The Australian Tax Office was given $679 million in 2016 to run the task force over four years.

It was expected to raise an extra $3.7 billion in taxes by focusing on multinational companies, large groups and high-wealth individuals.

But in a report released on Monday, the auditor-general found while there had been a significant increase in compliance activity over the period, it was not clear how much money was raised as a result of the task force.

"Because the ATO had not implemented a methodology to clearly identify revenue arising from task force activities, it is not clear exactly how much of this increased revenue is a direct result of the task force," it said.

There is no stand-alone business unit within the ATO to support the task force's work.

There are no specific staff or cases dedicated to the task force.

The auditor-general found the ATO had no way of accurately monitoring task force resources.

As a consequence, the tax office could not demonstrate it had met its stated commitments.

The auditor-general recommended the ATO document the source and basis of each assumption used in its resourcing and revenues models, to which the tax office agreed.

However, the ATO disagreed with a recommendation to document how it would report and monitor the resourcing and revenues associated with task force funding.

It also disagreed with documenting the pre-existing levels of related resourcing and revenues.

The ATO did agree to develop a framework or set of principles to support the accurate monitoring of costs and revenues of its compliance measures.

In its response to the audit, the ATO said there were significant complexities involved in managing large budget measures such as the task force.

"Particularly when government funding extends existing resources that have been in place for a very long period of time, increases ATO resources to expand existing programs and undertake new work programs," it said.

The tax office said it was not possible, as the auditor office would have preferred, to separate task force-funded positions and casework from existing ATO resources.

"Whilst this approach might be appropriate for some specific funded measures, the same cannot be said for the task force," it said.

"Since its inception in 2016, it has been clear that the task force is not a separate program but a combination of effort across various business areas of the ATO to tackle tax avoidance."

Australian Associated Press