In rare cases when you have to dispatch an order at a loss, follow these steps to set up the order for dispatch.

Enter negative amount for the Broker Fee in case when your are losing money on an order.  In the example below, the customer will still see that the total is $1550, but you will see that you have lost money on that order.

You also have to set up Complex Payment Terms on that Order so that the carrier will see that they are receiving $1600 from you, like this: