How California taxes severance
California taxes severance as regular income, and for withholding it's treated as supplemental wages: employers withhold a flat 6.6% for the state (10.23% applies to bonuses and stock options) on top of the 22% federal supplemental rate, Social Security, and Medicare. Withholding isn't your final bill — California's brackets run from 1% to 13.3%, so what you actually owe is settled on your state return based on your full-year income.