Were you employed in your previous state? If so, you should request a W-2 from your previous employer.
I was employed in my previous state with the same employer. The only thing that changed is my state of residency half-way through 2020. I should only have one W-2 form with the same employer, but it only includes my current state info in box 16, not the previous state's info.
Does Box 1 of your W2 show your full year's income?
Was your previous state possibly a no-income-tax state?
Box 1 does show my full year's wages correctly.
Box 16 only contains about half of my total wages - box 15 has my new state.
Looking back at my 2019 W-2, box 16 matched my full federal wagers from box 1.
Based on this, I would assume that when reporting my previous state wages, I would subtract whats in my current box 16 from the total federal from box 1?