Use the Write Cheques function: Make the cheque payable to the Vendor you owe the money to. Enter the date for the first instalment. In the bottom section of the cheque, under the Expenses tab, select Accounts Payable. Select the Tax Code and enter the amount you are paying. Tab over to the Customer:Job column and select the Vendor you are paying from the dropdown list. Using A/P with the Vendor Name creates a credit in the Vendor account. Make sure the Print Later option is selected.
When the cheque is exactly the way you want, make a copy of the cheque. Change the cheque date to the next payment date. Continue making copies and changing the date until you have paid all the instalments. From the File menu, select Print Forms>Cheques. When the screen populates, enter the first cheque # and select the cheques you want to print. Print the cheques.
When you receive the bill from the Vendor, enter it as usual. Open the Pay Bills window and apply the credits to pay the bill.