​ATO systems still not fully functional

The Australian Taxation Office (ATO) is still experiencing reduced functionality across some of its systems, more than a week after a storage hardware failure caused the crash of its online services.

"All business critical systems are live and performance is returning to normal as systems stabilise," the ATO said in a statement Tuesday evening.

The ATO's website, tax agent, and business portals initially crashed on Monday last week as a result of a "world first" hardware issue. The outage continued through Tuesday, when the ATO called in Hewlett Packard Enterprise (HPE) to help it determine the underlying cause of the problem that the ATO said was encountered for the first time anywhere in the world.

As of Tuesday evening, the Australian Business Register is currently available to users, but with reduced functionality. The tax office expects the full service to be restored in the "coming days".

Commissioner of Taxation Chris Jordan announced an independent review into the "unprecedented failure" on Friday and called it the ATO's worst unplanned system outage in recent memory.

"This was an extremely unusual and unfortunate event," he said in a statement. "The issues we have experienced this week do not relate to our overall IT capability or skills."

Almost everything was back up and running on Wednesday last week, when the tax office admitted that it did experience "some" data corruption -- not an entire petabyte, however -- as a result of the hardware-related incident, and noted it was in the process of having the data fully restored from a back-up.

"We are realistic that there may be some intermittent performance issues in the next couple of days as the full restoration process proceeds," the commissioner said Friday.

The ATO has reaffirmed throughout the aftermath that no taxpayer information has been compromised and that tax refunds owing will be paid before Christmas.

"We encourage lodgement and payment of the November monthly Business Activity Statement on time. However, anyone experiencing difficulties with lodging or making payments due to our system outages will not be subject to penalties, interest, or follow-up action providing lodgement and payment is made by 10 January 2017," the ATO said Tuesday.

"I will be doing everything I can to learn from what has happened this week and to put in place any necessary changes to minimise the risk of any recurrence," Jordan added. "Please be assured that I am committed to providing a quality, reliable, and contemporary service to the Australian community."