CGST Act · Chapter IV
Time and Value of Supply
s. 12Time of supply of goods
Section 12 fixes when the liability to pay tax on goods arises, and so in which return period the tax is due. For a supplier it is the earlier of invoicing and payment; for a recipient paying on reverse charge, the earliest of receipt, payment and thirty days after the supplier's invoice.
- Under section 12(2) of the CGST Act, 2017 the time of supply of goods is the earlier of the date of the invoice (or the last date by which it should have been issued under section 31) and the date the supplier receives payment.
- Advances for goods do not, in practice, attract tax at receipt: Notification 66/2017-Central Tax applies the invoice date alone to suppliers of goods other than composition taxpayers.
- For goods on reverse charge, the time of supply is the earliest of receipt of goods, payment, or the day after thirty days from the supplier's invoice (section 12(3)).
- The rule for vouchers in section 12(4) was omitted from 01.10.2025 by the Finance Act, 2025.
s. 13Time of supply of services
Section 13 does for services what section 12 does for goods. The difference that matters most is that advances for services are taxed when received, and that, for reverse charge, the supplier's invoice starts a sixty-day clock — or, where the recipient must itself raise the invoice, the recipient's invoice fixes the date.
- Under section 13(2) of the CGST Act, 2017 the time of supply of services is the earlier of the invoice date and the payment date if the invoice is issued within the time under section 31; otherwise the earlier of the date of provision of service and payment.
- Advances received for services are taxable on receipt.
- For services on reverse charge, the time of supply is the earlier of payment and the day after sixty days from the supplier's invoice; from 01.11.2024, where the recipient must issue the invoice (purchases from unregistered suppliers), it is the date of the recipient's invoice.
- For services from an associated enterprise abroad, the time of supply is the earlier of the entry in the recipient's books and payment.
s. 14Change in rate of tax
When a rate changes — as it did across most goods on 22.09.2025 — section 14 decides whether a transaction straddling the change bears the old or the new rate. It overrides sections 12 and 13 and works on three events: the supply, the invoice and the payment.
- Section 14 of the CGST Act, 2017 overrides sections 12 and 13 to fix the time of supply where the rate changes.
- Where any two of the three events — supply, invoice and payment — fall after the change, the new rate applies; where two fall before, the old rate applies.
- For this purpose, a payment credited to the bank more than four working days after the change is taken at the date of the bank credit.
s. 15Value of taxable supply
Section 15 decides the amount on which tax is charged. The starting point is the transaction value — the price actually paid or payable — where the parties are not related and price is the sole consideration. Additions, permitted discounts and the valuation rules for everything else follow.
- Under section 15(1) of the CGST Act, 2017 the value of a supply is the transaction value — the price actually paid or payable — where supplier and recipient are not related and the price is the sole consideration.
- The value includes other taxes and levies (but not GST and compensation cess), the supplier's liabilities paid by the recipient, incidental expenses, interest or late fee for delayed payment, and price-linked subsidies other than government subsidies (section 15(2)).
- A discount after supply is excluded from value only if it was agreed at or before the supply, is linked to the invoices, and the recipient reverses the related credit (section 15(3)(b) as in force); the Finance Act, 2026 relaxes this, but that amendment has not yet been brought into force.
- Where transaction value cannot be used — related persons, non-monetary consideration and others — the value is determined under Rules 27 to 35 of the CGST Rules.