The Inland Revenue Department says a 10-year project to overhaul its IT infrastructure and introduce new processes to make it easier for taxpayers is still tracking below budget.
Treasury documents released yesterday showed the total cost of the project may be as much as $2.61 billion, when depreciation, capital charges and inflation adjustment are included.
IRD says these figures "have always been indicated in any reports to government", although they have not been included in public discussion of the estimated cost.
Excluding them, IRD estimates the total cost of $1.6 billion and $1.8 billion, of which the government is stumping up $1 billion and the balance coming from the tax department's existing reserves.
"The project is continuing to track on plan and is currently underspending against the budget approved by government," IRD said in an emailed statement.