"I checked the bonus paycheck was 9/1-9/15 period. I became a CA state resident on 8/31. Do I prorate this part as well?"
If the paycheck was received after 8/31, you don't pro-rate with regard to CA tax.
"So it sounds like I need to report prorated stock award to VA state tax and all the bonus to CA state tax..."
Correct. Note that you may claim a credit on your VA tax return for the tax paid to CA on the portion of the bonus that is taxed by both states. Therefore that income is not-double-taxed.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
