What a construction contractor’s tax invoice has to contain

Why the format is not up to you

The particulars a tax invoice must contain are prescribed under the CGST Rules. This is not formatting preference — an invoice missing a required particular is defective, and the practical consequence lands on the recipient, who may be denied input tax credit on it.

A client denied credit does not absorb the loss. They come back for a corrected invoice, and if the period has closed that correction is considerably more involved than issuing it correctly in the first place.

The particulars

Broadly, a compliant tax invoice carries the following. The exact list is in the rules and is worth reading once rather than inferring from a template someone sent you.

• Supplier name, address and GSTIN.
• A consecutive serial number, unique within the financial year, from a series that does not restart or skip.
• Date of issue.
• Recipient name, address and GSTIN where registered; for unregistered recipients above the prescribed value, name, address and state.
• Place of supply with the state name — and for works contract this is the location of the immovable property, not the office of either party.
• HSN or SAC code for the supply, at the digit depth applicable to your turnover.
• Description of the service, and for a works contract this means the work certified, not a bare reference to a bill number.
• Taxable value, after any discount given on the invoice itself.
• Rate and amount of tax, split into CGST and SGST, or IGST, according to the place of supply.
• Whether tax is payable on reverse charge.
• Signature or digital signature of the supplier or an authorised person.

Place of supply is the one that goes wrong

For services directly in relation to immovable property — which construction work is — the place of supply is where the property is located. Not where your office is, not where the client is registered.

This determines whether the transaction is intra-state, attracting CGST and SGST, or inter-state, attracting IGST. A contractor registered in Tamil Nadu building in Karnataka for a Tamil Nadu client is making an inter-state supply, and charging CGST and SGST on it is wrong in a way that is painful to correct — the tax has been paid to the wrong government, and the client cannot claim the credit.

The same applies in reverse, and the error is easy to make because the client relationship feels local.

RA bills and the time of supply

Works contracts are paid against running account bills, and the GST liability arises on the value certified in each, rather than on the contract as a whole.

When exactly that liability arises is governed by the time of supply rules, and the trigger is not simply the date typed on the bill — the date of issue, the prescribed period for issue, and the date of receipt of payment all interact. For a continuous supply of services, the contract’s own payment milestones feed into it.

This is worth settling with your CA at the start of a contract rather than at the first return, because the pattern repeats across every bill on that contract.

What this guide deliberately does not tell you

No rates. Works contract rates vary by project type — affordable housing, other residential, government work, commercial — and the concessional rates carry conditions on things like carpet area and the proportion of commercial space. There are also restrictions on input tax credit for certain categories of construction, which change the economics entirely.

No thresholds. Registration limits, the value above which an unregistered recipient’s details must be recorded, HSN digit requirements and e-invoicing applicability are all turnover-dependent and have been revised repeatedly.

Both change, and a wrong figure here would be acted on. The structure above is stable; the numbers are not. Get the rate applicable to your specific contract, and your e-invoicing position, confirmed by your CA before the first invoice goes out.

Practical invoicing discipline

Three habits prevent most of the avoidable problems.

• One unbroken serial series per financial year. Gaps and restarts invite questions at reconciliation, and cancelled numbers should be recorded as cancelled rather than reused.
• The site, named on the invoice. Beyond being the basis of the place of supply, it is what lets both sides tie the invoice to a project a year later.
• The certification reference on the invoice — which RA bill, which certified value. An invoice that cannot be traced to a certification is the one that gets held at the client’s accounts desk.