To view an Invoice, navigate to the Client Log for the Client in question and click the Invoice from the list.
Tip: A quick way to access the Client Details for a client is to locate an appointment with them in the diary, click it and choose Client Details to be taken straight there. You can then access the Client Log.
Access the invoice by clicking the Heading. From the next screen, there is the option to mark the Invoice as paid by choosing a payment method from the drop down list.
From here you can also Download and Delete the invoice.
Emailing an Invoice
If you simply want to email a copy of the Invoice to the Client (or any other email address(es)) you can open the Invoice from the Client Log as described above, click to Email Invoice, check / enter the email address(es) and click Save.
This will not make any updates to the Invoice itself (unless of course you have chosen a payment method) and will schedule the email to be sent.