Select the appointment you wish to invoice. The appointment details will show on the left. Select the Complete Sale button. 

This will bring up a screen that details the invoice items. You can add additional items at this time using the search field. You can also add notes to the invoice if needed. 

Select the Take payment button. 

The Take payment screen will appear.  

If required, you can split the sale over several payment methods (e.g. card and cash).

To do this, select the + Add another payment button and select the payment type and amount. 

Select the Complete payment button.

If you wish to print a receipt make sure the Print a Receipt check box is checked.

Once the payment has been completed, you can view the invoice by clicking on the appointment in the calendar and then on View invoice.