Purchasing - A/P 
Purpose
SAP Business One enables you to control the entire purchasing process from purchase orders through processing A/P invoices.
SAP Business One supports various purchasing documents:
Furthermore, you manage additional business transactions using additional purchasing documents:
You can customize all the purchasing documents for your special requirements by using the Form Settings window to combine text row and subtotal row in the document’s contents and by adding additional text or predefined text to the document.
You can base one purchasing document on another. For example, you start with the purchase order and base the goods receipt PO on that purchase order, and then you proceed to the A/P invoice and base it on the goods receipt PO.
Since you create a contractual relationship with the vendor, with the exception of the purchase order, all purchasing documents are legally binding documents. The purchase order is intended, first and foremost, purely as an informational source in SAP Business One.
If you have created the purchasing document with reference to an existing purchasing document, you can use the Base Document option to call up these documents. Position the cursor on the appropriate row and choose Base Document from the Goto menu on the menu bar.
If you have created the follow-up documents with reference to the current purchasing document, you can call up these documents with the Target Document function. Position the cursor on the appropriate row and choose Target Document from the Goto menu on the menu bar. If more than one target documents exists, the SAP Business One displays the last target document.
See also: