Tax Rates and County Income Tax Rates by Year (last accessed: 2025-09-13). Direct links: State and Local Tax Rates, County Income Tax Rates by Year.
- Indiana IT-40 Individual Income Tax Instructions (for definitions of taxable income and county tax applicability). in.gov/dor
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.
This calculator applies Indiana’s flat state rate and the user-provided county income tax rate to the entered Indiana taxable income.
The Formula Explained
State tax:
\[ T_s = I \times r_s \]
County tax (resident):
\[ T_c = I \times r_{c}^{res} \]
County tax (nonresident working in IN):
\[ T_c = I \times r_{c}^{emp} \]
Total Indiana tax:
\[ T = T_s + T_c \]
After-tax income:
\[ N = I - T \]
Effective Indiana tax rate:
\[ e = \frac{T}{I} \times 100\% \]
Glossary of Variables
- I — Indiana taxable income (annual, USD) you enter.
- r_s — Indiana flat state rate (percent ÷ 100), defaulted by year.
- r_c^{res} — County income tax rate for county of residence (percent ÷ 100).
- r_c^{emp} — County income tax rate for county of principal employment (for nonresidents who work in Indiana).
- T_s — Indiana state income tax amount (USD).
- T_c — Indiana county income tax amount (USD).
- T — Total Indiana income tax (USD), state + county.
- N — After-tax income (USD) = I − T.
- e — Effective Indiana tax rate as a percentage.
How It Works: A Step-by-Step Example
- Assume Indiana taxable income I = $75,000.
- Tax year 2024 with state rate r_s = 3.05% → 0.0305.
- Resident of Marion County with county rate r_c^{res} = 1.75% → 0.0175.
- Compute state tax: T_s = 75,000 × 0.0305 = $2,287.50.
- Compute county tax: T_c = 75,000 × 0.0175 = $1,312.50.
- Total Indiana tax: T = 2,287.50 + 1,312.50 = $3,600.00.
- After-tax income: N = 75,000 − 3,600 = $71,400.00.
- Effective rate: e = (3,600 / 75,000) × 100% = 4.80%.
This example excludes other credits, withholdings, or local nuances. Always follow the latest DOR instructions when filing.
Frequently Asked Questions (FAQ)
What is the Indiana state income tax rate?
Indiana uses a flat state income tax rate that can change by year. The calculator loads a default rate for the selected year, but you should always verify the current rate at the Indiana Department of Revenue.
How do I find my county income tax rate?
Use the official DOR table: County Income Tax Rates by Year. Find your county (residence or principal employment) and enter the correct percentage.
Does this tool calculate payroll withholding?
It estimates annual liabilities using flat rates. Payroll withholding can vary based on withholding forms and employer practices. For paycheck-level estimates, divide the annual amounts by your pay frequency.
What income should I enter?
Enter your Indiana taxable income. If you only know your federal AGI, subtract Indiana-specific deductions and exemptions to approximate your Indiana taxable income.
How are nonresidents treated?
Nonresidents who work in Indiana may owe county tax to the county of principal employment. If you neither live nor work in Indiana, county tax is typically zero.
Will credits or other adjustments change my results?
Yes. Credits (e.g., other state tax credits) and additional adjustments can reduce your actual tax due. This calculator focuses on the base computation of state and county taxes.