Hi lukeish,

Thanks for joining the thread. 

You can exclude the duplicate transactions in your For Review section to avoid duplicate entries on file.

1. Click on the Transactions tab.
2. Click on Bank transactions.
3. Locate and click the bank account.
4. Under For review, click or select the duplicate transactions and click on Exclude.
5. The transactions will move to the Excluded tab.
6. Under Excluded tab you can select the transaction and click on Delete.

For reference you can also check this link to learn more about editing and categorising transactions in QuickBooks Online.

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