Thanks for joining the thread, @BestMum.

First, I'd like to thank you for taking the time to perform the steps provided by the previous representative. Know that this isn't the kind of experience that we would want you to have here in QuickBooks. Please be aware that if QuickBooks can't recognize the transaction, it'll automatically allocate it to uncategorized expenses.

Since you've already switched off the prefill feature and the issue persist, you can consider accessing your QBO company in an incognito or private browser. This way, you can access your company with a clean slate. You can use the following shortcut keys:

• Chrome: Ctrl+Shift+N
• Firefox: Ctrl+Shift+P
• Safari: Command+Shift+N

Once you're in, try to perform what you're trying to accomplish earlier. If it works and it stops to prefill the details, you can proceed to clear your browser's cache. Refer to this article for the steps: Clear cache and cookies to fix issues when using QuickBooks Online.

You can also use other compatible browsers if the issue persists. Refer to this article to see the list of compatible browsers in QuickBooks Online: Other browsers.

@BestMum, if there's anything else that I can help you with, know that you can always get back to me anytime. I'll be more than happy to help you out again. Take care.