Small tools that get the cents right.

Who runs this

CalcGST is operated by Star Shop com, ABN 83 443 122 821, based in Melbourne, VIC. It is a small independent project, not a software company, and there is no sales team behind it.

You can reach a human at [email protected].

Why it exists

Most GST calculators are wrapped in advertising, ask you to sign up, or get the rounding subtly wrong. Most invoice tools are the free tier of an accounting subscription, designed to run out.

A sole trader who needs to send one correct invoice should not have to start a trial. These tools do that one job, properly, for nothing.

How the figures are calculated

Everything is worked in whole cents, never in decimal dollars. GST is applied once to the invoice total rather than to each line, which is what stops a long invoice drifting a cent away from its own total.

The arithmetic is covered by automated tests that run before every release, including the awkward cases — $10 including GST contains $0.91, leaving $9.09, and those add back to exactly $10.00.

Why nothing is uploaded

Amounts, ABNs, client names and line items are the kind of thing a business has every reason to keep to itself. Every calculation here runs in your own browser, so there is no server holding it and no breach that could expose it. You can confirm that in your browser’s Network tab.

Your business details for invoicing are stored in your browser’s local storage on that device, so you do not retype them. They never reach us. The privacy page sets out exactly what is kept.

What these tools will not do

• They do not give tax advice. Whether you must register for GST, or whether a particular sale is taxable, is a question for the ATO or a registered tax agent.
• They do not send invoices or track payments. That is what accounting software is for.
• They do not look up who owns an ABN. The ABN check verifies the number’s own check digits. The government register at abr.business.gov.au is the authority on ownership.

Other tools we run

We also run QR Generator AU — free QR codes for menus, WiFi, business cards and payment links. Same operator, same ABN, same approach: it runs in your browser and nothing you type is uploaded.

Where the rules come from

The GST rate, the divide-by-eleven method and the tax invoice field requirements all come from the ATO. Where this site summarises them it does so in plain English, and where a figure matters we say to check the ATO’s own guidance. Rules change; this site is maintained, but it is not the legislation.