How to create purchase order from sales receipt?

Hi there, 

Thanks for reaching out to the Community for help with your question. Purchase orders are a great feature in QuickBooks Online. I'd be happy to explain how they work and when to use them. 

A purchase order (PO) is a document you send to your supplier to:

•     state your intent to buy products or services,
•     define the details of the purchase (such as quantities and prices), and,
•     (if they accept your PO) an agreement with them to receive products or services under the given terms

Since purchase orders are a supplier transaction, and a sales receipt is a customer transaction, these two transaction types cannot be linked together. You're able to add a purchase order to a supplier transaction, such as an expense, cheque or bill. Take a look at this article to see how to do that: Apply a purchase order to a supplier transaction.

Here's an article that may help you better understand all aspects of the purchase order transaction: How to use purchase order. This article goes over the following processes: 

• How to turn on a purchase order
• How to enter a purchase order
• How to apply a purchase order to a transaction
• How to receive or pay part of a purchase order
• How to run a purchase order report

I hope this helps to answer your question. Let me know if there's anything else I can do to help. 

Have a great day.