GST Invoice for Interior Designers in India: The Complete 2026 Guide
If you bill an interior project in India and your turnover crosses ₹20 lakh (₹10 lakh in special category states), GST compliance is not optional. This is the complete 2026 guide to issuing GST-compliant invoices for interior design, modular work, and turnkey contracts.
Bookmark it. The rules and rates change every couple of years; this page reflects the current 2026 state.
When you must register for GST
- Turnover above ₹20 lakh (services) in most states.
- ₹10 lakh in special category states (NE states, J&K, etc.).
- Any inter-state taxable supply (even ₹1 to another state).
- E-commerce sellers — from day one.
If you only design (no supply of goods) and stay below the threshold, registration is optional. The moment you start invoicing materials or supply-and-fix, you should register.
What rate applies to interior work?
Most interior design and contracting attracts 18% GST, with two main buckets:
- Pure design services (SAC 998391 / 998391x): 18%.
- Works contract / supply and fix: 18% (composite supply rule).
- Modular furniture (HSN 9403): 18%.
Smaller items can attract 12% or 28% — for the full breakdown, see our GST rates for interior work guide.
Mandatory fields on a tax invoice
A GST tax invoice must contain:
- Your business name, address, and GSTIN.
- Invoice number — unique, sequential, max 16 characters, alphanumeric.
- Invoice date.
- Recipient's name, address, GSTIN (if registered).
- Place of supply — state name and code.
- HSN/SAC code per row.
- Description of goods/services.
- Quantity, unit, rate, taxable value.
- CGST + SGST (intra-state) or IGST (inter-state) per row and as totals.
- Total invoice value in figures and words.
- Reverse charge applicability (yes/no).
- Signature (digital or physical) of authorised signatory.
Miss any of these and your client cannot claim input tax credit. They will not pay until you reissue.
Intra-state vs inter-state
- Place of supply = your state: charge CGST 9% + SGST 9% (total 18%).
- Place of supply ≠ your state: charge IGST 18%.
For interior projects, place of supply is usually the site address — not the client's billing address. A Mumbai studio doing a Pune project charges Maharashtra CGST+SGST. A Mumbai studio doing a Bengaluru project charges IGST.
Tax invoice vs proforma vs bill of supply
- Tax invoice — registered supplier, taxable supply. Goes into GSTR-1.
- Proforma — pre-invoice draft for advance collection. Does not go into returns.
- Bill of supply — composition dealers and exempt supplies. No tax shown.
Do not mix these up. We covered the full distinction in quotation vs estimate vs invoice.
E-invoicing thresholds
As of 2026, e-invoicing is mandatory for businesses with aggregate turnover above ₹5 crore. Below that, regular tax invoices apply. Most interior studios stay below this threshold; modular brands and large contractors should check.
Timing — when to issue
- Services: within 30 days of supply.
- Goods: at the time of dispatch.
- Continuous supply: as per contract milestones.
For turnkey interior projects with milestones, issue an invoice at each milestone trigger, not at the end.
Common GST mistakes interior studios make
- No HSN/SAC per row. Required for invoices over ₹5 crore turnover; best practice for all.
- CGST+SGST instead of IGST on out-of-state projects. Client cannot claim ITC.
- Place of supply = billing address. Should be site address for installation work.
- Skipping advance proforma. Then issuing tax invoice for the full amount at end — client loses early ITC.
- Editing invoice numbers. They must be sequential and unique per financial year.
- No digital signature on PDF invoices. Some clients (especially large corporates) reject them.
A sample compliant GST invoice (interior turnkey)
TAX INVOICE
[Studio Name] GSTIN: 27AAACI1234A1Z5
[Address, City, State - PIN] PAN: AAACI1234A
Phone: +91 9XXXXXXXXX
Invoice No: INT/2026-27/0042 Date: 12 Apr 2026
Place of Supply: Maharashtra (27) Reverse Charge: No
Bill To:
[Client Name] GSTIN: 27ABCDE5678F1Z2
[Client Billing Address]
Ship To: [Site Address]
Sl Description SAC/HSN Qty Unit Rate Taxable CGST 9% SGST 9% Total
1 Master Bedroom wardrobe 9403 56 sqft 1450 81,200 7,308 7,308 95,816
2 Living room TV unit 9403 14 rft 2200 30,800 2,772 2,772 36,344
...
Subtotal: 8,50,000
Discount (3%): 25,500
Taxable value: 8,24,500
CGST @9%: 74,205
SGST @9%: 74,205
Grand Total: 9,72,910
Amount in words: Nine Lakh Seventy-Two Thousand Nine Hundred Ten Only.
Bank Details: [Account, IFSC] Authorised Signatory
How software helps
Manual GST is brittle. Software that knows interior workflows:
- Auto-applies CGST+SGST or IGST based on state codes.
- Maintains sequential invoice numbers per financial year.
- Stores HSN/SAC by item.
- Exports GSTR-1 ready data for your accountant.
Intorza handles all of this and converts approved quotations into compliant tax invoices in one click.
What to do next
If your last 3 invoices are missing HSN/SAC or place of supply, reissue them this week. The cost of a compliance notice dwarfs the cost of a clean invoicing tool.
Frequently asked questions
Do I charge GST on the design fee separately?
Yes. Design fee is a service (SAC 998391), 18%. Show it as a separate row.
What if my client refuses to share GSTIN?
Issue the invoice as B2C — no ITC for them, but you remain compliant.
Is reverse charge applicable?
Generally no, for design and works contracts to private clients. Specific scenarios (services from unregistered suppliers, certain notified services) attract RCM.
Can I issue a single invoice for the whole project at the end?
Possible, but it hurts your cash flow and your client's ITC schedule. Milestone-wise invoicing is standard.