An enormous increase in the number of promotion appeals lodged by tax office staff last financial year has led some public sector unions to question the integrity of the agency's promotion system.
The Merit Protection Commission, the body which oversees and determines promotion revues, received 1590 applications for promotion reviews in 2019-20.
Of those, 988 were received from the Australian Taxation Office. The agency with the next highest amount of applications was Services Australia (374), followed by Home Affairs (166) and Defence (12).
Only positions between APS1 and APS6 are eligible for for a promotion review and reviews can only be sought by ongoing public servants who applied for and were unsuccessful for the position.
Promotion reviews are conducted by an independent panel consisting of two members appointed by the Merit Protection Commissioner and one delegate from the relevant agency.
The Merit Protection Commission received 739 applications in November and December 2019 alone, representing a 293 per cent increase on the same period in 2018.
The commission's annual report shows that the vast majority of these applications, 559, were from the ATO after a large round of recruitment. In November/December 2018 the commission received only eight applications from the tax office.
Of the 988 applications made by staff at the tax office across the financial year, only three resulted in a varied decision where the applicant was promoted.
Australian Services Union taxation branch secretary Jeff Lapidos said the large number of promotion appeals was due to a loss of confidence in the promotion system used by the ATO.
"Any applicant considered competitive for any of a broad range of advertised jobs is placed in a single or flat merit pool," Mr Lapidos said.
"Each [ATO] delegate then goes shopping for the candidate considered most suitable for the job they have to fill. Many fear that delegates choose candidates they know, trust or like and reject candidates they do not like or know.
"The promotion system needs to be re-designed to incorporate the needs of staff so they can be confident in its operation."
A tax office spokesman said the agency had conducted significant recruitment to deliver government commitments related to the Black Economy program, which targets criminal activities, and the Tax Avoidance Taskforce.
"During 2019-20, the ATO received 80,000 applications and promoted 2,579 ATO employees," he said.
"While the Merit Protection Commission received 988 promotion review applications relating to ATO recruitment, only 565 promotion decisions were eligible for review.
"Of these only 3 outcomes were overturned representing 99.5% of APS1-6 promotions being upheld. There were no systemic issues found by the Merit Protection Commissioner regarding ATO recruitment processes."
CPSU deputy national secretary Beth Vincent-Pietsch also raised concerns about the ATO recruitment process in 2019, labelling it "flawed, unfair and inconsistent".
She said there was a long list of issues with the process, including conflicts of interest, technological issues relating to video interviews and a lack of consistency and opacity in the assessment process.
"A long list of issues combined with extensive delays in finalising the process led to mass distrust with the whole round," Ms Vincent-Pietsch said.
"While the ATO has come to the table on addressing some of these issues, our members are looking for more surety that future recruitment rounds won't contain so many disappointing and distressing surprises."
In surge in applications led to significant delays in the Merit Protection Commission finalising promotion reviews.
A spokeswoman for the commission said the increased applications meant 78.1 per cent of promotion reviews were completed within key performance targets, down from 95 per cent in the previous year.
However, the commission still met its overall target of finalising 75 per cent of reviews within set timeframes.