Definição
GST is a value-added-style consumption tax. In most countries that use the name GST, the mechanics are similar to VAT: businesses charge tax on sales, claim credits on purchases, and remit the net to the tax authority.
India's GST (introduced 2017) is the most complex implementation. It has four main slabs — 5%, 12%, 18%, 28% — plus 0% and exempt categories. For intra-state supplies the tax is split into CGST (central) and SGST (state). For inter-state supplies it's a single IGST. Registration is mandatory above ₹40 lakh of aggregate turnover (₹20 lakh for services in most states).
Australia's GST is a flat 10% on most goods and services, administered by the ATO. Registration is mandatory at A$75,000 turnover. Canada has a federal 5% GST, combined with provincial sales tax as HST in some provinces (13-15%). New Zealand applies 15% GST, Singapore 9%.
Key difference from VAT in terminology: India uses "HSN code" for goods and "SAC code" for services on invoices — a classification system that determines the applicable rate.