You may deduct California state income taxes which were garnished from your wages on your federal tax return - schedule A - www.irs.gov/pub/irs-pdf/f1040sa.pdf line 5 - to do so - you should itemize and choose to deduct income taxes (and not general sales taxes)
You may not deduct California state income taxes which were garnished from your wages on your California tax return - but that amount is treated as taxes paid (similar to taxes that were withheld from wages) and will reduce the amount you owe.
You should include that amount into the line 72 - 2009 CA estimated tax and other payments. - http://www.ftb.ca.gov/forms/2009/09_540.pdf and it will be credited against your total tax liability.
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