If the customer can pay the Catering sales via invoice.
Here's how you do this:
1. After you have chosen the catering you have to save this.
2. After you have saved it, a contract number will appear at the top left. Top right you can see that the status
of the contract is Final and that the installments have been set up.
3. In the catering tab you get an overview of the number of menus ordered through the catering sales.
4. At the tab of the installments you can see that the payment field is empty so that the people of the
accounting know that an invoice must be sent.