There's a particular kind of silence that follows sending an invoice to a corporate client or a builder, and if your format is wrong, that silence ends with their accounts team bouncing it back. For an interior design studio in India, the invoice isn't just a payment request, it's a tax document, and the format is not a matter of taste. Get it right and money moves, get it wrong and your payment sits in a queue while someone emails you about a missing state code. So let me lay out the interior design invoice format for India properly, field by field, with the design-business specifics that generic GST guides never cover.
The two invoices every studio actually raises
First, a distinction most format guides skip. A design studio in India raises two commercially different kinds of invoice, and mixing them up causes half the confusion.
The fees invoice bills your design services: consultation, concept, design development, site supervision. Services take an SAC code (995443 is the one interior design studios commonly use, at 18% GST) and the line items are stages or deliverables.
The supply invoice bills goods you're providing: furniture, modular units, lighting, soft furnishings. Goods take HSN codes, each category with its own rate, a wooden wardrobe, a mattress and a chandelier don't necessarily carry the same GST rate, and the line items are physical items with quantities.
Many projects need both, sometimes on one invoice with properly separated lines, sometimes as separate invoices per your CA's advice on your contract structure. The point is that your format must handle mixed supplies cleanly, one lazy "interior work, lumpsum" line at a single rate is how studios end up explaining themselves during an assessment.
The format, field by field
Here's the complete field list for a compliant tax invoice, with the studio-specific notes:
| Field | The studio-specific detail |
|---|---|
| "Tax Invoice" heading | Not "Bill", not "Proforma", those are different documents |
| Invoice number | Sequential, unbroken series per financial year, like DSG/2026-27/041 |
| Invoice date | The date of issue, which drives GST return periods |
| Your name, address, GSTIN | Studio's registered details, exactly as on the GST portal |
| Client name, address, GSTIN | Their GSTIN is mandatory if they're registered, it's how they claim credit |
| Place of supply with state code | For work on a property, usually the property's state, this decides the tax split |
| Line items | Stage or item description, SAC for services, HSN for goods |
| Quantity and unit | For goods lines, matching your delivery records |
| Rate and taxable value | Per line, before tax |
| Tax columns | CGST + SGST for intra-state, IGST for inter-state, shown separately per line |
| Total in figures and words | Both, and they'd better match |
| Reverse charge declaration | Usually "No" for design work, but the field must appear |
| Bank details / payment link | Not legally required, commercially essential |
| Signature | Physical or digital, of the supplier or authorised person |
The place-of-supply line is the one that trips studios with out-of-state projects. Your studio is registered in Delhi, the client's company is in Gurugram, the flat being designed is in Noida, and the tax treatment follows rules about where the service relating to immovable property is delivered, not where the emails go. When the split is wrong, the client's input credit jams, and jammed credit means your payment jams with it.
Line items: where design invoices go wrong
Format compliance is half the game, the other half is line-item hygiene, and this is pure design-business craft. Your invoice lines should trace to documents the client has already seen and approved. The fees lines trace to the stages in your agreement. The goods lines trace to your FF&E schedule, same item codes, same descriptions, same quantities, so the client's accountant can match invoice to delivery without a phone call. If your project runs on a bill of quantities for civil and carpentry work, the execution invoice lines mirror the BOQ items and measured quantities.
This traceability has a commercial superpower: it kills invoice disputes before they start. A line that says "LR-SOF-01, 3-seater sofa as approved, qty 1" against a recorded portal approval is unarguable. A line that says "furniture supply, lumpsum" is an invitation to negotiate after the fact.
Timing matters too. Invoice at the milestones the client agreed to, advance, design sign-off, deliveries, execution stages, handover, and raise the final invoice only after the snag or punch list is formally closed, because a final invoice sent while snags are open is a final invoice the client feels justified sitting on. The full rhythm sits inside the complete interior project checklist if you want the end-to-end view.
Numbering, series and the quiet compliance traps
Three small things that become big things during scrutiny. Your invoice numbers must form a continuous series, no gaps, no duplicates, across the financial year, which is exactly what breaks when invoices are made in Word by whoever is free that day. Credit notes for any reductions need their own proper series and reasons, you can't just reissue a smaller invoice and delete the old one. And your invoice dates need to align with when you actually report them in returns, backdating to a closed period is a mess your CA should never have to untangle.
None of these traps exists in a system where invoices are generated, numbered and logged automatically. All of them exist in a folder of Excel and Word files.
From format to flow
Here's my honest position after watching studios wrestle with this: you shouldn't be assembling invoices at all. The information already exists, the approved quote, the FF&E schedule, the milestones, and the invoice should be a one-click transformation of it. That's how Designa treats billing: the approved quote becomes a compliant GST invoice with the right SAC and HSN treatment, the CGST/SGST-versus-IGST decision handled from your registration and place of supply, the number series maintained automatically, a Razorpay payment link attached so the client can pay by UPI tonight, and the whole thing synced to Tally or Zoho Books so your accountant works from live books instead of your exports.
And because the invoice is the last document in a chain, everything upstream feeds its quality, the presentation the client approved (I've written a mood board checklist for making that approval solid), the schedule the goods trace to, and the project timeline the milestones hang on. If you're evaluating systems to run that whole chain, my buyer's guide for studio software in India is the place to start.
Before you hit send on any invoice
- Heading says Tax Invoice, number continues the series with no gap
- Client GSTIN present if they're registered, verified against the GST portal
- Place of supply and state code match the property, not the email address
- Every fees line carries an SAC, every goods line carries its HSN and rate
- Goods lines match FF&E item codes and delivered quantities
- Tax split correct for intra-state versus inter-state
- Totals in figures and words agree
- Payment link or bank details present
- Final invoice only after the snag list is closed
Frequently asked questions
What is the correct invoice format for interior designers in India?
A GST tax invoice with sequential numbering, both parties' GSTINs, place of supply with state code, SAC codes for design services and HSN codes for supplied goods, per-line tax split, totals in figures and words, and a signature.
Which SAC code do interior designers use?
Most studios bill interior design and decoration services under SAC 995443 at 18% GST, while supplied goods carry their own HSN codes and rates on separate lines.
Can I combine design fees and furniture supply on one invoice?
Yes, if the lines are properly separated with SAC for services and HSN for goods, each at its correct rate. Many studios also raise separate invoices, follow your CA's advice for your contract structure.
When should the final invoice be raised?
After the snag list is formally closed and handover is done, a final invoice sent over open snags is the one clients sit on.
Format is the floor, flow is the game, and a studio whose invoices generate themselves from approved work gets paid faster with fewer conversations. See a quote turn into a compliant GST invoice with a payment link at demo.designa.work, and the founding offer, one flat price for the whole studio billed in rupees, is at go.designa.work.