First, you need to create a loan instrument with the option "Has mirror deal" active. Initially, when creating an instrument you are unable to see the "Has mirror deal". Once the mirror loan has been saved for the first time, you can edit it and then you can see this item and activate it. Also, you must set the default cross instrument for the main instrument. For example, if you are normally creating the loans from the parent company perspective - where the parent is usually lending (so the main loan is an INV instrument) - the mirror instrument should be a loan instrument.
Please note that you have to make sure that the counterparty of the loan is an entity.
After you have created the main loan, a "Create mirror loan"-icon appears in the loan view right next to ‘Copy icon’ in the top right section of the agreement view. Save the mirror loan and then you can start to run reports and accounting from a mirror loan perspective.
Note: You cannot create more than one mirror loan and you must have the "Create loan" role in the system.