All disbursements shall be made only on regular vouchers issued by the city administrator or city clerk, duly authorized by the council, countersigned by the mayor and the treasurer, which shall indicate the fund out of which the disbursement shall be made. Each order when signed by the city clerk, countersigned by the mayor and the city treasurer, shall become a check payable to the payee at the bank indicated thereon. But no such order or check shall be issued until there is money to the credit of the fund out of which it is to be paid, sufficient to pay the same together with all then outstanding encumbrances upon such fund. No claim against the city shall be allowed unless accompanied by an itemized bill and voucher, payroll, or time sheet signed by the responsible officer who has personal knowledge of the facts in the case and vouches for the correctness and reasonableness of the claim. The council may by ordinance make further regulations for the safekeeping and disbursement of the funds of the city.