The website was still down at lunchtime on Wednesday.

A spokesperson urged people not to call, but to be patient.

"We are aware that people trying to lodge their tax return or an application for early release of super are currently experiencing issues with our systems," the spokesperson said. "We are investigating this as a priority, and our technicians are working to resolve the issue."

No details were provided about the number of people trying to access the superannuation lump sum and the numbers trying to lodge tax returns, nor why the website wasn't prepared for the influx.

To date, 2.4 million people have applied to remove up to $10,000 from their superannuation savings.

So far, $17.1 billion has been paid out.

The measures is one of the more controversial of the government's coronavirus responses, with suggestions that a sizeable proportion of people removing money are not in financial stress, that young people are depleting their superannuation, and that some people are spending the money on activities such as gambling.

The scheme has also been targeted by fraudsters.

The government allowed people to withdraw up to $10,000 before July 1 and another $10,000 from July 1. The average withdrawal in the first tranche was $7500.

Tax returns are also more lucrative this year, with a new tax deduction for working from home after offices were shut to hundreds of thousands of workers. People working from home can claim a straight 80 cents an hour as a tax deduction for the four months from March 1 to June 30. The deduction amounts to just over $500 for someone working full-time at home over those four months.

The government also found itself overwhelmed on March 23, when restaurants, pubs, movies and gyms were closed overnight, causing a rush on applications for the unemployment benefit. Centrelink queues stretched blocks of city streets, and the MyGov website crashed, a failure Government Services Minister Stuart Robert initially put down to a denial of service attack before admitting the claim had been wrong. The system designed for up to 55,000 users had been swamped by 95,000 trying to access it at once.

Labor assistant Treasury spokesman Andrew Leigh said it was "downright incompetent' that the government couldn't have the website fully functional for people wanting to lodge tax returns.

"When it comes to technology, as the Robodebt and Census failures have shown, the Liberals are as useless as a sunroof on a submarine," he said.