Hello, and welcome to today's mathematics lesson. We are going to explore an essential topic that affects every purchase you make — Goods and Services Tax, commonly known as GST. By the end of this lesson, you will understand what GST is, how it replaced older tax systems, the different types of GST, and how to calculate it in various business transactions.
Let us begin.
Every government needs money to function — for roads, schools, hospitals, salaries, and public services. This money comes from taxes. In India, we have two broad categories of taxes. First, direct taxes, which are levied directly on your income — like income tax and corporate tax. Second, indirect taxes, which you pay when you buy goods or services. Before July 2017, India had many indirect taxes — VAT, excise duty, service tax, and several others. This created complexity, confusion, and sometimes double taxation.
On the first of July, 2017, the government introduced GST to simplify this entire system.
Let us understand the basic definitions. Goods mean any movable property — anything you can physically move from one place to another. This does not include money or securities like shares, stocks, bonds, or debentures. Services mean anything other than goods, money, and securities. Banking, insurance, transportation, and consulting are all examples of services.
GST is a consumption-based tax — you pay it when you buy or use goods and services. It is levied at every point of sale, and it applies throughout the country. Most importantly, GST eliminated the old problem of tax on tax, called the cascading effect. Now, tax is applied only on the value added at each stage.
Only registered businesses can charge and collect GST. They must display their GST registration number on every bill. This brings transparency and accountability to the system.
GST is also a destination-based tax. This means the tax goes to the government where the goods or services are finally consumed, not where they are produced.
Now, let us examine the four components of GST.
First, CGST, or Central GST, collected by the central government on transactions within the same state — what we call intra-state supply. Second, SGST, or State GST, collected by the state government on these same intra-state transactions. Third, UGST, or Union Territory GST, which applies in union territories instead of SGST. And fourth, IGST, or Integrated GST, collected by the central government on transactions between different states — called inter-state supply, including imports.
Here is the crucial rule: for intra-state transactions, the GST rate is split equally between CGST and SGST. For inter-state transactions, the entire tax is IGST. If a problem does not specify whether a sale is intra-state or inter-state, you should assume it is intra-state.
Let me illustrate with an example. Imagine a dealer in Bhopal, Madhya Pradesh, supplies goods worth eight thousand rupees to someone in Indore, also in Madhya Pradesh. The GST rate is twenty-eight percent. Since both cities are in the same state, this is intra-state. The twenty-eight percent splits into fourteen percent CGST and fourteen percent SGST. So CGST equals fourteen percent of eight thousand, which is one thousand one hundred twenty rupees. SGST is also one thousand one hundred twenty rupees. IGST is zero.
Now, if the same dealer in Bhopal supplies goods worth eight thousand rupees to someone in Agra, Uttar Pradesh, this becomes inter-state. Here, CGST and SGST are both zero. IGST equals twenty-eight percent of eight thousand, which is two thousand two hundred forty rupees.
When calculating GST, always remember: discounts are deducted first. GST applies to the selling price after discount, never to the marked price directly. Also, never apply discount to a price that already includes GST.
Unless a problem states otherwise, assume cost price and selling price exclude GST.
Let us work through a complete intra-state example. A dealer buys goods worth six thousand rupees from the same city. The GST rate is eighteen percent. Since this is intra-state, we split eighteen percent into nine percent CGST and nine percent SGST. CGST equals nine percent of six thousand, which is five hundred forty rupees. SGST is also five hundred forty rupees. IGST is zero. The total amount paid equals six thousand plus five hundred forty plus five hundred forty, which is seven thousand eighty rupees.
Now consider an inter-state service example. M K Traders in Delhi provides services costing five hundred, three hundred, four hundred, and six hundred rupees to Rakesh in Agra. The total service value is one thousand eight hundred rupees, and GST is twelve percent. Since Delhi to Agra is inter-state, Rakesh pays IGST of twelve percent of one thousand eight hundred, which is two hundred sixteen rupees. CGST and SGST are both zero. The total amount Rakesh pays is one thousand eight hundred plus two hundred sixteen, equaling two thousand sixteen rupees.
If the same services were provided to Raj in Delhi, this would be intra-state. Raj would pay six percent CGST and six percent SGST on one thousand eight hundred, which is one hundred eight rupees each. The total remains two thousand sixteen rupees, but the tax distribution differs.
