Filing & Payment Deadlines
If you cannot file your Colorado income tax return by the extended deadline of May 17, 2021, you may take advantage of the state’s automatic six-month extension of time to file.
There is no form to fill out to notify the Department of Revenue that you are taking the extension, however there is no extension for tax due. The extension applies to filing Colorado income tax information, either on paper or electronically, not to any state income tax you may owe. If you expect to get a refund this year but do not make the filing deadline, you can still file your state income tax on or before October 15.
There is no extension for tax due. If you owe state income tax, 90% of the tax liability must be paid on or before May 17th to avoid penalties. Any remaining balance due would be subject to interest only. If you owe tax, you must either pay through Revenue Online or submit your payment with the Extension Payment Form (DR 0158-I).