According to Colorado FYI 6:
A Colorado Resident is an individual whose state of domicile is Colorado or the person qualifies as a 'Statutory' resident. Domicile is determined by voter registration, vehicle registration, driver's license, school registration, property ownership and residence of spouse and children. A person is considered a 'statutory' resident a permanent place of abode is maintained and they spend more than 6 months of the tax year in Colorado.
A Colorado Nonresident is an individual that did not have a permanent home inside Colorado at any time during the year. Temporarily living in Colorado without the intention of staying does not make you a Colorado resident.
A Colorado Part-Year Resident is an individual that was a resident for only part of the year. This includes persons that move into Colorado with the intention of making Colorado their home. Also included are residents that move out of Colorado with the intention of making another state their home.
If one spouse is a resident and the other is not, file form 104PN for Part-Year Resident/Nonresident. The resident spouse will report all of their income while the nonresident spouse will only report Colorado source income.
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