Hi robyn-brown,

Thanks for posting in the Community!

Let me guide you on how to undo added and categorised transactions in QuickBooks Online. Here's how:

1. Click on the Transactions tab.
2. Click on Bank transactions, and select the bank account.
3. Click on Categorised tab.
4. Locate and click on the transaction to correct.
5. Click on Undo from the Action column.

The transaction will go back to the For review tab and ready for you to categorise again.

For reference you can refer to this link for a more comprehensive information: Unmatch downloaded bank transactions or move them to another account.

Post again in the Community if you have further concerns. I'll be around to help you.