The Department of Finance shall receive all light taxes collected, shall keep them in a separate account, and shall pay them out only upon orders signed by the President of the county government and approved by the Director of Finance. They shall receive no additional compensation for the performance of any duty required of them or any of them under this section. If, after payment of all contracts entered into pursuant to this chapter, there remains a surplus in the light account, the surplus shall be applied to reduce the light tax rate for the succeeding taxable year.