However, Deloitte tax partner Allan Bullot said retailers should not get their hopes up yet.
"Online shopping, as it becomes more and more important to the New Zealand economy, is going to put more pressure on GST, at some stage it will need to be fixed," Bullot said. "It's just the timing - whether it's now or in a while."
There were different issues around taxing the online sales for goods compared with services, he said.
"The GST regime for bringing goods into the country, that could be changed tomorrow by the Government and wouldn't require any law change," he said. "Every import you have is subject to GST, it's just that Customs exercises their discretion not to collect it where the amount of GST is so small."
Currently, taxes are collected on imports where GST and other taxes total $60 or more.
When goods arrive at the border valued above the threshold price, duty, GST and the flat charge covering entry into New Zealand and a biosecurity levy, is calculated and a letter outlining the charges is sent to the person. The parcel is then held until the fee is paid.
Bullot said this could be changed anytime and the Government could simply lower the threshold price at which GST was applied without requiring a law change.
"It would be appallingly difficult to implement," Bullot said.
"From an operational perspective it's a much bigger change than a lot of people think, and you then have to ask, do we want Customs to be protecting our borders - stopping drugs and fruit flies coming into the country - or do we want Customs to be collecting GST on a $20 book that's coming into the country."
To implement such a system would require a big increase in the number of Customs staff, and the current method of tax collection would be far too inefficient, Bullot said.
Even if customers did not mind paying the tax, the time delay while they paid and waited for it to clear would be a considerable deterrent, he said.
"When you start dropping [the tax threshold] down into the lower values, you need a lot more orders to get the same collection of GST, and it comes down to the fact that you don't want to have a collection mechanism that costs more to collect the tax, than it is collecting."
Bullot said this would also raise issues about whether duty free should be taxed and whether tax refunds in other countries should be continued.
There were examples where countries had managed to make systems work, but these tended to be extreme, he said.
In Australia, the current threshold is A$1000, which is the highest in the OECD, compared with Canada which applies tax to any overseas online purchase over $20.
Australia has previously looked into dropping the threshold but had decided the revenue collected would not be worth the effort. However Key said this would become more of an issue as online shopping continued to increase.
It would be more difficult to implement GST on services because there was no physical product to track, Bullot said.
The Government had investigated using the US method of self-assessment, where individuals calculated the GST and tax owed and made a return at the end of the year, but had concluded this was too difficult.
Bullot said the best approach for New Zealand was to wait for the outcome of an OECD investigation into ways to implement tax for online sales, although this had been underway for some time and was not likely to result in a solution in the near future.
