It costs an average of $611 every time someone makes a complaint to the Australian Tax Office, the national auditor has estimated.
Dealing with 26,431 grievances - more than 60 per cent of which were upheld - cost the tax office $16.2 million last financial year.
The federal government's top revenue collection agency has the equivalent of 180 full-time staff dealing directly with taxpayer gripes, many of which relate to refund delays and other processing dramas.
In its report tabled in parliament, the Australian National Audit Office (ANAO) also said tax office staff were asking for too many extensions to deal with complaints and found the privacy of staff with complaints made about them were not well enough protected.
When it came to the cost of complaints the auditor included the salary, superannuation, long service leave and training expenses of staff who worked in complaints handling.
It took into account receiving and recording complaints as well as support activities such as quality assurance reviews and the investigation of system-wide flaws.
The $611 figure does not take into account indirect management, administration or corporate support expenses.
The cost fell to $382 per complaint when support functions – such as quality assurance reporting and investigations into systemic problems – were excluded from the calculation.
“Having a good understanding of the cost of handling complaints not only assists agencies in allocating resources to efficiently handle complaints, but also helps them to appreciate the resources that could be otherwise deployed by preventing complaints,” the ANAO report said.
The report said tax office staff had been needlessly telling people it needed to extend the timeframe to deal with their complaints beyond the 21-day deadline the agency sets for itself.
Almost 40 per cent of the claims with extended timeframes were finalised within 10 days.
“This was indicative of a tendency on the part of some ATO staff to routinely extend timeframes,” the report said.
“Such extensions should only be arranged when there is a clear need for an extension.”
Meanwhile, there was no way for the ATO to check whether officers had been accessing files relating to complaints made about themselves - a flaw the office agreed to fix.
There had also been cases where the privacy of ATO officers or taxpayers had not been well enough protected when complaints were filed.
To protect their privacy, procedures require the names of ATO officers to be included in the initial complaint record but to minimise the incidence of identifying them in other records which might be seen by other staff.
"Notwithstanding this policy, the ANAO identified 12 instances out of 20 named officer complaints sampled where the name of the ATO officer, and details of the investigations, were included in linked activities on complaints records," the report said.
In some instances, documents included sensitive information about taxpayers as well as ATO officers.
The ATO, which has done a lot of work recently to lower complaints, has agreed to put in place tougher restrictions restricts for internal systems dealing with complaints.
The number of grievances submitted to the ATO last financial year was 36 per cent lower than the average over recent years which sits at 42,000.
The decrease saved taxpayers more than $9 million.