Nonresidents are subject to Arizona tax on any income earned from Arizona sources.
If your child's income exceeded the AZ filing threshold for non-residents, he/she must file a non-resident AZ tax return.
He/she must also file a CO tax return, since ALL the income of a CO resident is taxable by CO, regardless of its source. But a credit may be taken on the CO tax return for the taxes paid to the non-resident state, thus eliminating double taxation.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
