How to calculate Goods and Services Tax for New Zealand
To find the cost including GST, multiply the amount exclusive of GST by 1.15.
Example: $100.00 * 1.15 = $115.00
To calculate GST component, multiply your GST-inclusive amount by 3 then divide by 23.
Example: GST-inclusinve cost is $200.00. GST component is 200 * 3 / 23 = $26.09