SAP Message /BEV1/EMC291 - Existing invoice document & cannot be changed, due to &&&

Diagnosis
The specified document is already saved and the empty balances updated.You want to change the document at a later date. Fields that areaffected by this change are those that affect empties tables. However,you cannot correct empties balances at a later date.

System Response
The system refuses to post the document.

Procedure
You can cancel the complete document and can create a completely newinvoice with all the relevant changes.