From today, people will be paying more for online goods.
Offshore retailers selling products in New Zealand costing less than $1000 are now required to collect and pay GST.
The rule applies to businesses selling goods online in the country worth more than $60,000 annually.
The changes - announced in June by the Revenue Minister Stuart Nash - are intended to level the playing field for domestic retailers.
Mr Nash said all New Zealand businesses had long been required to collect GST, and now offshore retailers would have to as well.
Closing the tax loophole is expected to bring in roughly $130 million in revenue each year, by 2022.
According to Consumer NZ estimates the changes would mean products under $400 will become more expensive, while those valued between $400 and $1000 would cost consumers a little less.