1. Enter in to the Product Record
2. Click on the Suppliers button (bottom right of screen)
3. Click on the Supplier you wish to set as Preferred
4. Check the tick box Preferred? at the bottom of the screen
5. Click Save


Preferred Supplier against multiple Products can be updated via the Grid Manager;


Go to Stock > Product Supplier Grid Manager
In the change tab search for the vendor e.g. SPR/Essendant and select Preferred Supplier - No Preferred Set and then hit search. The results tab will show all codes with no pref. vendor.
In the Change tab you will be able to update all these codes to your preferred vendor e.g. SPR/Essendant.

Please Note:  If the OWN supplier is showing against a sales order line, check the Supplier tab to see if any of the suppliers have a 'Y' in the 'Preferred' tab.

Products that do not have a preferred set will show the OWN supplier when the item is added to a sales order and will need to be updated so that a preferred supplier is set in the stock product record.