sold_to_site_use_id is null on the order header for some orders

Hello All,

Can anybody tell me when can the sold_to_site_use_id on order header id be null ? I have seen some orders where it is null but majority orders have it as some value.

due to this orders are not picked in one report. the sold_to_site_use_id is there on the customer record for orders missing it on their headers.

Please let me know if anyone has an answer ?

thanks in advance to all.