Hi Niko74.
 

It's a great way to ensure that records are organized and intact. Let me guide you how to manage duplicate transactions in QuickBooks Online (QBO).

When activating the new bank account connection, duplicates will be imported into your transactions in QBO. The best way to avoid this is to exclude the duplicated transactions by selecting them.
 

Here's how:

1. Go to Transactions, then select Bank transactions.
2. In the For review tab, select the checkbox for each transaction you want to exclude.
3. Select Exclude.

All excluded transactions will be stored in the Excluded tab and they won't be added to QuickBooks or downloaded. You can also undo all transaction in the Excluded tab to bring it back to the For review tab.

You can refer to this article to know more about managing you transactions: Categorize online bank transactions in QuickBooks Online.
 

Just hit reply and share your thoughts if you have further questions about bank connection. The community team is happy to help you!