Are tax installment payments for prior years taxes due deductible on either state or federal returns?

[KarenL2]

Yes, the payments to the state are deductible on the federal tax return if you file a Schedule A Itemized Deductions.  Only the amount paid during the calendar year are deductible (even if to pay a past due debt).  Also, the amount of state and local taxes must be higher than sales taxes as you can only claim one or the other.  Your federal tax payments are not deductible.