After you file

@salg8nor Yes it is double taxation which is why Michigan will give you a credit for tax paid to California on the Mi tax return. 

In the Michigan section, you'll see the screen Take a look at Michigan credits and taxes.

In Other credits, select Other State Tax Credit. If you do your nonresident California return first, the numbers in this section will auto populate. If you started MI first, delete MI, complete CA, then add MI.