If there is an advice note that you no longer require, possibly because the stock was received in manually, the facility exists to permanently delete it.
To delete an advice note:
Warning: You cannot recover an advice note after it is deleted.
On the Advice notes tab of the Advice Note and Order Processing form, select the advice note (GRN) that you want to delete.
Do one of the following:
Right-click the advice note and select the Delete this GRN command from the shortcut menu.
Click the 
Delete the selected advice note toolbar button.
Select the Delete the selected advice note command from the I want to... menu.
The following message is displayed:
Are you sure you want to permanently delete the selected GRN?
Click Yes.
The advice note is deleted.