Since the order number, of course, varies per event, in MICE you fill in the order number in the event. But where do I exactly add the order number so it is also shown on the invoice?

For this, we have made available a 'Reference' field. You can find the reference field in the pop-up screen that appears while creating or editting an event. It is located next to the group name (see image below).

On the invoice, the order number can be found below the client reference, invoice date and date due (see image below).