Hello there, sales-windshield.

To resolve duplicate data within QuickBooks Online, we'll have to delete them manually. If these are uploaded transactions, let's follow the steps below:

1. Go to Sales on the left menu.
2. Within the Invoices tab, tick all the duplicate transactions next to the Date column.
3. Click the Batch actions drop-down arrow. Then, Delete.
   

If you mean that these are items, we can only make them inactive. Here are the steps to follow: 

1. Go to Sales on the left menu.
2. Select the Product and Services tab.
3. Tick the duplicate items.
4. Click the Batch actions drop-down arrow. Then, select Make inactive.
   

I'm adding an article that contains information on how you can manage sales transactions and expenses: 

• Manage Customers and income.
• Manage Suppliers and Expenses. 

Let me know if you have other questions or referring to something else. Take care and stay safe always!