Before you consider the domicile of each of your clients, you need to remember that Arizona is a community property state.  She is taxed on half the income from all three states, in the absence of an agreement to disregard community property.  He is taxed on the other half of her Arizona income. New Mexico is also a community-property state, so they pay tax on all his income from there.  New Mexico may give them a credit for some of the Arizona tax paid, and Arizona may give them a credit for some of the New Mexico tax paid.