Upgraded sales and purchases that contain inventoried items can't be edited

Please note that sales and purchases that include inventoried items entered in a previous MYOB product cannot be edited or deleted in MYOB AccountEdge Version 3 after you upgrade. If you need to change one of these transactions, you must first reverse the transaction and then re-enter it with the correct information. This is necessary to ensure the integrity of your item history information in MYOB AccountEdge Version 3.

See What are changeable and unchangeable transactions? for more information about reversing transactions.