Sales returns, billing mistakes and after-sale discounts all end the same way: you charged more GST than was finally due. The law gives you one instrument to correct it, the credit note under Section 34 of the CGST Act. Issue it in the right format and on time, and your liability drops in the next return. Issue it wrongly or late, and the excess tax stays paid.
When a credit note is the right document
- Goods returned: the buyer sends back part or all of a supply.
- Deficient goods or services: quality disputes settled with a price reduction.
- Overbilling: wrong rate, wrong quantity, or tax charged higher than applicable.
- Post-sale discount: where the discount was agreed before or at the time of supply.
The reverse case, where you undercharged, calls for a debit note (a supplementary invoice), not a credit note.
Credit note vs debit note under GST
Both are issued by the supplier and both adjust an already-issued tax invoice, but they move the liability in opposite directions.
| Point | Credit note | Debit note |
|---|---|---|
| Who issues it and why | The supplier, when the invoice value or tax was too high (returns, deficiency, overbilling, agreed discount) | The supplier, when it was too low (under-charged rate or quantity, upward price revision) |
| Effect on GST liability | Reduces the supplier's output tax | Increases it |
| Effect on the buyer | The buyer must reverse excess input tax credit | The buyer can claim additional credit |
| Where it appears | Declared in GSTR-1 (and flows into GSTR-3B); bound by the Section 34(2) 30 November deadline | Declared in GSTR-1 (and flows into GSTR-3B); no such time limit for reporting |
Mandatory fields in a GST credit note
- Supplier's name, address and GSTIN
- A unique serial number (its own series, not the invoice series) and the date of issue
- Recipient's name, address and GSTIN (or delivery address for unregistered buyers)
- Reference to the original tax invoice, with its number and date
- The taxable value credited, and the rate and amount of CGST + SGST or IGST reversed
- Signature or digital signature of the supplier or authorised signatory
The deadline most businesses miss
Section 34(2) sets a hard clock: the credit note must be declared in a return no later than 30 November following the end of the financial year of the original supply (or the annual return date, if earlier). A March 2026 invoice, for instance, can be credited with GST effect only until 30 November 2026. After that, a credit note can still settle accounts commercially, but it cannot reduce your GST liability. Apna Invoice tracks this window per invoice and warns you before it closes.
How the tax reversal works
The credit note reverses tax at the same rate and in the same heads as the original invoice (CGST + SGST for a same-state supply, IGST for inter-state), in proportion to the amount credited. It reduces your outward liability in GSTR-1 and GSTR-3B for the period you declare it, and the buyer (if registered) must reverse the matching input tax credit. To sanity-check any split, use the free GST calculator.
Issue compliant credit notes, free
In Apna Invoice, a credit note is two clicks from the invoice it corrects: pick a reason, enter the amount (full or partial), and the CGST/SGST/IGST reversal, serial numbering, invoice reference and Section 34 deadline check are handled for you. The buyer gets a PDF and the reversal flows into your GSTR-1. Create a free account, or start from the GST invoice format guide if you're setting up your billing from scratch.
Frequently asked questions
When should I issue a credit note under GST?
Under Section 34 of the CGST Act, a supplier issues a credit note when the taxable value or tax charged on an invoice exceeds what was actually due: goods returned by the buyer, goods found deficient, a post-sale discount agreed in advance, or an invoicing error that overcharged the customer.
What must a GST credit note contain?
The supplier's name, address and GSTIN; a unique serial number and date; the recipient's details (GSTIN if registered); the number and date of the original tax invoice; the taxable value being credited with the rate and amount of CGST/SGST or IGST reversed; and the signature of the supplier or authorised person.
What is the deadline for issuing a GST credit note?
A credit note must be declared in a GST return no later than 30 November following the end of the financial year in which the original supply was made (or the date of the annual return, if earlier). After that window closes, a credit note cannot reduce your GST liability; only a commercial adjustment outside GST is possible.
Does a credit note reduce my GST liability?
Yes, that is its purpose. The tax reversed on the credit note reduces your outward liability in GSTR-1/GSTR-3B for the period, provided it is declared within the Section 34(2) window and the buyer reverses any input tax credit they claimed.
Can I issue a partial credit note?
Yes. A credit note can cover part of an invoice, for example one returned item out of five, or a percentage discount. The tax reversal is calculated proportionately on the credited amount at the same rate as the original supply.
What is the difference between a credit note and a debit note?
A credit note reduces the value or tax of an original invoice: you charged too much, so your GST liability goes down. A debit note does the opposite: you charged too little (higher rate, extra quantity, price revised up), so it raises the value and increases liability. The supplier issues both. A credit note lowers what the buyer owes and requires them to reverse any excess input tax credit; a debit note increases what the buyer owes and lets them claim additional credit. Both are reported in GSTR-1.