State tax filing

Hello-

I'm wondering in what tax year the B&O tax can be deducted on federal tax return.  Specifically, if I don't pay part of my B&O tax for this year until January next year (because I won't know my total receipts until the end of this year), can I take the deduction on this year's tax return -- since that's the year the taxes were paid for -- or do I need to take the deduction on next year's tax return (the year when I wrote the check for the B&O tax).

Thank you!