If we have a professor who speaks at different universities across the country (his main job is at a University in CA), and earns 1099 income from those universities, is he required to file taxes in those states which the university is based out of? Is there an exception for professors?
Yes, he is to report his income in each of the other states if he exceeds the minimum threshold required for filing a tax return in those states. Each state has a different filing requirement. I am not aware of any exception for professors. He may have deductible expenses to help offset that income.