Hi @katiekc
You may be able to bulk input your invoices, which would be similar to a shop or e-commerce site for example. This would involve inputting the invoices under a generic client on regular basis (e.g. daily or weekly).
The important thing with this is that you have any documents to back this up. If you’re using other software to produce the invoices, I would say this is sufficient for this purpose.
Perhaps a tool like this would be of some use in this instance? Cash Register Tool