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​Oregon computes taxable income for subchapter C corporations by starting with federal taxable income and then modifying that based on Oregon’s tax law.
Corporations doing business in Oregon are required to file Form OR-20, Oregon Corporation Excise Tax Return.
Corporations not doing business in Oregon, but with income from an Oregon source, are required to file Form OR-20-INC, Oregon Corporation Income Tax Return. If you have tangible or intangible property or other assets being used in Oregon, any income you receive is Oregon-source income.
"Doing business" means being engaged in profit-seeking activities in Oregon that aren’t protected by Public Law 86-272. If the corporation has an Oregon address, generally the corporation will file and pay excise tax. A corporation having one or more of the following in this state is doing business in Oregon:
  • A stock of goods.
  • An office.
  • A place of business (other than an office) where corporation affairs are regularly conducted.
  • Employees or representatives with activities which go beyond the solicitation of orders for sales of tangible personal property.
  • An economic presence through which the taxpayer regularly takes advantage of Oregon's economy to produce income.

Excise tax

Excise tax is a tax for the privilege of doing business in Oregon. It is measured by net income. All interest is included in income, no matter its source.

Minimum tax

Excise tax filers are subject to a minimum tax (ORS 317.090)​. This minimum tax is not subject to the state tax add back provision for Oregon corporations filing Form OR-20 or Form OR-20-S (ORS 317.314).

Filing information

All returns are due on or before the 15th day of the month following the due date of your federal corporation return (May 15 for calendar-year taxpayers). When the 15th falls on a Saturday, Sunday, or legal holiday, the due date is the next business day. The Oregon extension due date is the 15th day of the month following the federal extension’s due date.
If you are a multistate corporation with income from two or more states, you’ll need to apportion, and possibly allocate, your income. For more information, see the instructions for Schedule OR-AP, Apportionment of Income for Corporations and Partnerships.

Federal audit changes

If the IRS changes your federal return for any tax year, you must notify us. File an amended Oregon return and include a copy of the federal audit report. Mail this separately from your current year's return.

If you don’t amend or send a copy of the federal report, we have two years from the date the IRS notifies us of the change to issue a deficiency notice. You must file an amended return within two years of the date of the federal report to receive a refund.