In add mode, the amount you enter is the taxable value and GST is added on top. In remove mode, the amount already includes GST, so the base is back-calculated by dividing by (100 + rate) and multiplying by 100 — not by simply subtracting the rate, which is the most common error.

For supplies within the same state, GST is split equally into Central GST and State GST. For supplies across states, the entire amount is Integrated GST.

Add GST: Base ₹10,000 at 18% → GST = 10,000 × 0.18 = ₹1,800 → total = ₹11,800

Intra-state: CGST ₹900 + SGST ₹900  ·  Inter-state: IGST ₹1,800

Remove GST: Total ₹11,800 at 18% → base = 11,800 × 100/118 = ₹10,000 → GST = ₹1,800

Note that 11,800 − 18% = ₹9,676, which is wrong — the reverse calculation must use 100/(100+R).

• Standard GST slabs in India are 0%, 5%, 12%, 18% and 28%, with special rates of 0.25% and 3% for certain goods.
• Compensation cess applies to some items over and above GST and is not included here.
• Reverse charge, composition scheme and input tax credit are outside the scope of this calculator.
• Always verify the correct HSN/SAC code and its applicable rate before invoicing.

How do I remove GST from a price?
Divide by (100 + rate) and multiply by 100 — do not just subtract the percentage.

CGST + SGST or IGST?
CGST and SGST for supplies within a state; IGST for supplies between states.

Is GST charged on the discounted price?
Yes — GST applies to the taxable value after any discount shown on the invoice.