Jim Dawson, the international tax partner for Crowe Horwath based in Atlanta, Georgia, told the Otago Daily Times Mr Trump's opening salvo on tax was not likely to be where the final rates ended.
Mr Trump proposed slashing tax rates for businesses and on overseas corporate profits returned to the country in a plan his fellow Republicans generally welcomed.
What has so far not been included was Mr Trump's controversial ''border-adjustment'' tax on imports floated earlier by Republicans as a way of offsetting revenue losses resulting from tax cuts, Mr Dawson said.
A border tax would make companies exporting into the US less attractive to US purchasers and encourage US manufacturers to produce more, because of the tax benefits they would receive from Mr Trump's plan.
New Zealand's largest company, Fonterra, would be be affected and others were also in the firing line, he said.
In the US, the House Ways and Means Committee and the Senate Finance Committee each write tax law. Mr Trump had now indicated his starting position and the debate would continue from there.
Because the Republicans had control of all legislative branches of the US Government, it was likely the tax law would be much as Mr Trump wanted.
By putting his proposals out in public, Mr Trump would avoid the risk of failing, as he did with Obamacare. This time, the votes would be ''lined up'' before the legislation went through the system, Mr Dawson said.
However, the 15% lowest tax rate for so-called pass-through businesses (known as look-through companies in New Zealand) was likely to be moved up as the debate continued.
Mr Trump would be accused of lowering the tax rate for his property-owning colleagues, and himself, because the current rate for property partnerships was 39.6%, he said.
The highest personal tax rate would be 33%, indicating Mr Trump was playing to his business audience. The theory was if businesses paid less tax, they invested in new jobs, and the tax cuts would become ''tax neutral''.
Mr Dawson said Mr Trump could not afford to lose tax revenue and add to the burgeoning US deficit.
Criticism emerged yesterday from some Republicans because Mr Trump lacked plans for raising new revenue and could potentially add billions of dollars to the deficit.
However, US fund managers soon warmed to Mr Trump and his plans ignited a rally on the US stock market.
The 15% tax rate for the pass-through businesses was billed as a winner for small businesses.
A manager whose fund earned $50 million a year now would be paying $19.8 million in taxes, or 39.6%. That could drop to as little as $7.5 million if the rate was cut to 15%.
