According to Colorado Department of Revenue “Colorado residents must file this return if they are required to file an income tax return with the IRS, even if they do not have a Colorado tax liability. Otherwise, the Department may file a return on your behalf and our return might not consider your unique tax situation. Also, the only way to determine if you are entitled to a refund is to file a return.”
You must file a Colorado income tax return if during the year you were:
- A full-year resident of Colorado, or
- A part-year resident of Colorado with taxable income during that part of the year you were a resident, or
- A nonresident of Colorado with Colorado source income;
- You are required to file a federal income tax return, or
- You have a Colorado income tax liability for the year.
You MUST file using the SAME filing status on both your federal and Colorado income tax returns. Parties to a Civil Union should refer to federal tax law to determine the correct filing status.