I ended up doing this a little more simply. Rather than working with percentages, I took my husband's taxable income, as provided by TurboTax, and divided it by the number of working days in 2018 (261) to get a daily wage figure. I then calculated how many working days he was in VA and multiplied that number by the daily wage amount. That gave me the portion of his taxable income that is attributable to Virginia.
