Suggestions:
1) Users have to define an item with no stock maintenance for service-related activity. For this an item(service) should be created with Stock Option as ‘0’ flag for Inventory control. 0 value is for ‘Not stock maintenance’.
2) A Sales order (SO) is an authorized order for an agent or department to an external customer to supply the service and maintenance work. All tax calculations and terms & conditions will be entered here.
3) Users have to use the despatch, a manual transaction to sell services from Sale orders.
4) i) Users have to reference Sales order no. All the details regarding that Sales order would be loaded. If not you can enter at the transaction level Sales order number field. ii) Customers will be displayed to whom the product has to be dispatched. It is picked from the Sales order. iii) All delivery and shipment details can be entered in despatch if not entered in Sales order. iv) In details, users will have to select manually or enter the Sales order line number here to get other details. v) Ordered Item will be displayed, the item ordered by the customer. It is picked from the Sales order. vi) Users then have to enter the quantity of the item(service) despatched. Users can finish and confirm the transaction.