While WorkGuru allows you to dispatch and invoice a stock sale separately to suit your specific workflow requirements, the quickest way to finalise a stock sale is via the the complete sale option.
Once a stock sale has been approved and the client has received the products and you want to invoice them immediately, from an approved stock sales detail's page click Complete Sale.
This will combine the dispatch and approved invoice process by doing both immediately and updating the stock sale with the dispatch date and invoice reference. Add a payment to the approved invoice if required.