The Invoice Reference is a Reference that you can set for your customer. This is typically one of the Client Contacts for the client.
To add an Invoice Reference, head over to the Case Case, Details-view, under the Payer Section.
Click on the Enter invoice reference text...
The following text box field will appear. Click anywhere in the field and start typing in the field the reference text you wish you add.
Once you are done typing, click anywhere outside the field and the invoice reference text will be saved automatically.
1. Ensure that you are either a Client Manager, a user with 'Assistant'-role, or 'Administrator'-rights to be able to add an Invoice Reference.