You can choose how you want to fulfil your stock when processing orders in the Sale Order Processing and Stock Control modules.
Once this is set up you can maintain your individual stock items or product group fulfilment methods using Stock Order Fulfilment.
Open: Stock Control > Utilities > System Set Up > Stock Control Settings | SOP Fulfilment Methods.
This is the most commonly used type of processing, where a sales order is allocated and despatched from the free stock you hold.
Select this to use back-to-back sales order processing. This generates a purchase order directly from your sales orders if required.
Other tasks
Write off categories (stock settings)
Configurable names (stock settings)
Internal areas (stock settings)
Reference