The Australian Taxation Office was unable to measure and monitor the cost of a massive restructure or the savings achieved, an audit has found.
An auditor-general report tabled in parliament on Wednesday examined the agency restructure, known as Reinventing the ATO.
The audit found the ATO was unable to measure and monitor the total costs of implementing the program because of "low levels of conformance with requirements to track costs".
Out of 100 projects, only eight included actual costs in status reports and 13 projects included actual costs in closure reports.
As well, the ATO had not tracked the monetary savings associated with the program.
"However, in April 2017 it implemented internal reporting on financial benefits across the office, including Reinventing the ATO projects," the report said.
The auditor-general estimated savings ranging from $420 million to $599 million over the first five years of the program, with potential ongoing savings of up to $82 million a year after that period.
The ATO, which has been widely criticised in recent years especially in regard to the quality of its online services, said in response to the report the overall intent of the program was to "transform our internal culture" and provide a "stronger connection to the community".
"The ATO recognises this opportunity and is committed to continuous improvement in relation to project management," the agency said.
The ATO routinely deals with almost 11 million taxpayers and four million small businesses.
