Do you have an NOL or a Capital Loss Carryforward? Depending on the state, it might be necessary to start with the negative number to account for any state adjustments (items deducted Federally that the state doesn't allow), so that, if any adjustments result in producing a state tax liability, this can be reduced because you started from a "state negative income" calculation point. A negative number otherwise will have the same effect as $0 income: $0 state tax liability.