Colorado corporate, partnership and S Corporation income tax returns are due to be filed three-and-one-half months after the close of the corporation or partnership tax year. The tax year may not necessarily be a calendar year. But if it is a calendar year, the returns were due April 15.
An automatic six-month extension of time to file with Colorado is allowed. For calendar year filers, the Colorado extension filing deadline is Oct. 15.
The Colorado Department of Revenue wants to remind taxpayers that the Colorado corporate and partnership returns may be filed electronically, free of charge, through Revenue Online.
Sign Up for Revenue Online by creating a Login ID and Password to access your corporate or partnership tax account. Then log in with the ID and Password you create and click on File Now to submit the return online. Corporate and partnership returns may be amended in Revenue Online as well.