The government plans to introduce a new tax on goods and services bought online.
The amount of GST not collected through online buying is valued at about $180 million a year.
Revenue Minister Todd McClay said overseas suppliers should not get an advantage over local businesses.
The law change would apply GST to items such as e-books, music videos and software purchased from overseas websites.
Offshore suppliers would have to register and return GST when their supplies of remote services to New Zealand residents exceeded $60,000 a year, Mr McClay said.