I'm trying to upload sales invoices what is the best category to place it under please ?

Hello Leighandgjoinery, 

Welcome to the Community page, 

So in Quickbooks Self- Employed you can not upload anything into it, so you will not be able to upload invoices into your Quickbooks Self-Employed account. The only things you can upload into that account type is a csv for your bank transactions and a logo for your invoices nothing else can be uploaded into it.