Turbotax has an amended file checklist, but I misunderstood it. It said to sign and date form 1040X, but it also said if I'm filing a state return the form is located right after the instructions sheet. I thought it meant that I had to include the 1040X with blank A,B,C columns along with the VA 760 form, so I mailed the original 1040, 1040X and VA 760 form to the state.
