You closed a lovely 12-lakh living room and bedroom project. The client is happy. Now you have to raise the invoice, and suddenly you are staring at a blank template wondering what an HSN code is, whether you charge CGST or IGST, and whether your GST number even needs to be on there. Sound familiar?
Most studio owners I talk to are brilliant at design and terrified of the invoice. That fear is expensive. A sloppy invoice means your client's accountant sends it back, your payment gets stuck for two weeks, and your input tax credit claim gets questioned. Let me walk you through exactly what a GST-compliant invoice for design work needs, in plain language, so you can raise one without calling your CA every single time.
First, do you even need to charge GST?
Quick reality check before we go further. If your studio's annual turnover is above ₹20 lakh (₹10 lakh in a few special-category states), you must register for GST and charge it. Below that, registration is optional but honestly most serious studios cross that line fast once you count design fees plus the furniture and material you supply.
If you are registered, every invoice you raise for taxable design work has to follow the tax invoice format under the CGST rules. There is no "small studio" exemption on the format. The rules are the same for you and for a 50-person firm. I've written a fuller breakdown in GST for Interior Designers in India if you want the ground-up version, but here we're going straight to the invoice itself.
The SAC code for interior design work
This is the one that trips everyone up. You know HSN codes are for goods. Design is a service, so you use a SAC code, which stands for Services Accounting Code. Same idea, different name.
For interior design and decoration services, the SAC most studios use is 9954 at the broad level, with the more specific code being 995443 for interior decoration and design services. Architectural services sit under 9983, with 998321 covering architectural advisory and design.
Here's the practical bit. If you only supply the design consultancy, you use the service SAC and charge 18% GST. But the moment you start supplying furniture, modular units, or finishes as part of the deal, those goods carry their own HSN codes and often their own GST rates. A wooden wardrobe, a sofa, tiles, lighting, all have separate HSN codes. This mixed nature is why interior invoices get complicated, and why you cannot just slap one rate on the whole thing and hope.
Two ways studios handle this:
- Split the invoice line by line. Design fee on the SAC 995443 line at 18%. Each supplied item on its own HSN line at its own rate. This is the cleanest and most defensible.
- Composite or works-contract treatment. If you're doing a turnkey fit-out where design and execution are bundled into one price, it may qualify as a works contract, which is treated as a service. The GST treatment here genuinely depends on your contract structure, so this is the one place I'd tell you to confirm with your CA rather than guess.
Get the codes right and your client's accountant relaxes immediately. Get them wrong and every line becomes a query.
CGST + SGST, or IGST? The one rule that decides it
This is simpler than people think, and it hinges entirely on one thing: where the supply happens versus where you're registered.
If your studio is registered in Karnataka and your client is also in Karnataka, it's an intra-state supply. You split the 18% into 9% CGST + 9% SGST. Two lines, adding up to 18%.
If your studio is in Karnataka and the client's project is in, say, Maharashtra, it's an inter-state supply. Now you charge 18% IGST as a single line. No CGST, no SGST.
The total tax the client pays is 18% either way. The split only changes who in the government gets it. But you must get the split right, because a wrong split messes up both your GST return and your client's input tax credit.
The trap for interior designers is figuring out where the supply actually happens, because your office, your client's billing address, and the actual site can all be in different states. For services tied to immovable property, like designing a specific home, the place of supply is usually the location of the property, not where the client's company is registered. That single detail can flip your whole invoice from CGST+SGST to IGST. I unpacked this properly in Place of Supply for Interior Design Services because it genuinely deserves its own read. Don't wing this part.
Every field your GST invoice must carry
Here's the checklist. Miss any of these and it's technically not a valid tax invoice, which means your client can't claim input credit on it and may bounce it back.
- The words "Tax Invoice" clearly at the top. Not "Bill", not "Estimate".
- A unique, sequential invoice number. It has to be a continuous series for the financial year, no gaps, no repeats. Something like DES/2026-27/0042.
- Date of issue.
- Your studio's name, address, and GSTIN.
- Client's name and address. If the client is GST-registered (a company, a builder), their GSTIN too. This is what lets them claim credit.
- Place of supply and the state name with its state code, especially for inter-state supplies.
- SAC code for each design service line, HSN for each goods line.
- Description of service or item, quantity, and rate.
- Taxable value for each line, then the tax split (CGST/SGST or IGST) with the rate and amount shown separately.
- Total invoice value in figures and in words.
- Whether tax is on reverse charge (usually "No" for design work, but the field must be there).
- Your signature or digital signature.
That's it. Not scary once it's laid out. But typing all of that manually into Word or Excel for every project, keeping the number series unbroken, and remembering the CGST/SGST switch is where mistakes creep in at 11pm before a payment deadline.
Stop building invoices from scratch
Here's my honest take after watching too many studios lose days to this. The invoice is the least creative thing you do all month, and it's the thing most likely to delay your money. It should be automatic.
That's exactly why we built invoicing into Designa the way we did. You spec the project room by room, the client approves the mood boards and quote online, and when it's time to bill, that approved quote becomes a GST invoice in a couple of clicks. The SAC and HSN codes carry through. The CGST/SGST-versus-IGST decision is handled based on your registration state and the place of supply, so you're not doing mental math on every bill. The invoice number series stays continuous automatically, which matters more than people realise when a return gets scrutinised. I walked through that flow in How to Turn a Quote Into a GST Invoice in Minutes.
And because getting the invoice out is only half the job, we made collection part of the same step. You send the GST invoice with a Razorpay payment link attached, the client pays by UPI or card from their phone, and the payment reconciles against the invoice. No more "please share your account details" over WhatsApp three times. That whole loop is covered in How to Send GST Invoices and Collect Payment via Razorpay.
Then, so your CA doesn't chase you at month-end, everything syncs across to your books. If your accountant lives in Tally, your invoices flow there without re-entry, which I detailed in How to Sync Your Studio Invoices With Tally. Zoho Books too. Raise it once, and it's in the right place everywhere.
The bottom line
A GST-compliant invoice for design work isn't complicated once you know the three things that matter: use the right SAC code (995443 for interior design) plus proper HSN codes for anything you supply, get the CGST+SGST-versus-IGST call right based on place of supply, and include every mandatory field so your client can actually claim credit. Do that and you get paid faster with zero back-and-forth.
But you shouldn't be doing it by hand every time. Your studio's price is one flat ₹2,299 + GST a year for the whole team, up to 10 members, with unlimited free client logins, done-for-you onboarding and data migration, and a 7-day money-back guarantee. Poke around a real studio setup at demo.designa.work, and when you're ready to raise clean, compliant invoices without the month-end panic, grab the founding offer at go.designa.work. Your future self, staring at a blank invoice at 11pm, will thank you.