​ATO website down following planned maintenance

The Australian Taxation Office (ATO) has experienced yet another outage, with its ato.gov.au website currently unavailable.

In response to the outage, the ATO issued an apology via a Twitter reply on Wednesday morning that did not point to the cause of the website being down.

"We're investigating current issues with our website as a priority," the ATO said in a Tweet. "We apologise for the inconvenience."

The apology follows planned maintenance the ATO announced last week, which was scheduled to be performed over the four-day Easter long weekend.

Wednesday's outage follows a run of issues that have been plaguing the tax office since late last year.

In early February the ATO recovered from an "unforeseen complexity" during a system restoration that left its core platforms offline.

The ATO had reported three days prior that it had suffered another setback to its systems restoration and had called in Hewlett Packard Enterprise (HPE) technicians to work on restoring its systems and online services.

HPE upgraded the ATO's hardware back in 2015, which is "basically the same" hardware used by other large clients of the IT giant.

The ATO's website, tax agent, and business portals initially crashed on December 12. The outage continued through to December 13, when the ATO first called in 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.

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

At the same time, the ATO claimed almost everything was back up and running, but did admit that "some" data corruption was experienced as a result of the incident, and noted it was in the process of having the data fully restored from a back-up.

On December 20 -- more than a week after the initial hardware failure -- the ATO said it was still experiencing reduced functionality across some of its systems.

"What compounded the problem beyond the initial failure was the subsequent failure of our back-up arrangements to work as planned," Jordan explained previously. "The failure of our back-up arrangements meant that restoration and resumption of data and services has been very complex and time-consuming."

The tax office's systems fell over again on February 2, 2017, with the outage affecting all of its online services, including the ato.gov.au website.

The ATO has also appointed PwC to conduct an independent review into the long-running incident. The tax office expected the consultancy firm's review to provide insight into what actually happened and why, and what needs to be done to ensure the same incident does not occur in the future.