When does my stock on hand decrease?

When stock on hand is calculated using shipment orders and receives:

The stock in hand for the items in your inventory increases when a Shipment Order is created for the items you deliver to your customers.

When stock on hand is calculated using Invoices and Bills:

The stock in hand for the items in your inventory decreases when an invoice is raised and sent to your customers. Invoices can be raised for sales orders in ‘Confirmed’ status or you can create an invoice directly and send them to your customers.