Time of Supply under GST: Determining the Exact Date of Tax Liability

In the Goods and Services Tax (GST) system, "Time" is as important as "Tax Rate." You may have sold a product in March, but if the law determines that the Time of Supply fell in February, you are already late.

The Time of Supply is the precise moment when the tax becomes "due" to the government. This date determines which month's GSTR-1 and GSTR-3B return you must include the transaction in. If you report it even one month late, the system will automatically levy 18% interest compounded daily.

The rules for Goods and Services differ significantly, especially regarding advance payments. This guide explains the Time of Supply rules under Sections 12 and 13 for the 2026 Assessment Year.

Why Time of Supply Matters

The GST portal's data analytics engine cross-references your E-invoice date against your filing date.

• If an invoice is dated February 28, but filed in the March GSTR-1, the system flags it.
• If an advance was received for a service in January, but the GST was only paid in February upon invoicing, the interest starts ticking from January.

Time of Supply for Goods (Section 12)

For the supply of goods, the Time of Supply is the Earliest of the following:

1. Date of Issue of Invoice (or the last date on which the invoice was required to be issued).
2. Date of Provision of Goods (when the goods are made available to the buyer).

The Advance Payment Rule for Goods

Since 2017, the government has provided a major relief for goods: GST is NOT payable on advances received for goods.

If a customer pays you a ₹1 Lakh advance for a machine in January, but you ship the machine and issue the invoice in February, the Time of Supply is in February. You do not pay tax in January.

Time of Supply for Services (Section 13)

Services follow a stricter rule compared to goods. For services, the Time of Supply is the Earliest of:

1. Date of Issue of Invoice (if the invoice is issued within the 30-day statutory limit).
2. Date of Receipt of Payment (including advances).
3. Date of Provision of Service (if the invoice is NOT issued within 30 days).

The Advance Payment Trap for Services

Unlike goods, GST MUST be paid on advances received for services.

If you are a consultant and a client pays you ₹50,000 as a retainer in March, but you only finish the work and invoice them in April, the Time of Supply is March. You must pay the GST in your March GSTR-3B.

Time of Supply for Reverse Charge (RCM)

When you are the buyer paying tax under the Reverse Charge Mechanism (RCM), the rules shift to focus on the date of payment and the invoice age.

The Time of Supply for RCM is the Earliest of:

1. Date of Payment (recorded in your books of account).
2. 61st Day from the date of issue of invoice by the supplier.

Example: If a lawyer issues an invoice to your company on February 1, but you haven't paid them by April 3, the 61st day (April 2) becomes the Time of Supply. You must pay the GST in April even if the lawyer remains unpaid.

Continuous Supply of Services

For long-term contracts (like 2-year construction projects or annual AMC services), where payments are made periodically:

• The Time of Supply is the date when the milestone/payment becomes due as per the contract.
• If the due date is not mentioned, it is the date when you receive the payment or issue the invoice.

Legal Reference

Relevant Law: Section 12 (Goods) and Section 13 (Services) of the CGST Act, 2017. Notification No. 66/2017 - Central Tax provides the exemption for advances on goods.

Common Mistakes with Time of Supply

1. Forgetting GST on Service Advances: Accountants often wait for the final invoice to calculate GST. For services, this leads to massive interest demands if an advance was received months earlier.
2. Issuing Invoices Late: Under Section 31, you must issue an invoice within 30 days of completing a service. If you issue it on the 45th day, the government considers the "Date of Provision of Service" as the Time of Supply, making your tax payment retroactively late.
3. Inter-company Charges: In mergers or branch transfers, companies often book "management fees" at the end of the year. If the service was provided throughout the year, the "Time of Supply" could be interpreted as the date of provision, leading to massive interest on the delayed year-end entries.

Conclusion

Time of Supply is the foundation of tax discipline. While the exemption on advances for goods provides significant cash-flow relief, businesses in the service sector must maintain a "Receipts Register" that is reconciled weekly to ensure that every advance received is correctly taxed in the same month. To further protect against interest penalties, always ensure your Tax Invoices are issued immediately upon the completion of service or delivery of goods.