Commissioned on Australia Day the new $820 million computer system has so far sparked 17,000 public complaints, required more than 500 bug fixes and sent unintelligible data to Centrelink.

The Tax Office has now scaled back its new  computer system after it delayed 1 million tax returns, sent out return letters without cheques and failed to communicate with other computers.

Detailing a litany of mishaps the Second Commissioner, David Butler, has told a Senate estimates hearing that cost overruns and the new need to work on changes resulting from the Henry review meant the supercomputer would no longer become the ”integrated system for everything” originally planned.

The Tax Office will terminate its contract with Accenture to introduce the system and engage a separate consultant, CPT Global to advise on how to make it work during the coming tax season. It has employed an extra 330 staff in an effort to make the tax season work.