402: Individual Apportionment for Multistate Businesses (Revision)
Idaho · Idaho Tax Commission · Used for tax years 2024, 2025, 2026
Idaho Form 402 calculates the Idaho apportionment factor for an individual's multistate business income. It reports total and Idaho property, gross receipts, and payroll to determine the portion of multistate business income or loss reported on Idaho Form 43.
Who files this form
Form 402 covers Idaho apportionment for a nonresident who conducts business in Idaho and another state or country. The instructions state that your entire business income is subject to Idaho apportionment.
All taxpayers completing this form must fill out the property, sales, and payroll sections, even if they use only the sales factor to calculate their Idaho apportionment factor.
What you'll need
Have the following information available to complete Form 402:
- Names as shown on your return, your Social Security number or EIN, and your calendar or fiscal tax year.
- Total and Idaho property amounts at the beginning and end of the year, at original cost, plus net annual rents.
- Total and Idaho sales and other gross receipts, including relevant gross sales from Form 4797 and/or Schedule D.
- Total and Idaho wages, salaries, and other employee compensation.
- Net income or loss from multistate activities reported on Schedules C, E, and F. The instructions direct you to apply the apportionment factor to these amounts and enter the results on Idaho Form 43.
If you use three-factor apportionment, provide a list of the companies using that method.
Common mistakes
- Skipping sections when using the single sales factor. All taxpayers must complete the property, payroll, and sales sections. Only three-factor taxpayers use all three factors in the calculation.
- Forgetting to identify three-factor use. If you use that method, check the box and provide a list of the companies using it.
- Including inventoriable goods in process on line 8. The instructions specifically say not to include them there.
- Using a different long-term contract accounting method for Idaho. Contractors must use the same method they used for federal reporting.
- Including construction-project equity when progress billings exceed construction costs. Under the contractor percentage-of-completion rules, do not include that equity in the property factors.
Questions people ask
What is the default apportionment method?
Single sales factor is the default. Unless you use the three-factor method, enter the Idaho sales percentage from line 27 on line 37.
Who can elect three-factor apportionment?
Electrical, telephone, and communications corporations, as defined in Idaho Code, and MTC special industries can elect it. The listed special industries are construction contractors, airlines, railroads, trucking companies, television and radio broadcasting, publishing, and financial institutions.
How do I calculate the three-factor apportionment factor?
Add the percentages from lines 14, 27, and 35 on line 36. Divide that total by three for line 37. If a factor does not apply to your business, divide by the number of factors used instead. The instructions give having no employees anywhere as an example of reducing the number of factors by one.
How many decimal places should I use?
Compute the Idaho property, sales, and payroll percentages on lines 14, 27, and 35 to four decimal places.
What do I do with the completed apportionment factor?
Multiply it by the net income or loss from multistate activities reported on Schedules C, E, and F. Enter the resulting amounts on the applicable lines of Idaho Form 43.