The Australian Taxation Office says no taxpayer information has been compromised after a hardware failure brought down its website and online services.

However the website won't be back online until Tuesday.

The ATO announced on Twitter just before 9.30am AEDT on Monday 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."

An ATO spokesman told AAP no taxpayer information had 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 spokesman said.

On Monday afternoon, the ATO advised specialist staff were still working to resolve issues.

The office was working towards having systems back up on Tuesday,

Shadow assistant treasurer Andrew Leigh made light of the website problem on Twitter.

"I know the Turnbull Govt opposes tax transparency, but this is ridiculous," he tweeted.

The ATO ran two days of scheduled maintenance earlier this month during which time the system was taken down.

In November last year it released a consultation paper in which it flagged a shift to a digital-first strategy.