You can generate an invoice directly from a ticket.
This is useful if you want to charge for your time spent on a support ticket.
Simply click the new invoice button on the ticket sidebar like this:
You can also use the new automatic ticket timer feature. Simply navigate to a support ticket page and watch the page timer increase.
When you are finished click the Invoice button at the end of the task timer listing and it will generate an invoice for you to manually email to the customer.