Customer Own Address ID for Multi site orders

Dear All,

I am doing the process of Multi Site Order, I want to know do I need to enter the Customer Own Address ID in internal customers as well? since we are already entering on external customer.

Also, the check on single occurrence is still coming on internal PO and internal CO, Is this because I have not entered customer Own Address ID for internal customer and internal supplier,. Please confirm.

Thanks

IFP