GST (Goods and Services Tax) is a unified indirect tax levied on the supply of goods and services across India. It replaced multiple taxes like VAT, service tax, and excise duty. GST has five slabs: 0%, 5%, 12%, 18%, and 28%, applied based on the type of good or service.

India has four main GST slabs: 5% (essential goods like packaged food, medicines), 12% (processed food, business class air tickets), 18% (most goods and services like electronics, restaurants), and 28% (luxury items like cars, tobacco, aerated drinks). Some items like fresh vegetables, milk, and eggs are exempt (0%).

CGST (Central GST) and SGST (State GST) are levied on intra-state transactions and are split equally between the Centre and State. IGST (Integrated GST) is levied on inter-state transactions and imports, collected entirely by the Centre. For example, an 18% GST within Maharashtra = 9% CGST + 9% SGST.

To add GST: GST Amount = Original Price × GST Rate / 100. Total Price = Original Price + GST Amount. To remove GST from an inclusive price: Original Price = Inclusive Price × 100 / (100 + GST Rate). GST Amount = Inclusive Price − Original Price.

GST registration is mandatory if your annual turnover exceeds ₹40 lakh for goods (₹20 lakh for services, ₹10 lakh for North-Eastern states). It is also mandatory for interstate suppliers, e-commerce operators, and those making taxable supplies regardless of turnover.

The composition scheme is for small businesses with turnover up to ₹1.5 crore (₹75 lakh for services). They pay a flat tax rate (1% for manufacturers, 5% for restaurants, 6% for services) instead of regular GST slabs and file quarterly returns instead of monthly.