How this calculator works
Tax year: 2024 for the Alabama, California, Illinois and New York rate presets. All other states require you to supply their official brackets for your chosen year and filing status. This makes the worksheet usable without inventing unverified state rates. The starting amount must already reflect state deductions and exemptions. California's mental-health supplement and New York high-income recapture are included in their presets. Custom schedules cannot model recapture, local taxes, credits or special income treatments.
Formula
State tax = sum of taxable income in each band x its rate, plus preset supplements when applicable. A flat rate is a single row with upper limit * and the official percentage rate. Deductions must already be removed.
Worked example
At $10,000 taxable income and $10,000 AGI, the 2024 single Alabama preset gives $460 and Illinois gives $495 before credits. A custom row with upper limit * and rate 5% on $10,000 gives $500.
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Frequently asked questions
Are all state rates built in?
No. Only four 2024 presets are built in. Other states require an official rate schedule that you enter explicitly.
How do I represent no state tax on the income?
If the official rules establish that this income is untaxed, enter one custom row with upper limit * and rate 0%.
Does choosing a state apply its deductions?
No. Enter state taxable income after all applicable deductions and exemptions; use a dedicated state page to build it from AGI.