This page of the instructions describes the creation of withholding tax paid to the Finnish Tax Administration.
Add your tax office to the business partner register as a supplier and save the office’s information.Create an invoice for the supplier, i.e. the tax office.Enter the finished withholding tax invoice on account 9900 Taxes during Fiscal year and earlier years and on account 2880 Payment transactions account.You can then copy the invoice for each month.
When copying the invoice, you should check that each invoice has the correct date.Always copy the bank reference code to the next invoice.The business ID without the verification number (in bold in the example) is included in the middle of the bank reference code and followed by a changing monthly number (in italics in the example), so the part after the business ID changes for each invoice.You should therefore enter the whole year’s taxes in advance.However, you should not queue the taxes for payment until two or three months before the due date, since you may wish to change the withholding amounts during the year.
Sample bank reference code: 12345083692206167890