How do I calculate GST in ICSE Class 10 Maths for intra-state and inter-state sales?

Question

ICSE Class 10 GST chapter: I get confused between CGST, SGST and IGST, and how to find input tax credit and the tax payable by each dealer in a chain.

GradeHunt_Team · Answer

Intra-state sale (seller and buyer in the same state):
GST is split equally into CGST and SGST.
Example: goods worth Rs 10,000 at 18% GST. CGST = 9% = Rs 900, SGST = 9% = Rs 900, total GST = Rs 1,800.

Inter-state sale (different states):
Only IGST is charged, at the full rate.
Example: goods worth Rs 10,000 at 18%. IGST = Rs 1,800.

Input tax credit (ITC):
A dealer who pays GST on purchases can set it off against GST collected on sales.
GST payable by a dealer = Output GST (on sales) - Input GST (on purchases).

Chain example (all in one state, 18% GST):
A sells to B for Rs 5,000. B sells to C, the consumer, for Rs 6,000.
- A (first in the chain, so no input tax): output GST = 18% of 5,000 = Rs 900, paid as CGST Rs 450 + SGST Rs 450.
- B: output GST = 18% of 6,000 = Rs 1,080; input = Rs 900; payable = Rs 180 (CGST Rs 90 + SGST Rs 90).
- C pays Rs 6,000 + Rs 1,080 = Rs 7,080 in total.
Total tax reaching the government = 900 + 180 = Rs 1,080, which equals the GST on the final sale value.

Questions give the rate to use. Some still use 12% or 28%, which applied to many goods before the GST rate changes of 22 September 2025. Use the rate given; the method stays the same.

Common mistakes:
1. Charging CGST and SGST on an inter-state sale.
2. Adding the GST to the next dealer's cost price. The price at which B buys for GST purposes is Rs 5,000, not Rs 5,900.

Exam tip: make a small table for each dealer (sale price, output GST, input GST, GST payable). It keeps each dealer's figures separate and makes your working easy to follow.

How do I calculate GST in ICSE Class 10 Maths for intra-state and inter-state sales?

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