C Corporation Filing Information
First, complete the federal income tax return you will file with the Internal Revenue Service (IRS). You will use figures or data from your federal return on your Colorado income tax return. The Colorado Department of Revenue offers a free e-file and account service called Revenue Online to file your state income tax. Visit the File Online page for more information.
Extension of Time to File
Calendar year returns are due on Wednesday, April 15, 2020. If you are unable to file by your prescribed due date, you may file under extension. This will allow you an additional six months to file your return, or until Thursday, October 15, 2020 for traditional calendar year filers. However, the extension to file does not allow you to extend your payment due date. You must pay at least 90% of your tax liability by the original due date of your return and the remainder by the filing extension due date to avoid delinquent payment penalties.
Amending a Return
If an amended return is filed with the IRS, or if the IRS changes the content of the return, an amendment must be filed with Colorado. Use Revenue Online or the DR 0112X to amend the Colorado return. If the corporation operates in multiple states, the Department will accept the revenue agent report (RAR) in lieu of an amended return.