​ATO warns of another outage as it moves to repair last year's 'unprecedented' hardware failure

​The tax office has said users of its online systems can expect disruptions as it seeks to fix the hardware problems lingering from late last year.

The Australian Taxation Office (ATO) has said it is expecting disruptions to its online systems as it looks to fix the problems that emerged last year, when the ATO experienced a "world first" hardware issue.

According to AAP, a business reporting system known as SBR1 failed last Friday, but was resolved that afternoon, with an ATO spokeswoman describing the event as a "minor disruption".

"The complexity of the restoration means there is still work being done to return our services to normal. There may be some disruptions to service as this work is undertaken," the spokeswoman said Thursday. "Information about our systems continues to be updated on the website and through our social media channels."

The tax office took its systems offline to conduct a "critical system maintenance" last weekend as the agency sought to restore systems to full functionality.

It also undertook a significant amount of work over the Christmas break to ensure its website and portals were functioning properly.

The ATO's website, tax agent, and business portals initially crashed on December 12 as a result of a "world first" hardware issue. The outage continued through to December 13, 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.

Three days later, 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."

At the same time, the ATO said almost everything was back up and running, but did admit that "some" data corruption was experienced 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.

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

The storage hardware in question was upgraded in November 2015 by HPE and was seen by the ATO to be "state-of- the-art" at the time, with the ATO noting it is "basically the same" hardware used by other large clients of HPE.

"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."

With AAP