Almost every GST correction we see on a client's books comes back to one decision: which heads the tax lands under. Get it wrong and the total is often still right, which is exactly why it survives until someone reconciles the returns.
The rule itself is short. If the supply is intra-state — place of supply in the same state as the supplier — the tax splits into CGST and SGST, half to the centre and half to the state. If it is inter-state, a single IGST charge applies at the combined rate, and the states settle it between themselves afterwards.
Take a ₹50,000 service billed at 18%. Gujarat to Gujarat, that is ₹4,500 CGST plus ₹4,500 SGST. Gujarat to Maharashtra, it is ₹9,000 IGST. Both come to ₹59,000 payable, and that identical total is the trap: nothing about the amount tells you the heads were wrong.
What decides it is place of supply, which is not always the buyer's billing address. For most goods it follows delivery. For services it commonly follows the recipient's registered location, with specific rules for immovable property, events, transport and a handful of other categories.
Key takeaways
- Place of supply — not your own location — decides whether tax splits or stays integrated.
- The total is identical either way, so a wrong split will not show up as a wrong amount.
- A buyer's billing address is not automatically the place of supply; for goods, delivery usually governs.
- Inter-state invoices must carry the place of supply as a stated field, not an inference.
- Getting the heads wrong distorts the return, not the invoice — which is why it is caught late.
Practical checklist
- Record the place of supply per line, not once per invoice.
- Verify the customer's GSTIN before you rely on their state code.
- Check your treatment for services with special place-of-supply rules.
- Reconcile a sample of inter-state invoices against your GSTR-1 heads.
What to do next week
If you are deciding the heads by hand on every invoice, this is worth automating — not because the arithmetic is hard, but because the failure is silent. Envocify, our own GST invoicing platform, reads the place of supply and picks the heads per line, so an intra-state and an inter-state sale cannot end up under the same treatment. You can see how the split works on the product, or talk to us if your book-keeping is mid-migration.
How we work with clients at TechTrio
Every engagement at TechTrio Automation starts with a short discovery phase: we map your current stack, traffic, conversion paths, and operational bottlenecks. From there we propose a phased roadmap — quick wins first (tracking, analytics hygiene, performance, or a focused automation), then deeper builds (product modules, integrations, or marketing systems). Our teams in Ahmedabad and Mehsana collaborate closely with stakeholders in India, the UK, USA, Canada, and the UAE, so documentation, handoffs, and support hours stay practical.
We bias toward maintainable defaults: typed frontends where it pays off, predictable hosting on Vercel or similar for marketing sites, Firebase or Postgres depending on data and compliance needs, and observability so you are never guessing whether a workflow ran. Security is not an afterthought — least-privilege access, secrets outside the repo, and reviews for anything that touches payments or personal data.
If you are evaluating an agency or studio partner, ask for references in your industry, a clear definition of done, and a plan for what happens after launch. We publish these articles because we want founders and operators to make better decisions — whether or not you ever hire us. When you are ready for a deeper conversation, book a short session from our site and we will help you prioritise what to build, automate, or measure next.
Published by TechTrio Automation — web, mobile, SaaS, and AI automation from Gujarat, serving teams worldwide.
Related reading
- What a GST-compliant invoice must contain
- IRN and e-way bills, explained without the jargon
- How to choose GST invoicing software
Frequently asked questions
Is IGST charged at a higher rate than CGST plus SGST?
No. IGST is charged at the combined rate — 18% IGST is the same total as 9% CGST plus 9% SGST. The amount payable does not change; only the heads it is reported under do.
What decides intra-state versus inter-state?
The place of supply relative to the supplier's location. If both are in the same state, it is intra-state and the tax splits into CGST and SGST. If they differ, IGST applies.
Does the customer's billing address decide the place of supply?
Not always. For most goods, place of supply follows where the goods are delivered. For services it commonly follows the recipient's registered location, with separate rules for immovable property, events and transport.
