Tips for final week of income tax filing season

VALLEY – With only one week left until the Tuesday, April 17 income tax filing deadline, the Colorado Department of Revenue (CDOR) would like to share a few tips for Colorado taxpayers who have not yet filed their state income tax returns.

Federal & State filing deadlines

Taxpayers have a couple more days to file their income taxes this year because the typical April 15 deadline falls on a Sunday. Generally, when a due date falls on the weekend or a holiday, it is moved to the next business day. However, the District of Columbia’s observance of Emancipation Day on April 16 will also push the tax filing deadline for federal and Colorado income taxes to the next business day, making the due date Tuesday, April 17.

Returns filed by Tuesday, April 17 will be considered on time. To be accepted as timely filed, mailed returns must be postmarked by April 17. An automatic extension to file is granted until October 15, but there is no extension to pay taxes owed. See form DR 0158-I: 2017 Extension Payment for Colorado Individual Income Tax for the tax payment worksheet and more information on extensions.

Prevent delays

Missing Social Security numbers (SSN) and Colorado Account Numbers (CAN) on forms and/or checks cause processing delays. If the accounting system doesn’t know which tax account to apply the payment to, taxpayers may receive billing notices. Make sure the SSN or CAN is listed on the memo line of the check and is on any documentation mailed to CDOR. This is especially important when a check is sent without a form. CDOR receives thousands of checks each month that do not have an SSN or CAN, resulting in research time to properly credit the taxpayer.

Save time and money

With the deadline quickly approaching, taxpayers can save time and money by filing online. Over 84 percent of taxpayers submitted their Colorado individual income tax returns electronically last year. CDOR encourages taxpayers to e-file because the software will also catch errors so taxpayers don’t have to redo returns due to missing documentation or math mistakes. If a tax return is e-filed, it should not also be mailed.

Taxpayers can file electronically for free using CDOR’s Revenue Online service at without creating a Login ID. Click on “File a Return” under Quick Links. Please remember that filing a tax return on Revenue Online does not automatically set up an account. Taxpayers can file a return without logging into the system. Due to security measures, Revenue Online is not available to taxpayers who are filing Colorado taxes for the first time. Taxpayers also have the option of utilizing tax software or hiring a tax professional. There is a list of accepted tax software on the Individual Income Tax File webpage at


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