Worked Example — Indian Commerce and Logistics

The invoice that crossed a state line

Sameer had been at the D2C textile brand in Surat for five weeks when the finance team rejected his invoicing module. The company sold fabrics directly to small retailers and designers across India — mostly through its own website and, increasingly, through ONDC. Sameer had built the invoicing system. It calculated prices, applied taxes, generated PDF invoices, and emailed them to buyers. It worked perfectly for every order he had tested.

The finance team tested it with a real order. A retailer in Pune had ordered twelve thousand rupees of fabric from the Surat warehouse. The invoice showed CGST and SGST — Central GST and State GST — totalling eighteen percent. The finance controller circled the tax line in red and wrote two words: "Wrong tax."

The order was inter-state. Goods moving from Gujarat to Maharashtra are subject to IGST — Integrated GST — not CGST plus SGST. CGST and SGST apply when the seller and buyer are in the same state. IGST applies when they are in different states. The tax rate is the same eighteen percent, but the tax type is different, the tax code on the invoice is different, the input tax credit treatment is different, and the return filing is different. An invoice with the wrong tax type is not just a display error. It is a compliance failure that affects the buyer's ability to claim input tax credit and the seller's GST return.

Sameer had not known there were two different ways to apply the same tax rate. He had implemented GST as a single flat percentage because that was what the product spec said. The spec, written by an engineer, not by the finance team, had not distinguished between intra-state and inter-state transactions.