If you have Xero or QuickBooks Online integration enabled, we don't have direct control over invoice templates within SortScape. Rather you will need to edit the invoice layout within those systems.
If you have Xero integration enabled, you can select which Xero Branding Theme to use when creating Xero invoices from SortScape. To do this, go to the Xero settings screen in SortScape and change the "Default branding theme" setting. (You need to be connected to Xero to change this.)
If you are using SortScape's built-in invoicing, then you can upload your logo and add payment instructions to your email template on the Invoice Settings screen.