NZ GST calculator: add or remove GST, estimate the return, and see what provisional tax is coming.
Add 15% GST to a quote or take it out of a receipt, estimate a GST return from your period’s sales and purchases, and work out provisional tax under the standard option from last year’s residual income tax, with the instalment dates. Rules as published by Inland Revenue, checked 9 October 2026. Runs on the page; the Excel download has the same formulas. Free, no email required.
How do you calculate GST in NZ?
GST is 15%. To add it, multiply the GST-exclusive price by 0.15 (or by 1.15 for the total). To take it out of a GST-inclusive price, the GST is 3/23 of it (13.04%), not 15%, so $1,150 contains $150 of GST. A GST return is the GST you collected on sales less the GST on business purchases that carry taxable supply information; if the difference is negative, it is a refund. Registration is compulsory once turnover passes $60,000 in any 12 months. Provisional tax is separate: if the residual income tax on your last return was over $5,000, Inland Revenue expects this year’s tax in instalments. Under the standard option that is last year’s figure plus 5% (or the year before last plus 10%), paid in three instalments, or two if you file GST six-monthly. In 6,190 positive publicly posted reviews of NZ accounting and bookkeeping practices, proactive advice is praised in 42.2% and deadline reliability in only 3.1%. The bill is never the surprise. The date is.
GST in, GST out, and the tax bill you can see coming.
Your numbers
Add or remove GST
GST return estimate
Provisional tax, standard option
What it works out to
Runs in your browser; nothing you type is stored or sent anywhere. The Excel download carries the same formulas, so the two always agree.
The job this document is doing.
- —GST was taken out of a receipt at 15% instead of 3/23, so every claim was overstated by about 2%
- —The quote said $4,000 and the customer assumed that included GST; the invoice said $4,600
- —Turnover crossed $60,000 in month nine and nobody noticed until the accountant did, a year later
- —The first provisional tax instalment landed on 28 August with nothing put aside, because last year’s tax had been paid in one lump
Open it and use it today.
- 01Add or remove GST: one amount, one switch, three figures (excl, GST, incl)
- 02GST return estimate: sales and purchases for the period in, GST collected, GST claimable and the amount to pay or refund out, plus the share of every sale to put aside and the $60,000 registration check
- 03Provisional tax, standard option: last year’s residual income tax in, this year’s provisional tax, the instalment amount and the due dates out (31 March balance date), with the $5,000 threshold applied
- 04Excel workbook with the same three sheets and formulas, and a how-to sheet
- 05Nothing you type is sent anywhere; the calculator runs in your browser
Free to use and adapt for your own business. An estimate for planning cash, not tax advice: your accountant files the return, and the estimation and AIM options may suit you better than the standard option.
The law behind it. Goods and Services Tax Act 1985 (15% rate; taxable supply information ss 19E to 19K; compulsory registration at $60,000, s 51) and Income Tax Act 2007 subpart RC (provisional tax: standard option uplift of 5% or 10%, $5,000 residual income tax threshold; instalment dates for a 31 March balance date 28 August, 15 January and 7 May, or 28 October and 7 May for six-monthly GST filers), as published by Inland Revenue. Checked on ird.govt.nz and legislation.govt.nz on 9 October 2026. A due date on a weekend or public holiday moves to the next working day.
Why this document, and not another one.
| Measure (NZ accounting and bookkeeping) | Figure | Rank among 11 praised traits |
|---|---|---|
| Proactive advice praised, positive reviews | 42.2% | 4th |
| Deadline reliability praised, positive reviews | 3.1% | 11th |
| Accessibility (easy to reach) praised | 42.5% | 3rd |
| Accuracy praised, positive reviews | 8.9% |
From 7,571 publicly posted customer reviews of 484 NZ accounting and bookkeeping practices, collected October 2026. Each review carries a single star rating: 4 or 5 stars counted as positive (n=6,190), 2 stars or fewer as negative (n=328, reported as rank order rather than precision, so negative-review figures are rounded). Praise and complaint traits were coded against a fixed taxonomy; no business is named. Trade figures on the invoice template page: transparent pricing is praised in about 23% of positive trade reviews and overcharging is the top complaint theme in negative ones. Full corpus, method and thresholds: the accounting & bookkeeping methodology page. Full findings: the accounting & bookkeeping research study.
Use it alongside
NZ tax and compliance deadline calendar 2026/27 (PDF and Excel)
GST, PAYE, FBT, provisional and terminal tax and return dates from April 2026 to March 2027, each shown with the working-day date it moves to when it falls on a weekend or public holiday, plus the first dates of 2027/28 and an Excel version with days-to-go flags.
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