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;
AND
-
You are required to file a federal income tax return, or
- You have a Colorado income tax liability for the year.
https://www.colorado.gov/pacific/tax/individual-income-tax-quick-answers at Filing Requirements.
