​ATO claims no data was lost during HPE hardware two-day outage

The Australian Taxation Office (ATO) has issued a statement Wednesday morning, stating it did not lose "one petabyte" of data as a result of the two-day outage that plagued the agency this week.

"The petabyte of data referred to in media reports relates to storage capacity, which includes not only data but applications and systems as well," the ATO statement reads.

"This figure does not relate to data impacted by the outages."

The tax office admitted that it did experience "some" data corruption 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.

"No data has been lost," the ATO reaffirmed. "No taxpayer information has been compromised."

The ATO's website came back online overnight after the agency suffered a two-day outage to its online services, portals, and ato.gov.au website, caused by a "world first" hardware issue.

On Tuesday afternoon, the ATO called in external service provider 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.

According to ATO acting chief information officer Steve Hamilton, "specialist engineers" have been working through the night with ATO staff to rectify the outages.

"These outages relate to a new hardware storage solution that was upgraded in November 2015," Hamilton said in a statement on Tuesday. "Our primary backup systems, that should have kicked in immediately, were also affected."

While the ATO and HPE restored the agency's website, links from the website to other impacted systems were not fully operational and the ATO's Tax Agent Portal remained offline.

"Other services will be brought online gradually over the coming days and we will continue to keep the community informed of our progress," the ATO said. "We will work with any clients to ensure they are not disadvantaged because of the systems issues."

A report released on Tuesday by the inspector-general of taxation found tax practitioners had "met with significant difficulty in seeking compensation for losses" in relation to ATO system outages.

The report, stemming from a review into the taxpayers' charter and taxpayer protections, recommended the ATO provide internal review of compensation decisions where taxpayers can provide "new information or grounds which warrant the decision being reconsidered by a new and independent decision maker".

It also recommended ATO staff be trained in how to provide apologies, with the ATO agreeing to the recommendations in principle.

The ATO also confirmed on Wednesday that after the full restoration of its services, investigations into the cause of the outage will continue.