How to Remove GST from a Price (2026)

If a New Zealand price already includes the standard 15% GST, you cannot remove GST accurately by simply subtracting 15%. The correct method is to divide the GST-inclusive amount by 1.15.

Formula to remove GST in NZ

Price excluding GST = price including GST / 1.15

Then:

GST = price including GST – price excluding GST

Example: $345 including GST

GST-inclusive price: $345
Price before GST: $345 / 1.15 = $300
GST component: $345 – $300 = $45

Why you divide by 1.15

New Zealand GST is 15% of the pre-GST amount. A GST-inclusive price therefore represents 115% of the original amount. Dividing by 1.15 reverses the addition of GST.

Find only the GST component

If you already know the GST-inclusive price and only want the GST amount:

GST = GST-inclusive price x 3 / 23

For example, $1,150 x 3 / 23 = $150 GST, leaving $1,000 before GST.

Worked example: checking a stock purchase

A retailer in Hamilton buys stock for $4,600 including GST and wants the GST-exclusive cost for her books. Divide by 1.15: $4,600 / 1.15 = $4,000.00 before GST. The GST is $4,600 – $4,000 = $600.00.

She double-checks with the 3/23 shortcut: $4,600 x 3 / 23 = $600.00. Both methods agree, so she records $4,000 as the cost and $600 as the GST she can claim.

When you need to remove GST

Removing GST comes up whenever a price already includes it and you need the split:

Entering supplier invoices into your accounts at the GST-exclusive cost.
Working out how much GST you can claim back on a purchase.
Comparing a GST-inclusive shelf price with a GST-exclusive trade quote.

This only works where the whole price carries 15% GST. If part of the price is zero-rated or exempt, split those items out first.

More examples

Inclusive price	Before GST	GST
$115	$100	$15
$230	$200	$30
$345	$300	$45
$1,150	$1,000	$150
$2,300	$2,000	$300

Remove GST from price NZ FAQs

Why can’t I just subtract 15%?
Because 15% of the inclusive price is more than the GST inside it. For $115, subtracting 15% gives $97.75, which is wrong. The correct exclusive price is $100.

What is the 3/23 rule?
The GST inside an inclusive price is 15 parts in 115, which simplifies to 3/23. Multiply the inclusive price by 3/23 to get the GST directly.

Does this work for every price?
Only for prices that carry the standard 15% GST. It does not apply to zero-rated or exempt supplies.

What if a receipt mixes GST and GST-free items?
Remove GST line by line from the items that carry it, and leave the zero-rated or exempt items alone.

Remove GST manually or use the calculator

For a single amount, /1.15 is quick. For repeated calculations, use the New Zealand GST Calculator and choose the remove-GST option.

Related NZ GST tools

Official source

For current GST rules and transaction-specific requirements, check Inland Revenue.