Q.A dealer purchases goods for Rs 6,000 (excluding GST) and pays GST at 18% (9% CGST + 9% SGST) on the purchase. He sells the goods for Rs 7,500 (excluding GST) within the same state, charging GST at the same rate. Find the net CGST and net SGST payable by him.

Compute input and output CGST/SGST separately, since their credits cannot mix, then take each difference.

Input CGST = 6,000 × 9/100 = Rs 540; input SGST = 6,000 × 9/100 = Rs 540 (equal, since both use the same 9% rate on the same purchase value).

Output CGST = 7,500 × 9/100 = Rs 675; output SGST = 7,500 × 9/100 = Rs 675.

Net CGST payable = 675 − 540 = Rs 135. Net SGST payable = 675 − 540 = Rs 135 (necessarily equal to net CGST payable here, since CGST and SGST always move together at equal rates on equal values). …

Alternative — value-added shortcut directly: value added = Rs 1,500; net CGST payable = 1,500 × 9% = Rs 135; net SGST payable = 1,500 × 9% = Rs 135 — reaches the s …

A serious, GST-specific error is trying to set off an excess of input CGST credit against an SGST liability (or vice versa) — CGST and SGST credits are tracked and set off completely separately (§3's note). In this example the two happen to …