How often must the vendor lodge GST returns to the Inland Revenue?

For the period from 1 December 2019 to 31 March 2020, non-resident suppliers of low value good that become liable to be registered between 1 December and 31 December 2019 will have a first return period of four months. After this transitional period, these suppliers will be required to file quarterly GST return beginning on 1 April 2020. More information: https://www.classic.ird.govt.nz/campaigns/2018/gst-policy-update.html