Return 
For legal reasons, you cannot delete a delivery or invoice that you enter in SAP Business One, or change accounting-relevant data in these documents. However, the customer might send the goods back for various reasons, or you might have made a mistake when you entered the documents.
In such situations, create a return document.
When you enter a return document, you can reverse the posting of a delivery. When you create the return, the system corrects the inventory quantities. If your company runs a perpetual inventory, creating a return automatically generates a journal entry that updates the inventory value.
The return is the clearing document for a delivery. Therefore, if an A/R invoice has not yet been created for the delivery you want to reverse, use the return document. If you have already recorded an invoice, use the A/R Credit Memo function to correct values and quantities for the transaction in SAP Business One.
When you create a return document based on a sales order, you can choose to reopen the item quantity of the order. To be able to do so, the checkbox Enable Reopening of Orders When Creating Returns Based on Orders must be selected in the document settings. For more information, see Document Settings: Per Document Tab.
Reopening the item quantity has the following consequences:
The status of the sales order changes to Open.
The open quantity is increased by the item quantity in the return document. If the sum of the remaining open quantity plus the returned quantity is higher than the quantity in the original order, the open quantity is increased up to the quantity in the original order.
The delivered quantity is decreased by the quantity in the return.
For service type transactions, the open amount is increased accordingly by a value equal to the value from a return line. If the sum of the remaining open amount plus the returned amount is greater than the total amount for the original order line, the total amount is used as the open amount.
If there are any freight charges related to the returned item, these charges are reopened in the same way as the item quantities.
If the item is managed by batches, the returned batch-allocated quantity is increased by the quantity from the return line.
To access the window, choose 
Sales – A/R 
Return 
.