You can change your Federal and State Tax Withholding through Employee Self Service (ESS) by logging in and clicking on "Pay/Tax Information" and then "W-4". Click on "Edit Federal" or "Edit California" in order to change your respective tax withholdings.

Alternatively, you can go to the "Payroll Forms" and submit the forms electronically by clicking on "W-4 Employee's Withholding Certificate (Federal)" or "DE-4 Employee's Withholding Certificate (State)" under "Informed K12 Forms".

You can always fill out a paper form and bring it into the Payroll Department by going to the "Payroll Forms" site and downloading the forms.

The deadline is always by the end of the 15th of the month in order to take effect on that months payroll. For example, if you turn in the form by the end of April 15th, then the tax withholding will take effect on your April 30th paycheck.

The Payroll Department can only inform you what required fields are to be filled out on the forms. Payroll cannot provide any tax advice. Your tax accountant will be able to guide you on how to fill out your tax withholding forms for your specific tax situation. There is an IRS Tax Withholding Estimator for Federal that is a good tool, you can find it by clicking here. 

After you change your Tax Withholdings, please watch your paycheck to make sure your tax withholdings are your desired outcome.