How GST Works — A Complete Guide to Goods and Services Tax

Blog › Finance · 8 min read · Published 2026-03-11

Understand GST calculation, CGST/SGST split, input tax credit, and how to add or remove GST from any price.

What Is GST?

Goods and Services Tax (GST) is a comprehensive, multi-stage, destination-based indirect tax levied on the supply of goods and services. Adopted by over 160 countries including India, Australia, Canada, and Singapore, GST replaces cascading taxes like VAT, excise, and service tax with a single unified system.

The fundamental principle behind GST is to tax value addition at each stage of the supply chain rather than the entire product value, eliminating the "tax on tax" problem that plagued older systems.

How GST Calculation Works

There are two primary GST calculations every business and consumer should understand:

GST Exclusive (Adding GST): Total = Base Price × (1 + Rate/100). Example: ₹1,000 at 18% → ₹1,000 × 1.18 = ₹1,180
GST Inclusive (Removing GST): Base Price = Inclusive Amount / (1 + Rate/100). Example: ₹1,180 at 18% → ₹1,180 / 1.18 = ₹1,000

For Indian intra-state transactions, the GST is split equally between Central GST (CGST) and State GST (SGST). Interstate transactions use Integrated GST (IGST) at the full rate.

GST Rate Slabs in India (2025)

India uses a four-tier GST structure designed to balance revenue with consumer affordability:

5% — Essential items: packaged food, economy hotel stays, rail tickets
12% — Processed food, business-class air travel, smartphones under ₹10,000
18% — Most goods and services: electronics, restaurants, professional services, software
28% — Luxury and sin goods: cars, cement, aerated drinks, tobacco, five-star hotels

Some items like fresh vegetables, milk, and educational services are exempt from GST (0% rate).

Input Tax Credit (ITC)

One of GST's biggest advantages is Input Tax Credit — businesses can offset the GST paid on purchases against GST collected on sales. This eliminates double taxation and reduces the final consumer price.

Example: A retailer buys goods for ₹10,000 + ₹1,800 GST (18%) = ₹11,800. They sell for ₹15,000 + ₹2,700 GST. They only remit ₹2,700 - ₹1,800 = ₹900 to the government.

GST Around the World

Different countries implement GST/VAT at different rates: Australia (10%), New Zealand (15%), Canada (5% federal + provincial), Singapore (9% from 2024), UK VAT (20%), EU countries (17-27%). The global median rate is approximately 15%.

Common GST Mistakes to Avoid

Applying the wrong HSN/SAC code leading to incorrect rate
Not claiming eligible Input Tax Credit
Late filing penalties (18% per annum interest in India)
Mixing up CGST/SGST with IGST for interstate vs intrastate

FAQ

Is GST the same as VAT?

Functionally similar — both are consumption taxes on value addition. GST typically replaces multiple indirect taxes with one unified system. In India, GST replaced 17 different taxes in 2017.

Who needs to register for GST in India?

Businesses with annual turnover above ₹40 lakh (₹20 lakh for services/special category states). E-commerce operators must register regardless of turnover.