There are a small number of supplies that are GST free. If you make a GST free supply, you cannot charge GST but you can claim back all your GST paid.

GST supplies include:

Health and Medical Care
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Services by medical practitioners and pathologists;
Services by allied health practitioners such as physiotherapists, naturopaths, nurses and optometrists;
Hospital treatment;
Disability services;
Medical aids and appliances;
Pharmaceuticals;
Health insurance.
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Educational Supplies and Childcare
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School and university fees
Certain coarse materials
Student accommodation
Professional and trade courses
Approved childcare
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Fresh Food and Beverages
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food and ingredients for food for human consumption
beverages for human consumption and ingredients for such beverages
goods to be mixed with or added to food for human consumption (including condiments, spicings, seasonings, sweetening agents or flavourings)
fats and oils marketed for culinary purposes
any combination of any of the above
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Items specifically excluded from the definition of food are:
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live animals, except crustations and molluscs
unprocessed cows milk
unprocessed or untreated grain, cereal or sugar cane which is unchanged in form, nature or condition
cultivated plants that can be consumed as food for humans without processing or treatment
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In effect, the exclusions mean that food will not generally be excluded from the GST until they have been processed or treated in some way. So sale of products by primary producers to processers or treaters will be subject to GST.

Other GST-Free Supplies
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Sale of a “going concern”
a grant of crown land
certain sales of farm land
water, sewerage and drainage;
cars for disabled people
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