Once an invoice has been completed for a Sales Order, the Sales Order cannot be deleted. You may remove any order lines or quantities that have not been included on the completed invoice but the Sales Order may only be closed when the invoiced quantity is also dispatched within Unleashed. 

The reason for this is that the financial side of the Sales Order has been completed and passed to your accounting provider and cannot be reversed, therefore the stock must also be updated (dispatched) to match. 

How to manage a Sales Order that is invoiced but cannot be dispatched

When there is not enough stock available to dispatch the invoiced quantity on a Sales Order, you will need to increase the outstanding product's stock on hand quantity by either:

• Completing a Stock Adjustment for the invoiced product.
• Receipting a Purchase Order for the invoiced quantity.
• Assembling the invoiced quantity.

Once there is enough stock on hand available, you can dispatch (ship) the invoiced quantity and complete the Sales Order. 

At this point, your stock on hand will be reduced back to it's original quantity and you can then complete a Credit Note to return the invoiced revenue and balance your sales reporting. 

For more details, see the below helpfile links:

Add Stock Adjustments

Create and manage Shipments

Add a Credit Note