Idaho State Tax Forms

Idaho offers a comprehensive set of tax forms for individuals and businesses, all administered by the Idaho State Tax Commission (ISTC).

These forms are used to report income, calculate tax liability, claim deductions and credits, and remit payments to the state.

Selecting the correct form depends on your residency status, income sources, and whether you are filing as an individual or a business entity.

Key Idaho Individual Income Tax Forms

Form 40 – Idaho Individual Income Tax Return

This is the primary income tax return for full-year Idaho residents. It is used to report all taxable income, claim deductions and credits, and determine whether additional tax is owed or a refund is due.

Form 43 – Idaho Part-Year Resident & Nonresident Income Tax Return

This form is required for individuals who lived in Idaho for only part of the year or who were nonresidents with Idaho-source income. It allocates income between Idaho and other states.

Form 39R – Idaho Resident Supplemental Schedule

Used by full-year residents to report additional information such as:

• Credits for income taxes paid to another state
• Additional dependents not listed on the main return
• Other supplemental adjustments

Form 39NR – Idaho Part-Year Resident & Nonresident Supplemental Schedule

This schedule supports Form 43 and serves the same purpose as Form 39R but is specifically for part-year residents and nonresidents.

Form CG – Idaho Capital Gains Deduction

Allows eligible taxpayers to claim a deduction for qualifying Idaho capital gains, subject to specific holding periods and eligibility requirements.

Form 51 – Estimated Payment of Idaho Individual Income Tax

Used to submit quarterly estimated tax payments if you are self-employed, receive non-wage income, or do not have sufficient withholding.

Form ID W-4 – Employee’s Withholding Allowance Certificate

Employees use this form to instruct their employer on how much Idaho income tax to withhold from each paycheck.

Form 40X – Amended Idaho Individual Income Tax Return

Filed to correct errors or make changes to a previously submitted Idaho income tax return, such as income adjustments, filing status changes, or missed credits.

Key Idaho Business Tax Forms

Idaho businesses must file additional forms depending on their entity type and activities within the state:

Form 41 – Idaho Corporation Income Tax Return

For C corporations conducting business in Idaho.

Form 41S – Idaho S Corporation Income Tax Return

Used by S corporations to report Idaho-source income and pass-through items.

Form 65 – Idaho Partnership Return of Income

Required for partnerships and LLCs taxed as partnerships that have Idaho income or operations.

Form 850 – Sales and Use Tax Return

Used by businesses to report and remit sales and use tax, including retail sales, rentals, and taxable services.

Recommendation: File Electronically

The Idaho State Tax Commission encourages taxpayers to file electronically whenever possible. E-filing offers several advantages:

• Faster processing and quicker refunds
• Built-in error checks that reduce mistakes
• Secure electronic submission and payment options
• Immediate confirmation that your return was received
• Easy access to prior-year filings and records

Most major tax preparation software supports Idaho e-filing, and businesses can also file and pay through the ISTC’s online systems.

Where to Find Idaho Tax Forms

Current and archived Idaho tax forms, instructions, and e-filing resources are available on the official Idaho State Tax Commission website, ensuring you always have access to the most up-to-date and accurate information.