GST liability doesn't necessarily arise the moment money changes hands, or the moment goods are delivered. The law has specific rules — called 'time of supply' — to pin down exactly when tax becomes payable on a transaction, and getting it wrong can mean interest and penalties even if the tax is eventually paid.

Why Time of Supply Matters

The time of supply determines the tax period in which a transaction must be reported in returns, and the due date by which tax must actually be paid. Since GST operates on a monthly/quarterly return cycle, correctly identifying which period a transaction belongs to is essential — reporting it in the wrong period can trigger interest liability even though the total tax paid over time is correct.

Time of Supply of Goods (Section 12)

For goods, the time of supply is generally the earlier of: the date of issue of invoice (or the last date by which the invoice should have been issued under Section 31), or the date of receipt of payment.

In practice, since GST on advance receipts for goods has been given relief for most taxpayers (other than those under the Composition Scheme) through a specific notification, the invoice date is what usually governs the time of supply of goods for regular taxpayers.

Time of Supply of Services (Section 13)

For services, the time of supply is the earlier of:

•      The date of issue of invoice, if the invoice is issued within the prescribed period (typically 30 days of supply, or 45 days for banks/NBFCs)

•      The date of provision of service, if the invoice is not issued within the prescribed period

•      The date of receipt of payment, if it is earlier than either of the above

Time of Supply under Reverse Charge

Where tax is payable under RCM, the time of supply for goods is the earliest of: the date of receipt of goods, the date of payment (as per books of account or bank statement, whichever is earlier), or 30 days from the date of issue of invoice by the supplier.

For services under RCM, it is the earliest of: the date of payment, or 60 days from the date of issue of invoice by the supplier. If none of these can be determined, the date of entry in the recipient's books of account is used as a fallback.

Time of Supply in Special Cases

•      Vouchers: if the supply against a voucher is identifiable at the time of issue, time of supply is the date of issue of the voucher; otherwise, it is the date of redemption

•      Where time of supply cannot be determined under any of the above rules: it is the date on which the periodical return is filed, or the date on which tax is actually paid, whichever is earlier

•      Continuous supply of goods/services: time of supply is generally linked to the successive statements of account or successive payments as agreed

Frequently Asked Questions

Q1. Why does the exact time of supply matter for a business?

A. It fixes the return period and due date in which the transaction must be reported and tax paid, directly affecting interest and late-fee exposure even if the tax amount itself is undisputed.

Q2. Is GST payable immediately on an advance received for goods?

A. For most regular taxpayers, GST on advances received for supply of goods is not required to be paid at the time of receipt of advance, due to a specific notified relief — tax becomes payable at the time of invoice instead. This relief does not extend to composition taxpayers.

Q3. Does time of supply differ for services compared to goods?

A. Yes — for services, the actual date of provision of service can independently trigger the time of supply if invoicing is delayed beyond the prescribed period, which is a distinct rule not mirrored for goods in the same way.

Q4. What if I receive an advance payment for a service?

A. Unlike goods, GST liability on advances for services can arise at the time of receipt of payment if that is earlier than the invoice date or date of provision of service, under the general Section 13 rule.

Q5. How is time of supply determined for continuous services like AMC contracts?

A. It generally follows the due date of payment as specified in the contract, or the date of actual payment/invoice issuance linked to each periodic milestone, as agreed between the parties.

Q6. What happens if none of the standard time-of-supply triggers apply?

A. As a residual rule, the time of supply is taken as the date on which the relevant periodical GST return is filed, or the date tax is actually paid, whichever is earlier.