CL6,
CO part-year and nonresident income tax is computed by first totaling all income from all sources and then determining what portion is CO income. The ratio of the two is applied to things like the $300 charitable deduction and the portion of computed tax actually due CO. (For some items, the ratio only includes earned income.) The CO webpage
https://tax.colorado.gov/income-tax-topics-part-year-residents-nonresidents
Gives you the details on how to apportion the various federal deductions. I can
