A member of the tax working group is warning the projected turnaround in the nation's accounts is heavily dependent on Treasury growth forecasts coming to fruition.
PwC chairman John Shewan says the bullish forecasts, tipping growth will pick up pace to 2.6 per cent in the year to March 31, 2013, rising to 3.4 per cent the following year, was something that had not been achieved since the early 2000s.
"We are surprised at the 29 per cent increase in tax and GST forecast over the next four years," he said.
"This is highly dependent on growth projections averaging three per cent over this period."
Mr Shewan said the Christchurch rebuild would have a big impact on growth.
Financial commentator Bernard Hickey said the rebuild, and continued growth in China and Australia, was being backed to get the economy and the government's finances back on track.
He said the Treasury forecasts were "rosy" but warned the downside scenario, on the back of a slowdown in China's economic growth and more speed humps on Europe's road to recovery, was more likely.
Mr Shewan said while a curb on government spending would help it meet targets, payments to pensioners were set to grow by 29 per cent over the next four years.
"The forecast hike in superannuation costs demonstrates the impact of the aging population. This is an elephant that will have to be addressed if we are to avoid inevitable hikes in taxes in the next few years," he said.