You must register for GST if you carry out a taxable activity and your turnover was $60,000 or more in the last 12 months (or will be $60,000 or more in the next 12 months), or if GST is included in your prices.
You can only charge GST on your sales and income and claim it back on purchases and expenses if you're GST registered.
This video gives you a quick overview of registering for GST, including who should register and what to do when you are registered.
Flash video | 5:07 mins
If you're thinking about registering for GST, follow these steps: