The DC tax booklet instructions are contradictory.
From page 15 of the DC tax instructions:
"The calculation of tax liability for a part-year resident is pro-rated based on the income earned in DC, during the period of residency."
From the instructions for Line 8, on page 16 of the instructions:
"For each type of income reported on your federal 1040 or 1040-SR, determine the amount you received when you were domiciled in DC."
The DC instructions do not specifically cover the situation in which a bonus is earned while a DC resident but received while a DC non-resident. But the usual rule is that a bonus is taxable by a state to the extent that it represents compensation earned from work carried out within that state. The DC page 15 instruction is in accord with that. (It is always true that the resident state may tax all income received as a resident of that state.)
My recommendation is to follow the page 15 instruction and pro-rate the bonus, allocating the appropriate portion to DC. If you do that, then you can claim an "other state credit" on your CO return for the taxes you pay to DC on the portion taxed by both entities. This will prevent you from being double-taxed.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
