Each county assessor, auditor, treasurer and tax collector shall file annually with the board of supervisors of his county, itemized statements showing the additional expenses to his office caused by performance of the duties imposed upon him by this chapter. Upon the filing of such statements the board of supervisors, by an order upon its minutes, shall deduct such expenses from the assessment money of the district while in the hands of such tax collector and transfer the amount deducted into the county general fund.