Cannot delete an invoice as a new functionality?

 Hi,

We have recently upgraded to 11.5.10.2. and we need your experience because we're experience problems with "new functionality".

Users cannot delete invoices. They create an invoice and validate it. Once the invoice is validated, they cannot delete it.

Oracle says:

Any invoice which has a validated distribution cannot be deleted after 11.5.9 due to the new SLA architecture.  Since cancelling an invoice automatically submits validation, the cancelled invoice cannot be  deleted.

Ok, invoice is not posted and it's not paid, so we cannot understand where is the problem with SLA architecture.

Is there any way to delete invoices as we could do in our previous version.