Thanks for your question.
If you pay $10,000 in April 2010 for state income taxes, it would be deductible on your 2010 federal income tax return as an itemized deduction (if you are on the cash basis method - most taxpayers are). So you would have to wait to claim it next year when you file your 2010 tax return.
Any state income tax paid in 2009 (such as 2008 state tax paid in 2009, 2009 estimated state income taxes, etc) can be claimed on your 2009 federal income tax return.
Hope this helps,
Thank you--I understand,however, I needed to know if it would also be deductible
for CA state taxes when I file next years return.
No, CA state income taxes are not deductible on a CA state income tax return. You would have to add back the state tax itemized deduction on Schedule CA 540, line 39.
Let me know if you have any questions.