Interstate projects sound glamorous till the first invoice. You landed a farmhouse in Alibaug while your studio is registered in Bengaluru. Or a Gurugram client wants their Goa villa done. Suddenly your accountant is asking questions you didn't think about when you signed the deal, and someone on WhatsApp is telling you "no GST on out-of-state work" which is completely wrong.
Let me clear this up the way I wish someone had cleared it up for me. This is the plain-English version of IGST, place of supply, and how to bill when your studio and your project sit in different states.
First, what actually changes when you cross a state line
GST has two flavours depending on whether a supply is inside your state or across states.
- Same state as your registration: you charge CGST + SGST (split half-half).
- Different state: you charge IGST (one single rate, same total).
The total tax the client pays is identical. On an 18% job, whether it's CGST 9% + SGST 9% or IGST 18%, the client still pays 18. IGST isn't an extra tax. It's just the correct label when the supply crosses a border. So the person telling you interstate work is tax-free, or that it's somehow "extra taxed", both wrong.
The real question is never "do I charge GST." You always do (once you're registered). The real question is: which label, and based on what? That's decided by "place of supply."
Place of supply is the whole game
Place of supply is the state the government treats as the destination of your service. Get it right and IGST-vs-CGST/SGST sorts itself out automatically. Get it wrong and you've either short-charged, over-charged, or filed under the wrong head, and fixing that later is a headache with your CA.
For interior design work there's a fork in the road, and it trips up nearly everyone.
Design and consultancy vs work "in relation to immovable property"
Pure design, drawings, 3D visualisation, consultancy, the default place of supply is the location of your registered client (their GSTIN state). So a Mumbai studio doing concept drawings for a Delhi-registered company: place of supply is Delhi, you charge IGST.
But the moment your service is tied to a specific property, site execution, turnkey fit-out, supervision of the actual space, GST law leans toward the location of the immovable property as the place of supply. That villa in Goa? The property sits in Goa, so place of supply can be Goa regardless of where the client's office is registered.
This is exactly why so many studios get confused. The same client, the same project, can pull two different answers depending on whether you're billing "design fees" or "execution/site work." I broke this fork down properly in Place of Supply for Interior Design Services, Explained, if you do a lot of out-of-state work, read that one slowly. It's the single most misfiled thing in our industry.
The practical takeaway: decide place of supply per invoice line, based on what that line actually is. Don't slap one tax head across a mixed invoice out of laziness.
A real example, in rupees
Say you're a Pune-registered studio. Client is a company registered in Hyderabad. Project is their Hyderabad apartment. Contract splits into design fees and execution supervision.
Design fees of ₹4,00,000: this is consultancy, place of supply follows the client, Hyderabad. Interstate from Pune. So IGST 18% = ₹72,000. Invoice total ₹4,72,000.
Execution supervision of ₹2,00,000 tied to the physical Hyderabad flat: place of supply is where the property sits, also Hyderabad. Still interstate from your Pune registration. IGST 18% = ₹36,000.
Now flip it. Same Pune studio, but the client is registered in Pune too, and the flat is in Pune. Everything is intra-state. Same ₹6,00,000 of fees, but now it's CGST 9% + SGST 9%. Client pays the same total. Only the labels changed.
See the pattern? Compare your registration state against the place of supply. Same = CGST+SGST. Different = IGST. That's the entire decision.
If the maths of building these lines, HSN/SAC codes, and tax splits feels fiddly, that's normal, I walked through a clean, compliant invoice structure in How to Raise a GST-Compliant Invoice for Design Work. Interstate just swaps the tax head; the rest of the invoice discipline is the same.
The mistakes I see again and again
Charging CGST+SGST on an interstate supply. Feels safe because it's what you always do locally. But it's wrong, and your client's accounts team will bounce it because they can't claim input credit cleanly against the wrong head. You'll be reissuing invoices.
Assuming the client's billing address decides everything. For property-linked execution, it doesn't. The property location can override. A Delhi client doesn't make a Goa site into a Delhi supply.
*Ignoring where the client is registered vs where the person lives.* Place of supply for services to a registered business follows their GSTIN state, not the individual's home. For an unregistered individual client, different rules apply, usually their address on record. Know which bucket your client is in before you cut the invoice.
Forgetting advances. Interstate advances get taxed at the time you receive them, under IGST, at the point the place of supply is interstate, not later when you invoice the milestone. If you take a mobilisation advance for a Goa villa, the tax clock starts on receipt. I unpacked this properly in How to Handle Client Advances and GST the Right Way, because advances are where interstate studios quietly build up compliance debt.
Thinking you need a GST registration in the other state. For most design studios providing services across states, you do NOT need a separate registration in every state you work in. You bill IGST from your home registration. (A physical fixed place of business or a warehouse in another state is a different story, talk to your CA if you're setting up shop there.) But for the typical "we're in one state, project's in another" case: one registration, IGST invoices. Don't let anyone scare you into pointless multi-state registrations.
Do this before you sign the interstate deal
A little discipline up front saves you from month-end firefighting:
- Get the client's GSTIN and registered state in writing at onboarding. Not the WhatsApp number's area code, the actual GSTIN.
- Note the property's state separately. For split scopes, you'll need both.
- Decide, per scope line, whether it's design/consultancy (follows client) or execution/property-linked (follows property).
- Confirm your quote already shows the right tax head so there's no awkward "actually it's IGST" conversation after approval.
That last one matters more than it sounds. When your quote, your client's approval, and your final invoice all carry the same tax treatment, nobody argues at payment time. That's the whole reason I built the quote-to-invoice flow the way I did, the tax head you set at quote stage carries straight through to the GST invoice, so an interstate project doesn't quietly turn into an intra-state invoice by accident.
Where a proper system earns its keep
Here's the honest bit. None of this is hard once. It's hard at scale, across a dozen live projects in five states, when three are advances, two are property-linked execution, and you're doing it in a spreadsheet at 11pm before filing.
That's exactly the mess Designa is built to take off your plate. Your client sits in one place, your project in another, the platform holds the client's GSTIN and state, the project's location, and lets you bill the right tax head per line without you re-deriving place-of-supply logic every single time. Quotes become GST invoices with the tax treatment intact. Razorpay collects. And when your CA wants it all in Tally, it syncs, I covered that pipeline in How to Sync Your Studio Invoices With Tally so your interstate invoices land in your books with the correct heads, no re-keying.
If GST itself still feels shaky, thresholds, when you must register, RCM, all of it, start with GST for Interior Designers in India: A Plain-English Guide and build up from there. Interstate is just one layer on top of a solid GST foundation.
The short version
Interstate work is not scary and not tax-free. You charge the same total GST, you just label it IGST instead of CGST+SGST when your registration state and the place of supply differ. Decide place of supply per scope: design follows the client's state, property-linked execution follows the property's state. Capture GSTIN and property location at onboarding. Don't over-register. And don't let a spreadsheet decide your tax head at midnight.
Working across state lines is a sign your studio is growing. Let the billing keep up cleanly.
See how interstate quotes, IGST invoices, Razorpay collection and Tally sync fit into one connected workspace, try it live at demo.designa.work or grab the founding offer for your whole studio at go.designa.work.