The Fairfax-Ipsos poll released yesterday showed 81 per cent of voters applauded the initiative and a sizeable 22 per cent intend using the accelerated depreciation provision also known as instant asset write-off.

That’s great news for the struggling Abbott government politically but not such great news for the deficit-riddled budget as the 22 per cent take-up represents as much as a 19-fold increase of the estimated usage number in the budget.

Bank of America Merrill Lynch’s chief economist Saul Eslake said the poll findings suggested many voters may not understand the scheme and have assumed it to be both wider in its eligibility criteria and more generous, believing it would pay out on a dollar-for-dollar basis on new equipment purchases by small businesses.

Rather it is a tax deduction which, although it can be used on multiple sub-$20,000 item purchases, merely reduces the taxable income of a given business by $20,000 each time.

“I find it hard to believe 22 per cent of the adult population is eligible,” Mr Eslake said.

The respected economist said it was also of concern some people had heard the Treasurer’s invitation to get out and spend, and may be incorrectly assuming the Australian Taxation Office’s scrutiny of purported business-related purchases would be scant.

Already since last Tuesday’s budget, some creative marketers have been advertising their goods would qualify as legitimate commercial expenses, including art works, notwithstanding paintings are unlikely to qualify and would often be considered as appreciating investments — the very opposite of a depreciating asset.

“A lot of people will be disappointed when they go to their accountant and discover they can’t claim it, or when they get a visit from the tax office at some stage,” Mr Eslake said.

ReachTel pollster James Stewart echoed those concerns, arguing many people probably heard the words “cash” and “tax concession” when asked and simply answered in the affirmative.

He said many of these respondents may not even be eligible for the write-off.

“I would suggest there would be a portion of that 22 per cent who are apprentices for example, not understanding that just because they have to buy tools etc, that they could get the concession,” he said.

“One of the first questions really is are you eligible to claim, are you a small business owner, before you get to the question of will you claim.”

Mr Eslake said budget papers assumed the cost of the accelerated depreciation to be about $1 billion a year for the two years of its life.

He said assuming the highest rate of deduction — at the full 30 per cent company tax rate — and the highest allowable value per item of $20,000, that would mean a per-claim cost to the budget of $6000 — or a net additional cost $4800 given the instant depreciation rate supersedes the existing staged rate for which there are already costs.

Mr Eslake said figuring suggested the government was banking on about 208,000 claims, well below the potential two million to four million claims that could be made if 22 per cent of the 18 million strong adult population applies.

“It would make a very big hole in the budget if that were accurate,” Mr Eslake said.

A spokesman for Mr Hockey said the small business population was “just over two million” rather than 18 million.

He said the costing drew on “the total value of asset purchases recorded in tax returns and is not based on the number of assets”.

“The costing incorporates significant incentive effects and bring forward effects — that is, that businesses will make purchases earlier to take advantage of the $20,000 cap,” he said.