Can I add old invoices my customers have paid from before I joined quickbooks?

Thanks for joining the Community, bouncenboogie22

You can enter past invoice and invoice payments in QuickBooks Online. Simply create the transaction and change the date to the back-dated date.

Please note, if you've filed at least one return in QuickBooks, adding a transaction with VAT may create an exception on your open return. If you have any further Q's on this, get back to us below!