PURPOSE: To input both financial data and taxational data at one time through the use of a data input means at the time of the generation of the financial data by coordinating a title code and an income tax classification code with each other.

CONSTITUTION: An integrated dile 3 generated from payment data (a) is made the input, and for data having the title code of an annual expenditure file 8, the amount of payment of the integrated file 3 is made capable of being paid out by adding it to the amount of payment of the annual expenditure file 8, and financial processing 6 is executed by subtracting the amount of payment from a payable amount of money. Besides, at that time, a written order for payment 9 showing a payment slip number, the date of payment, the title code, the amount of payment, and creditor information is issued. Besides, the 'account statement of an income tax collected amount' 12 is generated from the data stored in the integrated file 3. Further, the amount of year-end adjustment is calculated from the deduction data of a creditor file 4, and a taxation information file 10 classified by an individual is generated, and at that time, a withholding tax collection slip 11 on which a prescribed total amount after the year-end adjustment, the amount of deduction, the amount of an income tax are displayed is tabulated.