I have uploaded a .csv file from 01/04/2020-09/04/2020 successfully but loaded it twice in error. I can't see a way to delete the duplicate transactions?

Welcome back to the Community, @info897.

The uploaded or imported bank transactions (.csv file) will be displayed in the For Review tab in the Banking page. Since there are duplicates, here's how to delete them:

1. In QBO, go to the Banking menu at the left pane to get to the Banking page.
2. In the For Review tab, place a checkmark on the credit card deposits.
3. Click the Batch actions drop-down and hit Exclude Selected. 

They're now moved to he Excluded tab for reference or review, but are not tracked or reported. To completely delete them, here's how:

1. Go to the Excluded tab, then place a checkmark on the credit card deposits.
2. Click the Batch actions drop-down and pick Delete. 

For further guidance, refer to this article: Exclude expenses from downloaded bank transactions.

Just in case, I'll add this article for future reference: Import bank transactions using Excel CSV files.

Please reach out to me in the comment below if you have any other issues or concerns. I'm always here to help. Have a wonderful rest of the day!