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Oregon corporate amended returns
If you change taxable income by amending your federal return, or if you are a 20-INS (Oregon insurance excise tax return) filer and amended your annual statement, you must file an amended Oregon return within 90 days. Attach a copy of your amended federal return to your amended Oregon return and explain the adjustments made. Use the form for the tax year you are amending and check the “Amended” box.

If you filed Form 20-S (Oregon S corporation tax return) and later determined you should file Form 20 (Oregon corporation excise tax return), check the “Amended" box on Form 20.
If the IRS changes your federal return for any tax year, you must notify us. File an amended Oregon return and attach a copy of the federal audit report.

If you do not amend or send a copy of the federal report, we have two years from the date we’re 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.

Mail your amended return separately from your current year’s return to:

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

Net operating losses

Do not amend your Oregon return if you amend the federal return to carry a net operating loss back to prior years. Oregon allows corporations to carry net operating losses forward, but not back.

Prior tax liability

When preparing your amended return, on the estimated tax payments line, enter the net excise tax from the original return or as previously adjusted. Don't include penalty or interest payments.

Payment with your amended return

If paying additional tax with your amended return, you must include interest with your payment. Interest is fig­ured from the day after the due date of your original return up to the day we receive your full payment.

Pay all tax and interest due when you file your amended return or within 30 days after receiving a billing notice from us to avoid being charged a 5 percent late payment penalty.

Do not make your amended return payment by Electronic Funds Transfer (EFT) or make an electronic payment when e-filing your amended return. We accept check or money order mailed separate from your e-filed amended return or included with your paper-filed amended return. Make sure to write “Amended Payment” on your check or money order and include a completed Form 20-V with the “Amended” box checked.

Important: If your check or money order is not clearly marked as “Amended payment,” our system will apply the pay­ment to your account before the return is processed causing an automatic refund which could result in additional penalty and interest.

Protective claims

An amended return may be filed as a protective claim to extend the statute of limitations for a refund request for a tax year while an issue is being litigated. Check the “Amended” box and write the words “Protective Claim for Refund” at the top. We’ll also accept a written letter in place of an amended return. Include the same information in the letter as is required on an amended return. We will hold your protective claim until you notify us the litigation has been completed.

Visit our corporate taxes webpage for more information.

Note: If a deficiency is assessed against any taxpayer as a result of the retroactive adoption of federal law changes, we will cancel any penalty or interest pertaining to these changes. If a taxpayer files an amended return showing a refund due based on the retroactive adoption of federal law changes, we won't pay interest.