How do I remove duplicate transactions ?

I can give you the steps on how to remove the duplicate transactions, claire-wright.

If these transactions are from the banking section, then you can exclude them by following these steps:

1. On the left panel, click Banking.
2. On the For Review tab, find and put a check mark on the duplicate transactions you want to remove.
3. Click the Batch Actions drop-down menu, and select Exclude Selected.

For reference, here's and article: How to exclude expenses from downloaded bank transactions. You can also delete them on the Excluded section.

To delete transactions recorded in QuickBooks Online, I've got this article for the steps: How to void or delete an invoice or other transactions.

We are always here if there's anything else you need help with QuickBooks. Have a great day!