Emancipation Day - Income Tax Due Date

The filing due date for 2017 Colorado income tax returns is Tuesday, April 17, 2018, rather than April 15. Emancipation Day (Monday, April 16)  affects the due date this year. Extensions are due Monday, October 15.
In some years, the District of Columbia’s observance of Emancipation Day can affect the nation’s filing deadline. Emancipation Day falls on Monday, April 16. This will push the tax filing deadline to the next business day for federal and Colorado income tax making the due date Tuesday, April 17, 2018. Returns filed on Tuesday, April 17 will be considered as timely filed. Revenue Online will accept returns as timely filed until midnight. Returns that are mailed must be postmarked by April 17.
An automatic extension to file is granted until Monday, October 15, 2018, but there is no extension to pay. See page 27 of the 104 Booklet for more information on extensions.