I am trying to create a purchase order. All info has been filled but it keeps asking for "You must select an account for this transaction."

Hello @OSPA_Mai,

Thank you for posting here in the Community. I can help you fix the error message when creating a purchase order in QuickBooks Online.

When you create a purchase order, you have the option to use Account/Category details or Item details. Please make sure to include an account or item for those lines you've entered an amount.

Leaving it blank will trigger the error when saving the transaction (see sample screenshot below). 

If the issue persists, the browser's stored cache may be full. It causes unusual behavior in QuickBooks, like the unusual behavior on your end.

I'd suggest you start by logging into your account using a private browser. This way, you can access sites without storing any data in the cache. It's a great way to isolate browser-related issues.

If you're using Mozilla Firefox or Microsoft Edge, press the CTRL + Shift + P shortcut on your keyboard. For Safari, hit Command + Shift + N. Press CTRL + Shift + N if you're using Google Chrome.

From there, create the purchase order (PO) again and check the outcome. If it works fine, let's clear out your browser's cache to have a clean slate.

In case private browsing doesn't work, use another supported web engine. It will help us identify where the issue is coming from when creating a PO.

For additional reference, you can use the following article to apply purchase orders to transactions, as well as how to add partial payments: Add purchase orders to expenses, bills, or cheques in QuickBooks Online.

Please let me know if you need more assistance entering transactions or resolving error messages. The Community and I will be here to help you.