the matthew kidman view on asz , page-8

devsadv - My understanding is that this was an abnormal write back to profit, due to acquisitions not performing as well as anticipated. At the time of purchase, some of the agreed price was deferred, subject to future business performance. Because the business performed worse than expected, the deferred consideration was not required to be paid to the vendors - hence the write back to profit.
You are right - this should have been highlighted, as it was clearly not part of normal earnings. For me, this showed a lack of transparency from management, and coupled with a few other suspect things in the profit announcement, led me to sell my holding, as I no longer had faith in management.