Why Half the GST on a Local Bill Goes to the State and Half to the Centre
Work out CGST, SGST and IGST on any bill, find the price paid after a discount, calculate GST when a shopkeeper makes a profit or loss, and reverse the working to find a list price, cost price or GST rate from the tax paid.
How is GST worked out on a bill?
Look at any shop bill and you will see a line for tax. Goods and Services Tax (GST) is added to the price of most goods and services at a fixed percentage called the GST rate. The shopkeeper collects it from the buyer and passes it on to the government.
The basic rule is simple:
This part covers how GST is split, and how to handle discounts, profit and loss, and reverse problems.
The basic rule is simple:
This part covers how GST is split, and how to handle discounts, profit and loss, and reverse problems.
How do you calculate CGST, SGST and IGST for sales within a state and between states?
For a sale within one state, GST is split equally into CGST for the Centre and SGST for the State; for a sale from one state to another, the whole GST is charged as IGST.
- Intra-state sale —
- Inter-state sale —
Worked example — within a state. An article costs ₹2400 and the GST rate is .
Worked example — between states. The same article sent from one state to another:
An everyday example. A bill from a shop in Pune for a mixer bought in Pune shows CGST and SGST at each, while an online order shipped from another state shows IGST at .
The substance. The buyer pays exactly the same total either way; only the division of the tax between governments changes.
- Intra-state sale —
- Inter-state sale —
Worked example — within a state. An article costs ₹2400 and the GST rate is .
Worked example — between states. The same article sent from one state to another:
An everyday example. A bill from a shop in Pune for a mixer bought in Pune shows CGST and SGST at each, while an online order shipped from another state shows IGST at .
The substance. The buyer pays exactly the same total either way; only the division of the tax between governments changes.
How do you find the total price paid when a discount is given on the list price?
Subtract the discount from the list price first to get the selling price, then charge GST on that selling price.
Steps:
- Discount
- Taxable value list price discount
- GST on the taxable value, then add
Worked example. A jacket has a list price of ₹5000. The shop gives discount and charges GST at . The sale is within the state.
An everyday example. During a festive season sale, the price tag shows the list price, but the bill charges GST only on the reduced price.
The misconception. Charging GST on the list price is wrong. It would give , which is ₹60 too much.
Steps:
- Discount
- Taxable value list price discount
- GST on the taxable value, then add
Worked example. A jacket has a list price of ₹5000. The shop gives discount and charges GST at . The sale is within the state.
An everyday example. During a festive season sale, the price tag shows the list price, but the bill charges GST only on the reduced price.
The misconception. Charging GST on the list price is wrong. It would give , which is ₹60 too much.
How do you find the taxable value and GST when a shopkeeper makes a profit or a loss?
Find the selling price from the cost price and the profit or loss percentage first; that selling price is the taxable value on which GST is charged.
Worked example — profit. A shopkeeper buys a washing machine for ₹8000, excluding tax, and sells it at a profit of . GST is .
Worked example — loss. A trader buys an old stock of shoes for ₹6000 and sells at a loss of . GST is .
An everyday example. An electronics dealer in Chennai marks up a television, and the GST on the customer's bill is worked out on the dealer's selling price, not on what the dealer paid.
The substance. Profit is calculated before GST is added; the tax is collected for the government and is not part of the shopkeeper's profit.
Worked example — profit. A shopkeeper buys a washing machine for ₹8000, excluding tax, and sells it at a profit of . GST is .
Worked example — loss. A trader buys an old stock of shoes for ₹6000 and sells at a loss of . GST is .
An everyday example. An electronics dealer in Chennai marks up a television, and the GST on the customer's bill is worked out on the dealer's selling price, not on what the dealer paid.
The substance. Profit is calculated before GST is added; the tax is collected for the government and is not part of the shopkeeper's profit.
How do you find the list price, cost price or GST rate when the tax paid is given?
Write the unknown as a letter, form an equation using the percentage rules, and solve; when the total includes GST, divide by the multiplier rather than subtracting a percentage of the total.
Worked example 1 — price from the total. A customer pays ₹1888 including GST. Find the price before tax.
Worked example 2 — rate from the tax. On an article priced at ₹1000, the CGST charged is ₹90. Find the GST rate.
Worked example 3 — list price with a discount. A customer pays ₹3186 for a bag after a discount, with GST. Find the list price .
An everyday example. Checking a restaurant bill that shows only the final total, you can find the food cost by dividing by the GST multiplier.
