The rate
The standard rate in Australia is 10%. Some goods and services carry reduced or zero rates and others are exempt. The difference matters: zero-rated sales still let you reclaim the tax on your purchases, exempt sales do not.
Who must register
GST registration is compulsory once GST turnover reaches $75,000 ($150,000 for non-profits). Turnover is irrelevant in two cases: ride-share and taxi drivers must register from the first dollar, and so must anyone claiming fuel tax credits.
How to register
A business with an ABN registers for GST online through ATO online services for business; the alternatives are phoning the ATO on 13 28 66 or using a registered tax agent. Registration is compulsory once GST turnover reaches the threshold, and the business must register within 21 days of becoming aware that turnover will go over it.
After registering, the business collects 10% GST on taxable sales, claims GST credits on business purchases, issues tax invoices and lodges activity statements. These duties continue even if turnover later falls below the threshold, so registration should be treated as ongoing.
Filing and paying
Registered and filed with Australian Taxation Office (ATO).
Business Activity Statements quarterly for most, due the 28th of the month after the quarter, except the December quarter, which is due 28 February; monthly at $20 million or more of GST turnover, due the 21st. A registered agent buys more time.