GST formulas
Add GST: GST = Net × Rate ÷ 100, Total = Net + GST
Remove GST: Net = Total ÷ (1 + Rate ÷ 100), GST = Total − Net
CGST, SGST and IGST
GST on a sale within one state is split equally between the Centre (CGST) and the state (SGST, or UTGST in union territories). On 18%, that means 9% CGST + 9% SGST. On a sale to another state, the full 18% is charged as IGST. The total tax is the same either way.
GST rate changes from September 2025
The GST Council's rate rationalisation, effective 22 September 2025, moved most goods and services to two main slabs of 5% and 18%, with a special 40% rate for luxury and sin goods. Many daily-use items moved down from 12% to 5%, and many from 28% to 18%. Always check the current rate for your HSN or SAC code on the CBIC website.
Next step: make the invoice
Once you know the tax, create a proper GST bill with the free GST invoice generator. It works out CGST, SGST or IGST automatically from the states you pick, and writes the amount in words.
Frequently asked questions
What are the GST rates in India now?
Since 22 September 2025 the main GST slabs are 5% and 18%, with 40% for luxury and sin goods. Some items are exempt (0%), and special rates such as 0.25% and 3% (gold) still apply. The old 12% and 28% slabs now apply only to a small number of items.
How do I remove GST from an inclusive price?
Divide the inclusive price by (1 + GST rate ÷ 100). For ₹1,180 with 18% GST: 1,180 ÷ 1.18 = ₹1,000 net price, and GST is ₹180.
When do I charge CGST + SGST and when IGST?
If the seller and the place of supply are in the same state, charge CGST and SGST, each at half the rate. If they are in different states, charge IGST at the full rate.
Who must register for GST?
Businesses with turnover above ₹40 lakh for goods (₹20 lakh in some states) or ₹20 lakh for services (₹10 lakh in special category states) must register. Interstate sellers of goods and most e-commerce sellers must register regardless of turnover.