Form 40: Idaho Individual Income Tax Return

Form 40 is the official document used by Idaho residents to file their individual income tax return with the Idaho State Tax Commission (STC) for tax year 2023 (income earned between January 1st and December 31st, 2023).

Who Needs to File Form 40?

  • Generally, all Idaho residents with taxable income exceeding the federal filing threshold are required to file Form 40.
  • Part-year residents and non-residents with income sourced from Idaho may need to file using Form 40/43.

What's Included In Form 40?

  • Filing Status: Select your filing status (Single, Married Filing Jointly, etc.)
  • Exemptions: Claim exemptions for yourself, spouse, and dependents.
  • Income: Report all taxable income earned in Idaho (wages, interest, dividends, etc.)
  • Deductions: Itemize deductions or take the standard deduction.
  • Credits: Claim any applicable tax credits.
  • Tax Calculation: Calculate your total tax liability based on Idaho tax brackets.
  • Payments & Refunds: Report any tax withheld from your income and determine if you owe additional tax or are due a refund.

How to File Form 40?

Electronically: Idaho offers free e-filing through its website (

Paper Form: Download the form and instructions attached below. Mail the completed form with any required attachments to the Idaho State Tax Commission.