The misconception. **Subtracting of the total is wrong**: , not ₹1600, because the was calculated on the smaller amount.
Worked example 1 — price from the total. A customer pays ₹1888 including GST. Find the price before tax.
Worked example 2 — rate from the tax. On an article priced at ₹1000, the CGST charged is ₹90. Find the GST rate.
Worked example 3 — list price with a discount. A customer pays ₹3186 for a bag after a discount, with GST. Find the list price .
An everyday example. Checking a restaurant bill that shows only the final total, you can find the food cost by dividing by the GST multiplier.
The misconception. **Subtracting of the total is wrong**: , not ₹1600, because the was calculated on the smaller amount.
Exam tip
What earns full marks on GST calculations?
Show each step on its own line — discount, taxable value, GST, split, total — and state whether the sale is intra-state or inter-state.
- Always find the taxable value first, after any discount
- Split GST equally into CGST and SGST for sales within a state
- Use IGST for sales between states
- Write units as ₹ on every amount
- For reverse problems, set up an equation with a letter for the unknown
- Check your answer by working forward again
The trap. Adding CGST and SGST as if each were the full rate. **At GST, CGST and SGST are each**, not each.
- Always find the taxable value first, after any discount
- Split GST equally into CGST and SGST for sales within a state
- Use IGST for sales between states
- Write units as ₹ on every amount
- For reverse problems, set up an equation with a letter for the unknown
- Check your answer by working forward again
The trap. Adding CGST and SGST as if each were the full rate. **At GST, CGST and SGST are each**, not each.
Did you know
Why is GST called a destination-based tax?
Suppose a phone is made in one state and sold to a customer in another. Which state gets the tax?
Under GST, the tax goes to the state where the goods are finally consumed, not the state where they were made. That is why GST is called a destination-based tax.
IGST makes this possible. The Centre collects IGST on inter-state sales and passes the state's share on to the consuming state.
Under GST, the tax goes to the state where the goods are finally consumed, not the state where they were made. That is why GST is called a destination-based tax.
IGST makes this possible. The Centre collects IGST on inter-state sales and passes the state's share on to the consuming state.
Exam relevance
Is GST tested in JEE Main, or only in the ICSE board exam?
GST itself is not part of the JEE Main syllabus; it is a Class 10 ICSE board-exam topic, where it usually appears as a multi-step word problem.
What carries forward. The habit of turning a percentage change into a multiplier, such as for adding or for a discount, is exactly the idea behind the common ratio of a geometric progression in Class 11 Sequences and Series, a JEE Main chapter. Repeated percentage changes multiply, just like terms of a GP.
Board versus competitive emphasis. The board paper rewards clear working and correct splitting of tax; competitive exams reward fast, accurate use of multipliers.
The trap that costs marks. Taking a percentage of the final total when reversing a calculation — always divide by the multiplier instead.
What carries forward. The habit of turning a percentage change into a multiplier, such as for adding or for a discount, is exactly the idea behind the common ratio of a geometric progression in Class 11 Sequences and Series, a JEE Main chapter. Repeated percentage changes multiply, just like terms of a GP.
Board versus competitive emphasis. The board paper rewards clear working and correct splitting of tax; competitive exams reward fast, accurate use of multipliers.
The trap that costs marks. Taking a percentage of the final total when reversing a calculation — always divide by the multiplier instead.
Key takeaways
What must you be able to do from this part?
- GST taxable value
- Intra-state: CGST SGST half the GST; inter-state: IGST full GST
- **₹2400 at : GST ₹432, CGST and SGST ₹216 each, total ₹2832
- Discount first**: ₹5000 less is ₹4500; GST at is ₹540
- Profit or loss: selling price is the taxable value; ₹8000 at profit gives ₹10000 and GST ₹1800
- Reverse problems: divide by the multiplier; ₹1888 including GST means ₹1600 before tax
Take the last shop bill at home, cover the tax lines, and see if you can work them out from the prices and rates.
- Intra-state: CGST SGST half the GST; inter-state: IGST full GST
- **₹2400 at : GST ₹432, CGST and SGST ₹216 each, total ₹2832
- Discount first**: ₹5000 less is ₹4500; GST at is ₹540
- Profit or loss: selling price is the taxable value; ₹8000 at profit gives ₹10000 and GST ₹1800
- Reverse problems: divide by the multiplier; ₹1888 including GST means ₹1600 before tax
Take the last shop bill at home, cover the tax lines, and see if you can work them out from the prices and rates.