How GST Is Calculated in India (With Simple Examples)

Ordered biryani — menu ₹200, bill ₹236. Friend says "that's 18% GST." Another says "9+9." Who's right? Both, kind of. Let me explain GST the way I wish someone explained to me when I started freelancing.

What is GST?

Goods and Services Tax — one indirect tax replacing many older taxes (for most goods/services). Registered businesses charge it, file returns, claim input credit (if eligible). You as consumer see it on bills.

Common rates in India

5%, 12%, 18%, 28% — plus some items at 0% or exempt. Restaurant services often 5% (no ITC) or 18% depending on setup — check the bill.

Add GST to a base price (exclusive)

Service quote: ₹10,000 + GST at 18%.

GST = 10,000 × 18% = ₹1,800

Total = ₹11,800

For intra-state sale, split: CGST 9% + SGST 9% = 18%

Remove GST from MRP (inclusive)

Tag says ₹1,180 inclusive of 18% GST.

Base = 1,180 ÷ 1.18 = ₹1,000

GST portion = ₹180

Use our GST calculator — pick add or remove mode.

IGST vs CGST/SGST

Same state: CGST + SGST (half each).

Different state: IGST (full rate in one line).

Buying laptop online from another state? You'll often see IGST on invoice.

Quick shopping example

Shoes MRP ₹2,950 inclusive at 18%:

Base ≈ ₹2,500, GST ≈ ₹450

During sale "flat 30% off" — discount usually on pre-GST or post-GST depending on store policy; check final payable.

Freelancer tip

If you're GST registered and charge clients, your invoice shows taxable value + GST. If not registered, you don't charge GST — but you still pay GST when you buy things.

Mistakes to avoid

• Adding 18% on already inclusive price (double tax feel)
• Forgetting GST on reverse calculation when comparing quotes
• Mixing up 5% and 18% services on same bill without reading breakup

GST isn't evil — it's just maths on the bill. Once you know add vs remove, you're faster than the calculator app you deleted last year.

GST on restaurant bills — why two rates confuse people

Restaurants without ITC claim often charge 5% GST. Others charge 18%. Your ₹500 meal might show different tax than your friend's identical-looking café — check the bill breakup, not assumptions.

Invoice fields you should read

Look for GSTIN of seller, taxable value, CGST/SGST or IGST lines, and total. For B2B, wrong GSTIN means ITC headache — fix before paying.

Small business owner basics

Below threshold? You might not need registration — but you can't charge GST either. Above threshold, registration is mandatory. This article won't replace a CA; it helps you understand bills and quotes.

Worked example: freelancer invoice

You quote ₹25,000 + 18% GST for a Delhi client (same state). Taxable ₹25,000, GST ₹4,500, total ₹29,500. CGST ₹2,250 + SGST ₹2,250. Client pays ₹29,500; you remit GST to government per filing rules.

Reverse calculation for shopping

Flipkart shows "inclusive of taxes" — to know pre-tax margin, divide by (1 + rate/100). Sellers think in base; buyers see MRP. Both sides benefit from the same maths.