The Australian Taxation Office (ATO) website and online services are down for the second day in a row after a hardware failure on Monday.
"We worked hard overnight to resolve issues but systems remain offline," the ATO said via Twitter on Tuesday morning. "We aim to roll out services during the day & provide an update soon."
The ATO announced on Twitter just before 9.30am AEDT on Monday that its services were down.
"We're investigating issues with our online services, portals, and our website as a priority," the office said. "Apologies for the inconvenience. Stay tuned for details."
A spokesperson for the ATO told AAP that no taxpayer information has been compromised.
It is understood the problems stem from "hardware issues" and not caused by any external factors.
"All available resources are working to resolve these issues as a priority," the spokesperson said.
On Monday afternoon, the ATO advised specialist staff were still working to resolve issues.
"Services will remain offline while staff work through the night on a fix. We'll update you again in the morning. Thanks for your patience," the ATO announced via Twitter.
The office said it was working towards having systems back up on Tuesday; however, at time of publication the website was still down.
The ATO ran two days of scheduled maintenance earlier this month during which the system was taken down.
In 2010, the tax office selected Hewlett-Packard Enterprise Services a preferred tenderer for its centralised computing bundle, beating out IBM to the deal.
At the time, the centralised computing contract was set to include the provision and support services for mainframe, midrange data warehouse, storage, and secure gateway, as well as data centre facilities, networks, and management.
The following August, the ATO appointed HP Enterprise Services Australia, IBM Australia, Accenture Australia, Capgemini Australia, and CSC Australia to a panel of vendors to provide the department with application development.
The length of the standing offer agreement was three years, with two one-year extension options attached, stretching the possible contract length out to 2016.
Taxpayers in Australia that missed the October 31 deadline for lodging their return were given a 24-hour extension, after the federal government's myGov website suffered a 10-minute glitch at the end of October.
Department of Human Services general manager Hank Jongen confirmed that services run by the department, including myGov, were affected by a "short disruption".
As a result of the 10-minute delay, the ATO extended the deadline for lodging a tax return.
In November last year, the ATO released its Digital by default consultation paper that called for feedback from taxpayers, as part of proposed changes to improve the public's digital experience with the agency.
In the 2015-16 Federal Budget, the federal government announced its intention to spend AU$130.9 million over four years to deliver an improved experience for taxpayers. This included delivering future administrative savings and reducing red tape for superannuation funds and individuals by removing redundant report obligations, and by streamlining lost and unclaimed streamlined superannuation administrative arrangements.
Deputy commissioner Michelle Crosby said the Digital by default initiative will require most taxpayers to use ATO digital services to send and receive information and payments, except where they do not have the ability to do so, and will also mean those who still use paper products will need to make the switch.
"More and more, people are carrying out their day-to-day business online and in the last couple of years a focus of ours has been to make sure our digital services meet the community's needs. The Digital by default initiative is an extension of this commitment," she said at the time.
"For most people, it just makes more sense to use our online products, which offer a more personalised and convenient service."