Entering a Goods Receipt for a Purchase Order 
Prerequisites
If you have received the delivery note from the vendor, and you have verified that the delivery was based on a purchase order, you can enter the goods receipt in the R/3 System.
Automatic Generation of Purchase Order at Goods Receipt
If you receive a delivery for which no purchase order exists, you can still post the goods receipt. In this case, the system generates an automatic purchase order at the vendor, if this has been set for each movement type in Customizing. The goods receipt is valuated at the price defined in the purchasing info record in the first instance. To do this, a purchasing organization must be assigned to the receiving plant. You cannot post movements into GR blocked stock with this function.
In the automatic generation of purchase order process, you can also verify an invoice immediately after the goods receipt is posted.
This function is useful if a vendor delivers urgently required material for which you could not enter a purchase order for time reasons.

You can only generate purchase orders automatically for valuated materials and for movement types for which you can enter goods receipts for purchase orders, for example, movement types 101 and 161. For a future release, SAP plans to include this function for non-valuated materials.
Return for Purchase Order
When you are posting a goods receipt for purchase order, you can also enter items that you want to return to the vendor. To do this, you no longer have to reference the purchase order with which the goods were originally delivered. From the item overview, choose Process
® Without purchase order ® Enter and enter the default values for the new item. Choose 161 (Return for purchase order) as the default value for the movement type. Enter the data for the returns item and post the document.In Customizing, you can configure the system so that a purchase order is generated in the background for the returns items. This purchase order is required if you want to carry out invoice verification for the credit memos issued by the vendor for the returns.
Procedure
This takes you to the initial screen for this function.
If the quantity delivered is intended for the warehouse or for consumption/usage, select Movement type ® PO to warehouse (Movement type 101 ).
If the total quantity is to be posted to GR blocked stock, choose Movement type ® PO to blocked stock (see section Goods Receipts Into Goods Receipt Blocked Stock).
If you selected PO number not known, you can specify search criteria for the purchase orders on the initial screen. The system then displays a list of purchase orders. Select and copy the required purchase order items.
The item selection list is displayed. This list contains all of the purchase order items that satisfy the criteria entered.