Updating and Cancelling Sales Orders 
After you create a sales order, you can change all its data, provided that no target documents have been created based on it. Some of the possible changes include:
Delete, add, or duplicate rows
Update prices and discounts
Update quantities
Procedure
Cancelling Sales Orders
If the sales process has been interrupted and the sales order has not yet been drawn (fully or partially) to a target sales document, you can cancel it:
Choose
Sales – A/R
Sales Order 
and find the sales
order you want to cancel.In the menu bar, choose
Data
Cancel .The status Cancelled appears.
Closing Sales Orders
When the sales order has been partially copied to a higher level sales document, you can close it but you cannot cancel it.
Choose
Sales – A/R
Sales Order and find the sales
order you want to close.In the menu bar, choose
Data
Close .The status Closed appears.
Result
When you cancel or close a sales order for items, the quantity reserved for the customer is reduced by the quantity that appears in the cancelled or closed order.
A cancelled or closed sales order is not deleted. You can still display or duplicate it, but you cannot change it or copy it to a higher level sales document.
The system does not display cancelled or closed sales orders in the Open Items List report.