About addgst.com
| Site | addgst.com |
|---|---|
| Operator | An independent publisher. addgst.com is not run by a government body. |
| Started | October 2026 |
| Contact | contact@addgst.com |
What the site is for
addgst.com gives quick, correct answers to the arithmetic around goods and services tax (GST): adding 10% GST to a price, taking GST out of a total, totalling the GST on a list of items, and estimating the GST part of a business activity statement (BAS). There is also a calculator for New Zealand’s 15% GST. The tools are free, need no sign-up and work on a phone.
The calculations run in your browser. What you type is not sent to our servers. See the privacy policy.
Where the information comes from
Every rate, threshold, rule and label on this site comes from the official pages of the Australian Taxation Office (ATO) or, for New Zealand, Inland Revenue. Each page lists its sources at the bottom and shows the date it was last updated. We check rates, thresholds and BAS labels, such as the 10% rate and the $75,000 registration threshold, against those sources when a page is published, and review them when the ATO or Inland Revenue announces a change.
We write for people who need a number and a short, accurate explanation of where it comes from. Where the ATO accepts more than one method, such as the two ways of rounding GST on an invoice, we say so instead of picking one as correct. Where we are describing a rule only in outline, the page links to the official page that has the detail.
How the numbers are checked
The calculators work in whole cents and round half a cent up. The maths is covered by automated tests, including rounding edge cases and every worked example printed on the pages: each example is computed by the same code the calculators use and checked against the figures in the text.
What addgst.com is not
- It is not affiliated with or endorsed by the ATO, Inland Revenue or any other government body.
- It does not provide tax advice or tax agent services. Results are estimates based on the figures you enter.
- It does not lodge anything for you. The BAS calculator is a worksheet, not a lodgement.
For your own tax affairs, contact the ATO or a registered tax or BAS agent (the Tax Practitioners Board register lists them).
Corrections
If a result, a rule or a source looks wrong, email contact@addgst.com with the page and the figures you used. Confirmed errors are corrected and the page’s “Last updated” date changes.
How the site is funded
The site is free to use. It may show advertising in future to cover its costs. Advertising would be kept separate from the calculators and would never change a result. The privacy policy would be updated before any advertising is added.
The tools
- GST calculator: Add 10% GST to a price or find the GST in a total.
- Reverse GST: Take GST out of a GST-inclusive price (divide by 11).
- Invoice GST: GST on a list of items, with GST-free lines and totals.
- BAS calculator: Estimate 1A, 1B and the net GST on your BAS.
- NZ GST: Add or remove 15% GST for New Zealand prices.
- How to calculate GST: Formulas, worked examples and spreadsheet formulas.