GST.co.nz · Independent · Since 2019

New Zealand's dedicated GST resource.

The definitive source for free, accurate GST calculators and guides. Whether you're adding 15% to an invoice, filing a return, or navigating GST on a property transaction, GST.co.nz has the tool you need. All updated for the 2026/27 tax year.

GST.co.nz is New Zealand's most comprehensive dedicated GST resource, bringing together 20 purpose-built calculators and 10 in-depth guides covering every aspect of the Goods and Services Tax. From the straightforward task of adding or removing 15% GST to the complexities of property transactions, mixed-use asset apportionment, and the marketplace rules for imported digital services, this platform provides accurate, IRD-compliant tools completely free of charge.

The GST calculator handles the three core operations every New Zealand business and consumer needs: adding 15% GST to a GST-exclusive amount, removing GST from a GST-inclusive total, and extracting the GST content using the IRD-prescribed 3/23 fraction method. The reverse GST calculator focuses specifically on working backwards from a total to find the pre-GST amount and the GST component, with support for historical rates and the Australian 10% rate for trans-Tasman businesses.

For businesses navigating the registration process, the GST registration threshold checker determines whether your turnover has exceeded (or is likely to exceed) the $60,000 rolling 12-month threshold that triggers compulsory registration. The GST for tradies calculator is built specifically for the construction and trades sector, handling progress payments, retentions, and the practical realities of GST on building projects.

Advanced tools include the GST return estimator, which mirrors the GST101A return format so you can preview your GST position before filing. The GST on property transactions calculator navigates the compulsory zero-rating rules under s 11(1)(mb), going concern treatment, and the nominee and bare trust provisions that catch many property buyers and sellers. The GST penalty and interest calculator computes the full cost of late filing or late payment, including the initial 1% penalty, the 4% penalty at day 7, the 1% monthly incremental penalty, and use-of-money interest at the current IRD rates.

GST.co.nz is part of the Calculate.co.nz group, New Zealand's largest collection of free financial calculators. For PAYE, mortgage, KiwiSaver, FIF, FBT, and 200+ other calculators, visit Calculate.co.nz.