Should my daughter file Colorado State Tax Return since she worked and live in D.C i 2019 for 300 days

[ljh885]

she earned 18K, this is the first year she had earned income, she took a gap year and did intern in D.C, but between interns, she came in and out of Colorado, she has colorado driver license, so should she fill colorado tax return as well as DC for 2019?

[Hal_Al]

Simply answer: yes.  The real question is does she file a resident return or a part year resident return. That depends on the details.  Did her internship end and she moved out of DC? What is her intent; will the home and job in DC be permanent? 

DC is reciprocal with all other states.  If she is a full year CO resident, she files a DC  non resident return for a full refund and files a CO return to pay CO tax on all her income.

[TomD8]

To elaborate a bit on @Hal_Al 's answer, DC does not tax non-residents.  However, DC considers a person to be a resident for tax purposes if they "maintained a place of abode in DC for a total of 183 days or more even if their permanent home was outside of DC."   Since your daughter lived in DC for 300 days, she must file a DC tax return.

https://otr.cfo.dc.gov/page/individual-income-tax-filing-faqs

Her income is also subject to CO taxation if her domicile remained in CO in 2019.  A taxpayer can have only one domicile at a time.  To help you understand this, read CO's specific rules and definitions regarding "domicile" in this reference:

https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=6583&fileName=1%20CCR%20201-2%20-%2...

If she has to file in both DC and CO, she should be able to take a credit on her CO for the taxes paid to DC on the income taxed by both.