Free tool
GST Calculator NZ
Add or remove 15% GST from any amount, with results as you type, ready to copy.
GST exclusive (net)
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GST (15%)
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GST inclusive (total)
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Standard 15% GST applies to sales within New Zealand.
This calculator uses NZ's standard 15% GST rate and is general information, not tax advice. Some supplies are zero-rated or exempt, check with IRD or your accountant for your situation.
15%
NZ's GST rate on most goods and services.
× 1.15
to add GST to a GST-exclusive price.
× 3 ÷ 23
to find the GST inside a GST-inclusive price.
The maths
How to calculate GST in NZ (the actual maths)
Adding GST. GST in New Zealand is 15%. To add it to a GST-exclusive price, multiply by 1.15. Quoting a client $2,400 for a job? The invoice total is $2,400 × 1.15 = $2,760, of which $360 is GST.
Removing GST (the 3/23 trick). Going backwards is where people slip up. The GST inside a GST-inclusive price is NOT 15% of that price. It's 3/23 of it. A $920 GST-inclusive invoice contains $920 × 3 ÷ 23 = $120 of GST, making the exclusive amount $800. (Check: $800 × 1.15 = $920.) If you take 15% of $920 you get $138, which is wrong, and that error shows up in real GST returns more often than IRD would like.
Why 3/23? Because 15% of the exclusive amount equals 15/115 of the inclusive amount, and 15/115 simplifies to 3/23. That's it. No magic, just a fraction.
GST-inclusive vs GST-exclusive
Consumer prices in NZ are almost always shown GST-inclusive, so the shelf price is what you pay. Business-to-business quotes are often GST-exclusive, marked "+ GST". When you're quoting, say which one you mean; the difference on a $10,000 job is $1,500, which is an awkward conversation to have after the invoice goes out.
The $60,000 registration threshold
You must register for GST when your turnover passes $60,000 in any 12-month period, or when you expect it to in the next 12 months. That's turnover (total sales), not profit, and the 12 months are rolling, not the tax year. Side hustles cross it without noticing: $5,000 a month of Shopify sales is $60,000 a year, and the obligation starts when you cross, not when you notice. You can also register voluntarily below the threshold, which is worth discussing with an accountant if you have big input costs.
Once you're registered
You add 15% GST to your taxable sales, claim back the GST on business purchases, and file returns on your cycle: monthly, two-monthly (the common default) or six-monthly. The return is essentially "GST collected minus GST paid"; the hard part is having clean records of both. (Foreshadowing: that's the next section.)
SortMe Pro
The calculation is the easy part. The records are the problem.
A one-off calculation is what this page is for. If you're a sole trader or run a side hustle, the harder job is arriving at return time with records you can actually stand behind, rather than a spreadsheet and a folder of screenshots.
SortMe Pro keeps those records straight through the year. Your business gets its own books beside your personal money, every transaction is categorised as it lands, deductibles get tagged in the moment, and $500+ spends prompt a receipt photo. At end of financial year your accountant gets it all in one click, in the format they asked for.
SortMe doesn't calculate or file your GST, and it won't pretend to. That stays with you and your accountant. What it removes is the evening you'd otherwise spend rebuilding the year from bank statements.
Recommended by accountants and bookkeepers. SortMe Pro is $49/month or $299/year, unlimited entities.
