During a purchase or sales flow, the purchase or sales order will be closed once you receive or deliver it, and you may forget about it after you put the information into the system. But you can reopen and update your orders in SAP Business One when goods are returned.
SAP Business One may help you with a simple click. Go to Administration > System Initialization > Document Settings, click Per Document and choose Sales Order. Finally click box “Reopen Doc. by Creating Returns/Goods Returns/Credit Memos Based on It”.
Then when you create a document, such as Returns, Goods Return, or Credit Memo, you will see a window pop out and ask you if you want to reopen the respective document or not.
If you choose Yes, the sales or purchases order will be reopened, and you are able to take further action on the document.
Learn more about sales and purchase orders with this article: Partially Delivered Order in SAP Business One.