I'm here to help share insights about such an error message prompt so you can set up purchase orders in QuickBooks Online.
The error message saying you'll have to select an account when trying to create a purchase order is related to the transaction detail itself. It means you have entered an amount of transaction but the category detail or the line item selection has no info chosen when trying to save it.
Therefore, let's review each of the line items of your purchase order making sure the category detail or the line item selected is correctly chosen before setting up your transaction. Kindly read and use this article to learn more: Create and Send Purchase Orders in QuickBooks Online.
Now that you're able to create purchase orders, you're also able to generate reports showing what has been expensed and other transaction data based on the financial status you need. Here are the references you can use: Create and Manage Reports in QuickBooks Online.
I've got you covered if there's anything else that I can help you with aside from creating purchase orders in QuickBooks, please let me know by tagging, @JonpriL, in the comments below. I'll be around and ready to help. Take care always and stay safe!
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