As of November 1, 2009, employers in California will be using a new state income tax withholding table thanks to ABX4-17. This law increases the amount of income taxes withheld by 10% based on existing claimed exemptions. This law also increases the rate of withholdings for supplemental wages, such as exercised stock options and bonuses. As of January 1, 2010, you can also thank ABX4-18X for the imposition of a 7% backup withholding for certain payments to non-employees, such as independent contractors, where otherwise required under the Internal Revenue Code.