How do I book an additional service on a guest invoice?

You are in the invoice area of a reservation (How do I open a guest invoice?), and want to add services to a guest’s bill.
Click ‘Add Products’ at the top right corner of the screen.

A new view opens displaying your article and product groups, from which you can select the desired product.

Left mouse click to check the product you want to add to the guest invoice. The bottom line allows you to override the product name and price, if you have allowed for such editing in the master data. If you would like to add a particular product more than once, then simply adjust the number accordingly. Click ‘Apply’ to add the product to the guest’s bill.

The window then closes, and the service/product is posted accordingly on the guest invoice.