The Australian Taxation Office (ATO) has apologised for a serious problem with its technology which saw critical systems go offline for more than two days.

The ATO’s data storage systems crashed on Monday, taking down the agency’s website, tax agent portal and case management system.

While the systems are now slowly being restored, one of the world’s largest accounting bodies has called for the ATO to give extensions to people affected.

“The real issue is how quickly it’s all going to be back online and what that means for businesses that might have documents they needed to lodge, or payments they needed to make,” said Paul Drum, the head of policy CPA Australia which represents more than 100,000 certified practising accountants.

“We need to make sure that when the system is back up and running, that the ATO is going to be cutting some slack to those businesses to ensure that they’re not going to be fined for late lodgement or for late payment, as a consequence for the system failure at the ATO.”

The ATO started experiencing problems on Monday, after both its primary and back-up storage systems crashed.

As a result, data was corrupted and – after lengthy troubleshooting – had to be restored from other back-up sources.

“We will work with any client to ensure they are not disadvantaged as a result of the outage,” according to a statement on an ATO website.

“There has been no loss of data. No taxpayer information has been compromised.

“ATO experts and our partners at HPE [Hewlett Packard Enterprise] have continued to work around the clock to bring our core systems back online.”

The ATO’s affected hardware storage system was upgraded in November 2015.

Visitors to the ATO site were met with this message.

The tax office’s website was restored early on Tuesday evening, however “certain tools, calculators and our online services (such as the portals)” remain offline.

Mr Drum said the outage is not a good look.

“It’s certainly embarrassing for the ATO, but I also think it’s embarrassing on a broader level,” he said.

“Not long ago we had the issue with the census and IBM, and the government lost face over that.”

“I think some will be making a call on the government to say ‘are they resourcing the tax office properly to enable it to do its job?’.”

All services to resume in the ‘next few days’

The ATO said that while its website and case management systems are back online, it will be at least a few more days before all services resume.

“We are working towards bringing the Tax Agent Portal back online later today,” a spokesperson said.

The ATO said that the technology problems are not as a result of a “cyber attack” or a “denial of service”.

“After full restoration, investigations will continue on the cause of the outage to ensure we treat the underlying issue,” the spokesperson said.

Mr Drum said many CPA Australia’s members remain concerned.

“Our members rely on these systems and the ATO to be able to do their job and provide services to their clients, and at the moment their hands are tied.”

-ABC