Enable a button on the invoices so that you can easily create a new sales invoice. A "Save and New" would be handy so that once the sales invoice was created you can hit the button and create a new invoice instead of having to go through the customers again. This would save a lot of time when creating 50+ invoices at a time.
It would also be handy if the "save and new" button would continue with the previous invoices date rather than the current date.
Also it would be quicker if we did not have to enter the "/" in between the dates and could just enter the numbers.