The Illinois bonus money you received in 2019 after becoming a California resident is taxable by both states.
It is taxable by Illinois because it was compensation for work performed in Illinois.
It is taxable by California because California taxes residents on all income, regardless of source.
So the IL bonus must be included in CA income on your 2019 amended CA return.
Your amended 2019 CA return should have no effect on your 2020 tax returns.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
