A post-sale discount does not automatically reduce GST merely because the supplier issues a credit note. The tax question is narrower: does the discount satisfy the conditions that let it come out of the value of supply? If it does, the supplier can examine a tax adjustment under the CGST Act. If it does not, the parties may still agree a commercial reduction in price, but the original GST value does not fall merely because an accounting credit note was raised.
The starting point is Section 15 of the CGST Act on value of taxable supply. As of 14 September 2026, CBIC's Tax Information Portal shows a Finance Act, 2026 substitution for Section 15(3)(b), but expressly marks that substitution as yet to be notified. That means businesses should not read the enacted future wording as though it were already the operative rule.
What the current Section 15(3)(b) test requires
For a discount given after supply, the presently operative Section 15(3)(b) framework requires two things before the discount can be excluded from taxable value: the discount must have been established in terms of an agreement entered into at or before the time of supply and be specifically linked to relevant invoices; and the recipient must reverse the input tax credit attributable to that discount on the basis of the supplier's document.
This is why a year-end volume rebate can qualify even though its exact amount is known only later. The commercial scheme can be fixed in advance—for example, an additional 2% rebate if annual purchases cross an agreed quantity—and the final rebate can then be calculated after the period closes. CBIC's Circular No. 92/11/2019-GST specifically discusses periodic or year-end volume discounts of this kind and says they can be excluded from value when the Section 15(3) conditions are satisfied, including the recipient's attributable ITC reversal.
Example: an agreed annual volume rebate
Assume a distributor agreement signed before supplies begin says the dealer will receive an additional 2% rebate if annual purchases exceed an agreed volume. During the year, invoices are raised at normal prices. At year-end the threshold is crossed and the supplier calculates the rebate invoice by invoice. Because the discount mechanism existed before or at the time of supply, the invoices can be specifically identified, and the recipient reverses the ITC attributable to the discount, the arrangement can be tested under Section 15(3)(b) for exclusion from taxable value.
The evidence matters as much as the label. A vague statement such as “discount may be given at management discretion” is not the same as a pre-existing discount arrangement whose basis can be demonstrated. Keep the agreement, scheme circular, dealer communication, calculation sheet, invoice mapping and evidence of recipient-side ITC reversal together.
A commercial credit note can exist without a GST reduction
Now take a different case. A supplier sells goods at an agreed price and, months later, decides to grant an extra price concession that was not part of any agreement or discount scheme when the supplies were made. The supplier can still issue a financial or commercial credit note as a matter between the contracting parties. But under the current Section 15(3)(b) rule, that later discretionary concession does not satisfy the pre-agreement condition needed to reduce taxable value.
Circular 92 makes this distinction explicit for secondary discounts: a commercial credit note may be issued even when Section 15(3)(b) is not satisfied, but such a discount is not excluded from the value of supply merely because that note exists. In practical terms, the books may show a lower receivable or revenue amount while the GST originally charged remains unaffected.
This is the point at which many reconciliations go wrong. Accounting teams sometimes treat every credit note as a “GST credit note”. Instead, the file should first answer why the consideration changed and whether the statutory value conditions are met. Only then should the tax treatment be decided.
Do not rely on Circular 105/24/2019-GST
Search results and old compliance notes may still surface CBIC Circular No. 105/24/2019-GST on secondary or post-sales discounts. It should not be treated as operative guidance. CBIC's Circular No. 112/31/2019-GST, dated 3 October 2019, withdrew Circular 105 ab initio. For the discount principles discussed here, Circular 92 remains the relevant CBIC clarification to read with the Act.
Where Section 34 fits into the analysis
Section 15 answers whether the discount can reduce the taxable value. Section 34 of the CGST Act deals with credit and debit notes and the corresponding tax adjustment mechanics. These provisions should be read together rather than using Section 34 as a substitute for the valuation test.
The current Section 34 text requires a credit note to be declared no later than 30 November following the end of the financial year in which the supply was made, or the date of furnishing the relevant annual return, whichever is earlier, for the statutory tax adjustment. It also contains recipient-side protection for reduction of the supplier's output tax liability. A commercial note issued outside the statutory tax-adjustment route can still have accounting effect, but it should not be assumed to reopen GST liability automatically.
For a broader explanation of when credit notes and debit notes are used, see CA Samaaj's GST credit note vs debit note guide. The narrower issue here is whether a discount qualifies to reduce the value on which GST was computed.
The Finance Act, 2026 change is enacted but not yet operative
There is an important transition point to monitor. The official Section 15 page displays a Finance Act, 2026 substitution that would replace the present pre-agreement and invoice-linkage formulation in Section 15(3)(b) with a credit-note and recipient-ITC-reversal based formulation. However, the same official page states that the substitution is yet to be notified. The official Section 34 page similarly marks the related Finance Act, 2026 insertion concerning discounts as yet to be notified.
Accordingly, a business dealing with a post-sale discount on 14 September 2026 should apply the law that is actually in force, not the future text merely because Parliament has enacted it. Once the commencement notification is issued, the analysis will need to be refreshed for supplies and credit notes falling under the operative amended provisions.
A working-paper approach that keeps the tax position defensible
- Identify when the discount was agreed. Preserve the contract, scheme letter, email or policy showing whether the discount terms existed before or at the time of supply.
- Map the discount to supplies. Keep invoice-level or otherwise defensible workings showing which supplies generate the rebate and how the amount was computed.
- Separate tax notes from commercial notes. A financial concession can be valid commercially even where it does not qualify to reduce GST value.
- Verify recipient ITC reversal. Where tax value is being reduced under Section 15(3)(b), retain evidence supporting the recipient-side reversal attributable to the discount.
- Check Section 34 timing. Test the 30 November or earlier annual-return cut-off before assuming that output tax can be adjusted through the statutory credit-note mechanism.
- Check the law on the transaction date. Because the Finance Act, 2026 amendment has been enacted but not yet brought into force as of the verification date, confirm whether a commencement notification has appeared before processing later transactions.
A useful internal control is to add a “GST value reduction eligible?” field to the credit-note approval workflow. The approver should not answer it from the document name. The answer should come from the Section 15 conditions, the supporting agreement and invoice mapping, the recipient's ITC consequence and the Section 34 timing. That separates a genuine tax adjustment from a purely commercial price concession and makes the year-end GST reconciliation far easier to defend.
