Finance · GST Compliance

How to Invoice Clients as an Architect in India

By ArchiEase Updated April 2026 6 min read

Architects in India should raise invoices at each COA stage milestone — not at the end of the project. Every GST-registered architect's tax invoice must include their GSTIN, the SAC code (998311), the taxable value, and CGST/SGST. Invoice on the day of the milestone, state payment terms clearly, and never advance to the next stage if the previous invoice is unpaid.

When to Invoice

Invoice at every COA stage milestone — the moment you deliver what you promised for that stage and the client accepts it. Do not accumulate invoices. Every week of delay is a week of cash flow you give away for free.

Typical invoice triggers:

Retainer: Before any work starts — on signing the appointment letter
Stage 1: When concept design is presented and accepted by client
Stage 2: When preliminary design is accepted
Stage 3A: On submission to statutory authorities
Stage 3B: On receipt of statutory approval
Stage 4: When working drawings and tender set are issued
Stage 5: On contractor appointment
Stage 6: On construction drawings release, then at 20/40/60/80% progress and virtual completion
Stage 7: On completion and as-built delivery

What Every Tax Invoice Must Include

For GST-registered architects, a tax invoice must contain:

Invoice number (sequential, unique)
Invoice date
Architect/firm name and address
GSTIN of the architect
Client name, address, and GSTIN (if registered)
Description of service — e.g. "Architectural Design Services — Stage 2: Preliminary Design, Project: [Name]"
SAC Code: 998311
Taxable value
CGST (9%) and SGST (9%), or IGST (18%) for inter-state
Total amount payable
Place of supply
Payment due date
Bank account details for payment

How to Calculate the Invoice Amount

Each invoice covers the incremental amount due at that milestone. For a project with a ₹10,00,000 professional fee (before documentation charges and GST):

Stage	Cumulative %	Cumulative Fee	Less Previously Billed	This Invoice
Retainer	5%	₹50,000	—	₹50,000
Stage 1	10%	₹1,00,000	₹50,000	₹50,000
Stage 2	20%	₹2,00,000	₹1,00,000	₹1,00,000
Stage 3A	30%	₹3,00,000	₹2,00,000	₹1,00,000

Documentation charges (10% of professional fee) are either spread across invoices or billed as a separate line item at each stage. GST at 18% is applied to the total of professional fee + documentation charges.

Payment Terms

State the payment due date on every invoice. Standard practice is 15 or 30 days from the invoice date. Your appointment letter should also include a late payment interest clause — typically 1–2% per month on overdue amounts.

When the Client Disputes an Invoice

Do not proceed to the next stage while an invoice is under dispute. Document all communication in writing (email is sufficient). If the dispute is about the amount, refer to the appointment letter and COA payment schedule. If it is about quality of deliverables, get specific written feedback and address it formally. Verbal disputes become expensive — always put resolution in writing.

Close-Out Regularisation Invoice

At project completion, the professional fee must be regularised against the actual cost of works. If actual cost exceeded the estimate, you raise a supplementary invoice. If it came in lower, you issue a credit note or apply the surplus against the final invoice. Document this clearly — it is often a point of dispute.

Frequently Asked Questions

Can an architect charge interest on overdue invoices in India?

Yes, if the appointment letter includes a late payment interest clause. The agreed rate (typically 1–2% per month) applies to the overdue amount from the due date. Without this clause in the contract, interest is harder to enforce.

Do documentation charges need to appear as a separate line on the invoice?

It is better practice to show documentation charges as a separate line item (10% of professional fee), so the client can see exactly what they are paying for and the invoice clearly matches the appointment letter.

What if the client does not have a GSTIN?

If the client is an individual without a GSTIN (common for residential projects), you can issue the tax invoice without a client GSTIN. The invoice is still valid. The place of supply is typically the location of the property.