What must be included on an architect's invoice in India?

A GST-registered architect's tax invoice should include the prescribed invoice particulars, including invoice number and date, supplier details and GSTIN, recipient details where required, a description of service, the applicable SAC code, taxable value, tax details, and place of supply where required. Confirm the current rules for your supply with a GST professional.

When should an architect invoice their client in India?

Architects should invoice at each COA stage milestone — when the deliverable for that stage is completed and accepted by the client. Do not accumulate invoices or wait until project end. Invoice at appointment (retainer), after each design stage approval, on tender issue, and at construction milestones.

Finance · GST Compliance

How to Invoice Clients as an Architect in India (2026)

Q: How is the final architect invoice calculated when project costs change?

At project completion, the professional fee is regularised against the actual certified cost of completed works. If actual cost exceeded the estimate, the architect raises a supplementary invoice. If costs came in lower, the architect issues a credit note. This close-out regularisation is documented and agreed with the client.

By ArchiEase Updated April 2026 6 min read

Architects commonly raise invoices at agreed COA stage milestones rather than waiting until project completion. A GST tax invoice needs the prescribed particulars, including the applicable SAC code and tax treatment. Tie invoice timing and payment terms to the signed appointment; do not treat a generic schedule as a substitute for it.

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]"
Applicable SAC Code: use the code matching the service supplied (for example 998321, 998322, or 998323)
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.

What is the SAC code for architecture services in India?

There is no one SAC for all architecture services. CBIC lists 998321 for architectural advisory services, 998322 for residential building projects, 998323 for non-residential building projects, 998325 for urban planning, and 998328 for landscape architectural services. Select the code that matches the service supplied.

How is the close-out regularisation invoice calculated?

At project completion, the professional fee is recalculated against the actual certified cost of works. If actual cost exceeded the estimate, the architect raises a supplementary invoice for the additional fee plus documentation charges and GST. If costs came in lower, a credit note is issued. Always document this in writing with the client.