It is not an obligation to pay until you have received the good ordered from your supplier.
You can only use purchase order in Quickbooks Pro, Premier and Enterprise.
To record a purchase order in Quickbooks, simply click purchase order on Quickbooks homepage.
A purchase order window will pop up for you to fill in the details of goods you want to buy.
Item: Select the products you want to buy.
Description: Describe products.
QTY; The quantity demanded.
Rate: Enter the cost of the product based on your market price
Customer: optional but used if your customer supplies the products.
Amount: Shown automatically based on rate and quantity ordered.
When you are done, click save and close to record the purchase order in quickbooks accounting software.