Goods and services tax, GST, is a tax on spending that works like VAT: businesses charge it on their sales, claim back what they paid on their purchases, and the final buyer carries the cost. The name is what differs, along with the rates and the rules about who must register.
In Canada the federal GST is 5% everywhere. Five provinces fold their own sales tax into it as a single harmonized sales tax, HST: 13% in Ontario, 14% in Nova Scotia and 15% in New Brunswick, Newfoundland and Labrador and Prince Edward Island, according to the Canada Revenue Agency. Elsewhere GST is charged alongside a separate provincial tax, such as Quebec's 9.975%. Canadian prices are normally shown before tax.
Australia charges 10% on most goods and services, and a business must register once its GST turnover reaches $75,000, according to business.gov.au. New Zealand charges 15%, per Inland Revenue. In both, prices to consumers include it, so an A$110 price is A$100 plus A$10 of GST.
India's GST is levied by both the centre and the states on the same base. A sale within one state carries central and state GST (CGST and SGST); a sale between states carries integrated GST (IGST), as the CBIC sets out. Rates vary by product.
For a registered seller, GST is money collected for the government, so margins should be worked on prices without it. The Amazon FBA calculator takes Australia's 10% out of the price before the referral fee when you are registered and leaves Canadian prices as shown. The Etsy fee calculator notes where Etsy adds GST or HST to its own fees if you have not given it a registration number.