Figure 13.4 present a DFD for establishing accounts payable.(7. This process is also known as invoice verification or invoice matching.)
As shown by bubble 1.1, the first step in establishing the payable involves validating the vendor invoice.
This process is triggered by receipt of the vendor invoice, a business document that notifies the purchaser of an obligation to pay the vendor for goods (or services) that were ordered by and shipped to the purchaser.
Figure 11.5 in Chapter 11.5 (pg. 396) depicts a typical invoice screen.