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Subchapter C Corporations

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Oregon's computation of taxable income for subchapter C corporations begins with federal taxable income and is then modified as required under Oregon tax law.
Corporation income and excise tax regulations are explained in Oregon Revised Statutes and Oregon Administrative Rules (ORS and OAR) chapters 317 and 318, respectively. 
Corporations not doing business in Oregon, but with income from an Oregon source, are required to file Form 20-I, 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 and, your company must file an Oregon Corporation Income Tax Return.
Corporations doing business in Oregon are required to file Form 20, Oregon Corporation Excise Tax Return.
"Doing business" means being engaged in any profit-seeking activity in Oregon not protected by federal public law 86-272. If the corporation has an Oregon address, generally the corporation will file and pay excise tax. A taxpayer having one or more of the following in this state clearly is doing business in Oregon:
  • A stock of goods.
  • An office.
  • A place of business (other than an office) where affairs of the corporation are regularly conducted.
  • Employees or representatives providing services to customers as the primary business activity (such as accounting or personal services), or services incidental to the sale of tangible or intangible personal property (such as installation, inspection, maintenance, warranty, or repair of a product).
  • An economic presence through which the taxpayer regularly takes advantage of Oregon's economy to produce income.
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 what its source. This includes interest on obligations of the United States, its instrumentalities, and all of the 50 states and their subdivisions.

Minimum tax
Excise tax filers are subject to a minimum tax.
Forms 20 and 20-S, Oregon corporation minimum tax is not subject to the state tax add back provision of 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 (April 15 for calendar-year taxpayers). When the 15th falls on a Saturday, Sunday, or legal holiday, the due date is the next business day.
If you are a multi-state corporation with income from two or more states, you will need to apportion and possibly allocate your income. Detailed information can be found in the instructions for Schedule AP, Apportionment of Income for Corporations and Partnerships.
ORS and OAR chapter 314 contain the provisions for apportionment and allocation.

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

Oregon Department of Revenue
PO Box 14777
Salem OR 97309-0960

If you do not amend or send a copy of the federal report, the Oregon Department of Revenue has two years from the date the department is notified of the change by the IRS to issue a deficiency notice. You must file an amended return within two years after the date of the federal report to receive a refund.

Send us an email. We answer most inquiries within two business days.
General inquiries: corp.help.dor@oregon.gov