Business Income Tax Filing

Due date

File your return and pay any tax on or before the 15th day of the fourth month following the close of your tax year.

  • For a calendar year filer, this is April 15.
  • If the last day for filing a return falls on a Saturday, Sunday, or legal holiday, the return is on time if you file it on the next business day.

Please contact us if you forgot to file a tax return.


The Tax Commission, with the IRS, provides electronic filing of federal and state corporation income tax returns.

These software companies provide electronic filing of business income tax forms 

Form ID K-1

Use Form ID K-1 to provide the partner, shareholder, or beneficiary of a pass-through entity with information required to complete the pass-through owner’s Idaho income tax return.

Learn more about Form ID K-1 

Bonus Depreciation

Depreciation is a federal income tax deduction that lets a taxpayer recover the cost of capital expenditures over time. Read our guide on bonus depreciation.

Idaho NOL: 5 most common mistakes

This video applies to NOLs through tax year 2018.

Learn the five most common mistakes seen on individual returns claiming an Idaho net operating loss.

Combined reporting

Visit our Combined Reporting page.


Need more time to file? See if you qualify. Read our guide on valid extensions for filing.