Subtractions are items that are not taxable in Kentucky but may be taxable on the Federal return. In Kentucky, one of the biggest subtractions is Pension. If your wife drew income from a pension (even cashing out a 401-K prematurely), that income is not taxable in Kentucky unless it is more than 31,110. This is the most likely source of a subtraction (or taxable Social Security reported as income on the Federal Return; that's not taxable in Kentucky either).