I raised a credit note to correct an invoice but it appears in the wrong account in QB. Can I find it to UNDO it and categorise to the correct account?

It's nice to see you here in the Community, @chgreenaway. I'm here to provide steps so you'll be able to fix the account of the credit note in QuickBooks Online (QBO).

QBO places credit notes into accounts that are based on the items included on the form. To ensure they are allocated to the correct one, I recommend double-checking the accounts of the items you've listed. Here's how:

1. In your QBO company, select the Sales menu.
2. Then, choose Products and Services.
3. Double-click on the item you added to the credit note and scroll down and review the accounts.
4. You can also change their accounts by following the steps in this article: Change the account for a product/service item. 

For reference in managing credit notes in QBO, feel free to check this article: Create and apply credit notes or delayed credits in QuickBooks Online. 

Once done, run a report again to verify that the form is now assigned to the correct account.

You may also want to modify your sales forms templates such as invoices to control what info will show. To get started, check out this link: Customise invoices, estimates, and sales receipts in QuickBooks Online.

You're always welcome to post back here if there are any more questions about correcting credit notes accounts. I'd also appreciate it if you can share updates on how the steps work. I'm always here and ready to lend a hand. Have a good one.