Would it not be better practice for the purchase and sales orders to use the nominal codes for the relevant stock item rather than use the defaults against the customer / supplier? We are a multi-disciplined company with several departments and it is not practicable to have a different customer / supplier code for each part of the business. We would prefer to see the sales / purchase orders collect and process the information from the nominal code / product group rather than defaulting it to the customers suppliers code where it is giving all extra work to correct this.,
If your using Sage 200 Professional, you can choose if the codes come from customer or stock its within SOP Settings > Default accounts tab > use same nominal code as 'stock item revenue account'
If you are on Sage for Education and your data was migrated, then it could be that this setting wasn't set correctly.