Hello there, @louisgeorges2000.
It's nice to have you again in the Community. I can help share some information about importing invoices and billing transactions.
At this time, we don't have the option yet to import these transactions into a new QuickBooks Online account. The only way, for now, is to manually add these transactions so that you'll be able to see your client's history charges.
Adding this option would be a great addition to our features. I'd encourage you to send your feedback so that our Product Developers can consider this improvement in the future update. You can use this link to send your feedback straight to our development team: http://feedback.qbo.intuit.com.
Let me know if you have other questions. I'm here to help in any way I can.