How to Calculate GST on Purchases and Sales

Calculating GST on purchases and sales in New Zealand is easy with a few simple formulas. Here’s how to do it.

Adding GST to a Sale

To add GST, multiply the base price by 1.15. For example, $100 becomes $115 with GST.

Removing GST from a Price

If you know the total price with GST, divide by 1.15 to find the original amount. For instance, $115 divided by 1.15 gives $100.

Knowing How Much GST You’re Paying

You can also find the GST portion by taking 15% of the base price. This helps you understand how much GST is part of the total.