Here is a more complex intra-state example with multiple items and discounts. Consider four items with marked prices of two hundred fifty, two hundred, one hundred fifty, and three hundred rupees. The discounts are thirty percent, forty percent, thirty-two percent, and twenty percent respectively. The GST rate is twelve percent. First, calculate the discounted selling price for each. For the first item, seventy percent of two hundred fifty equals one hundred seventy-five rupees. For the second, sixty percent of two hundred equals one hundred twenty rupees. For the third, sixty-eight percent of one hundred fifty equals one hundred two rupees. For the fourth, eighty percent of three hundred equals two hundred forty rupees. The total selling price is six hundred thirty-seven rupees. CGST equals six percent of six hundred thirty-seven, which is thirty-eight rupees and twenty-two paise. SGST is identical. The final bill amount is six hundred thirty-seven plus thirty-eight point two two plus thirty-eight point two two, totaling seven hundred thirteen rupees and forty-four paise.
Now let us turn to a fundamental concept: GST on value addition.
This is the heart of the GST system. Every business pays GST on its purchases and collects GST on its sales. The business only deposits the difference to the government. This ensures tax is paid only on the value added at each stage.
Consider a trader who buys an item for five thousand rupees with twelve percent GST. The GST paid on purchase is six hundred rupees — this is called input tax. The trader sells it to a consumer at a profit of one thousand rupees, so the selling price is six thousand rupees. The GST collected on sale is twelve percent of six thousand, which is seven hundred twenty rupees — this is output tax. The trader deposits seven hundred twenty minus six hundred, which is one hundred twenty rupees to the government.
Notice this equals twelve percent of the one thousand rupee profit — the value addition. This is why GST is called a tax on value addition.
Let us apply this to a multi-state chain. Trader A in one state sells goods to Trader B for five hundred rupees. Trader B sells to Trader C for seven hundred rupees, making a two hundred rupee profit. The GST rate is twelve percent. For Trader A, this is inter-state, so IGST equals twelve percent of five hundred, which is sixty rupees. This becomes Trader B's input tax. Trader B's sale is also inter-state, so output tax equals twelve percent of seven hundred, which is eighty-four rupees. Trader B's tax liability is eighty-four minus sixty, equaling twenty-four rupees. Again, this equals twelve percent of the two hundred rupee value addition.
Here is another practical scenario. A product moves from Kanpur to Varanasi within Uttar Pradesh, then from Varanasi to Ranchi in Jharkhand. The first sale is for twelve thousand rupees with eighteen percent GST. Since this is intra-state, CGST and SGST are each nine percent of twelve thousand, which is one thousand eighty rupees. The Varanasi dealer's total input tax is two thousand one hundred sixty rupees. The second sale is inter-state with a four thousand rupee profit, so selling price is sixteen thousand rupees. Output tax is eighteen percent of sixteen thousand, which is two thousand eight hundred eighty rupees. Net GST payable at Varanasi is two thousand eight hundred eighty minus two thousand one hundred sixty, which equals seven hundred twenty rupees. This matches eighteen percent of the four thousand rupee profit.
Sometimes you need to work backwards from the total invoice value. Suppose a toy car's total invoice is two hundred eighty-one rupees and sixty paise, with twenty-eight percent GST. Let the taxable value be x. Then x plus twenty-eight percent of x equals two hundred eighty-one point six. This means one point two eight x equals two hundred eighty-one point six. Solving, x equals two hundred twenty rupees. CGST and SGST are each fourteen percent of two hundred twenty, which is thirty rupees and eighty paise.
Let us recap the essential points you must remember.
First, GST replaced multiple indirect taxes from July 2017, creating a unified national system. Second, intra-state transactions split GST equally into CGST and SGST, while inter-state transactions use IGST exclusively. Third, always calculate GST on the selling price after discount, never on the marked price. Fourth, GST is fundamentally a tax on value addition — businesses deposit only the difference between output tax and input tax. Fifth, cost price and selling price are assumed exclusive of GST unless stated otherwise. Sixth, current GST rates in India are zero, five, twelve, eighteen, and twenty-eight percent, with essential goods taxed lower and luxury goods higher.
That brings us to the end of our lesson on Goods and Services Tax. You now understand how this modern tax system works, why it was introduced, and how to perform calculations involving different types of transactions. These skills will serve you not just in examinations, but in understanding the real world of business and commerce around you.
Keep practicing with different scenarios, pay attention to whether transactions are intra-state or inter-state, and always verify your calculations. Thank you for your attention, and I look forward to our next mathematics lesson.