If you are working as an independent contractor and will be in New Zealand for more than 183 days, and earning more than NZ$60,000.00 during this time, you will need to become GST (Goods and Services Tax) registered. New Zealand GST, similar to UK VAT, is currently set at 15% and is paid to the Government.
You can elect to submit GST returns to IRD on either a one-monthly, two-monthly or six-monthly basis. More information about GST can be found here.
There is no refund of GST available when you leave New Zealand. GST registered locums are, however, entitled to GST refunds on work related expenses such as a vehicle costs (or a percentage of these), petrol and work related telephone calls.
Once again, we strongly recommend that you obtain independent financial advice, especially if you will be paying your own income tax and GST.