Free tool
NZ GST Calculator
Add 15% GST to a price, or work backwards from a GST-inclusive total. Built for tradies pricing jobs — no signup needed.
- Excluding GST
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- GST (15%)
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- Including GST
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The formulas (for doing it on paper)
| Add GST to a price | price × 1.15 | $400 × 1.15 = $460 |
| GST portion of a total | total × 3 ÷ 23 | $460 × 3 ÷ 23 = $60 |
| Remove GST from a total | total ÷ 1.15 | $460 ÷ 1.15 = $400 |
The common mistake: taking 15% offa GST-inclusive total. GST is 15% of the smaller (exclusive) number, so it is 13.04% of the total — that's why the backwards formula is ×3÷23, not ×0.15.
Adding GST — quick reference
| Price excl. GST | GST at 15% | Total incl. GST |
|---|---|---|
| $100 | $15.00 | $115.00 |
| $250 | $37.50 | $287.50 |
| $400 | $60.00 | $460.00 |
| $500 | $75.00 | $575.00 |
| $750 | $112.50 | $862.50 |
| $1,000 | $150.00 | $1,150.00 |
| $2,500 | $375.00 | $2,875.00 |
| $5,000 | $750.00 | $5,750.00 |
Working backwards — quick reference
| Total incl. GST | GST inside it | Price excl. GST |
|---|---|---|
| $115 | $15.00 | $100.00 |
| $500 | $65.22 | $434.78 |
| $1,000 | $130.43 | $869.57 |
| $2,000 | $260.87 | $1,739.13 |
| $5,000 | $652.17 | $4,347.83 |
This is the direction that catches people out. A $5,000 job paid in cash contains $652.17 of GST, not $750 — the $750 figure belongs to a $5,000 price with GST added on top.
Quoting: plus GST or including GST?
Both are legal. Which you use should depend on who is reading the quote.
| Homeowners | Show the GST-inclusive total as the headline number. A consumer reading "$4,000 + GST" will remember $4,000 and be unhappy at $4,600. Under the Fair Trading Act, prices presented to consumers should not be misleading — a big exclusive figure with GST in small print invites trouble. |
| Businesses and main contractors | Plus-GST pricing is the norm, because they claim the GST back and think in exclusive figures. Still label it clearly — "$4,000 + GST" rather than a bare number. |
Whichever you choose, be consistent between the quote and the invoice. Most disputes about GST are really disputes about a customer who thought the quoted number was the final number.
When you have to register
Registration becomes compulsory once your turnover passes $60,000 in any 12-month period, or once you start adding GST to your prices. The threshold is measured on a rolling 12 months, not a tax year, which is what catches people out after a busy run.
Below the threshold it is optional. If you mostly invoice other businesses, registering early is usually sensible — they claim the GST back so your price is effectively unchanged to them, and you start claiming GST on tools, materials and vehicle costs. If you mostly invoice homeowners, registering makes you 15% dearer overnight. There is more detail in our guide for non-registered businesses.
Related
- Tax invoice requirements in NZ — what your invoice must show once you charge GST
- NZ invoice template
- NZ quote template
Common questions
- What is the GST rate in New Zealand?
- GST in New Zealand is 15%. It has been 15% since 1 October 2010 (it was 12.5% before that).
- How do I add GST to a price?
- Multiply the GST-exclusive price by 1.15. For example, $400 + GST is $400 × 1.15 = $460.
- How do I work out GST backwards from a total?
- To find the GST inside a GST-inclusive price, multiply the total by 3 and divide by 23. For example, $460 × 3 ÷ 23 = $60 of GST, leaving $400 excluding GST. Dividing the total by 1.15 gives the GST-exclusive amount directly.
- Why is GST 3/23 of the total and not 15%?
- Because 15% is calculated on the smaller, GST-exclusive number. Once GST is added, the total is 115% of the original, so the GST portion is 15/115 of the total — which simplifies to 3/23, or about 13.04%. Taking 15% off a GST-inclusive figure always gives the wrong answer.
- How much GST is in $100?
- If $100 is the GST-inclusive total, it contains $13.04 of GST and $86.96 excluding GST. If $100 is the GST-exclusive price, GST is $15 and the total is $115.
- Do I have to charge GST?
- You must register for GST (and charge it) once your turnover is over $60,000 in any 12-month period, or if you add GST to your prices. Below that threshold registration is optional — many sole-trader tradies register anyway to claim GST back on tools and materials.
- Should my quotes show prices including or excluding GST?
- For consumers, showing GST-inclusive totals is the safest practice under the Fair Trading Act — hidden extras cause disputes. For commercial clients, plus-GST pricing is common. Either way, say clearly which one your quote is.
- Is GST charged on labour as well as materials?
- Yes. If you are GST registered, GST applies to the whole taxable supply — labour, materials, travel, disposal fees and any margin. There is no labour exemption in New Zealand.
- How do I round GST?
- Work to the cent and round normally. Rounding differences of a cent or two on an invoice are not a problem; what matters is that the GST shown matches the amounts on the invoice.