Welcome to the Intuit Community, @office43.
Yes, you can import your invoices using an Excel or .CSV file in QuickBooks Online. However, you'll need to use a third party application to import your transactions.
Let me guide you through on how to find an app:
If you need further assistance connecting the app with QBO, you can contact the Support team of the product you've chosen.
Should you need anything else with importing your transactions, please let me know. I'd be glad to help.