Credit Note vs Debit Note in GST: Rules, Format and Time Limit (2026)

A customer returns part of an order. Or you spot, after the invoice is already filed, that you under-billed a client by two units. Either way, the invoice is done — it's in your GSTR-1, your buyer may have already claimed input tax credit on it, and GST law does not let you go back and edit it.

What it lets you do instead is issue a second, linked document that corrects the first one without touching it: a credit note when the customer was charged too much, a debit note when they were charged too little. Both are defined in Section 34 of the CGST Act, 2017, and both have rules about what they must contain, how they're numbered, and — for one of the two — a deadline.

The short answer

	Credit Note	Debit Note
Issued when	Invoice value/tax was too high	Invoice value/tax was too low
Effect on your liability	Reduces what you owe	Increases what you owe
Typical triggers	Sales return, post-sale discount, deficiency in service, overcharge	Under-billing, freight/extra charges added later, price escalation
Also called	—	A supplementary invoice
Time limit to declare it	Yes — 30 Nov after the financial year (or annual return date)	No equivalent deadline
Reported in GSTR-1	Table 9B	Table 9B
Must reference the original invoice?	Yes, number and date	Yes, number and date

What is a credit note

A credit note is what you issue when the original invoice charged the customer more than what's actually owed. Under Section 34(1), that covers:

• Goods returned, wholly or partly
• Deficiency in services found after billing
• Post-sale discounts agreed after the invoice was raised
• Any case where the taxable value or tax charged exceeds what's actually payable — a pricing or quantity error found late, for instance

Issuing a credit note reduces your output tax liability for the period it's declared in. It doesn't touch the original invoice, which stays exactly as filed.

What is a debit note

A debit note — Section 34(3) also calls it a supplementary invoice — is the mirror case: the original invoice charged too little. Common triggers:

• Under-billing — a quantity or rate error that shortchanged you, not the customer
• Freight, packing or other charges identified after the invoice was raised
• Price escalation clauses that kick in later
• Any case where the taxable value or tax charged is less than what's actually payable

A debit note increases your output tax liability. Like a credit note, it references the original invoice rather than replacing it.

What a credit or debit note must contain

Rule 53(1A) of the CGST Rules doesn't prescribe a fixed template, but it does require every note to carry:

• The words "Credit Note" or "Debit Note", prominently
• Your name, address and GSTIN
• A consecutive serial number, unique for the financial year, of not more than 16 characters
• Date of issue
• Name, address and GSTIN of the recipient (or their address and state, if unregistered)
• The original invoice's number and date — this is the link the whole system depends on
• The taxable value, GST rate and tax amount of the goods or services being adjusted
• Signature or digital signature of the supplier or an authorised signatory

Give it its own number series

A credit note or debit note must not share a number series with your tax invoices. Keep three separate, unbroken series — for example INV-2026-27/001, CN-2026-27/001, DN-2026-27/001 — the same discipline Rule 46 asks for on invoices themselves. Mixing document types into one series is the easiest way to break the sequence GST expects.

The rate has to be the original invoice's rate — not today's

This is the detail that trips people up, and it's more relevant now than it used to be. A note adjusts an existing invoice, so it must carry that invoice's GST rate, not whatever rate applies today.

That stopped being a theoretical point on 22 September 2025, when GST 2.0 retired the 12% and 28% slabs. If you're crediting a return against an invoice raised before that date at 12% or 28%, the credit note still has to show 12% or 28% — re-rating it to the nearest surviving slab would produce a document that doesn't match the invoice it's correcting, and a GSTR-1 entry that reconciles with nothing.

Credit notes have a deadline. Debit notes don't.

Section 34(2) puts a hard limit on credit notes: you must declare one, in a return, by whichever is earlier of —

• 30 November following the end of the financial year the original supply was made in, or
• the date you file your annual return for that financial year

Miss it, and the credit note can still be issued for your own records, but it can no longer be used to reduce your GST liability. There's no equivalent limit on debit notes — Section 34(4) lets you declare one for the period it's actually issued in, whenever that is, since a debit note only ever increases what you owe.

Since 1 October 2025: your reduction depends on your buyer reversing their credit

A change under the Finance Act 2025 (Notification 16/2025-CT) added a real condition to Section 34(2): you can reduce your output tax liability via a credit note only if —

• for a registered recipient — they reverse the input tax credit attributable to that credit note, if they'd availed it, or
• for other cases — the incidence of tax hasn't been passed on to anyone else

In practice, this runs through the GST portal's Invoice Management System: your buyer has to accept the credit note and declare whether they're reversing the ITC. You can issue the note either way, but your liability only drops once that reversal is recorded on their side — worth flagging to a buyer rather than assuming it happens automatically.

From 1 April 2026: post-sale discounts got simpler

A further change via the Finance Act 2026 amended Section 15(3)(b): a post-sale discount can now be excluded from taxable value through a credit note without needing a pre-existing agreement tied to specific invoices, which the older rule required. Section 34(1) was updated to name post-sale discounts explicitly as valid grounds for a credit note. The condition above — the recipient reversing the attributable ITC — still applies. If you regularly issue volume or scheme discounts after the sale, this is worth a closer look with your CA, since it changes what documentation you need to keep.

How this shows up in your returns

A credit or debit note isn't folded into the original invoice's figures — it's reported as its own document, in Table 9B of GSTR-1, alongside the invoice number and date it references.

In GSTR-3B, Table 3.1(a) nets them against your invoices for the period: outward taxable supplies = invoices + debit notes − credit notes. In a month where returns outweigh sales, that figure can legitimately go negative — the portal accepts it, and it isn't a sign something's broken.

Doing this in CredHill

Open an invoice from View Invoices and use the ⋯ menu to raise a credit or debit note against it. A few things are deliberate:

• You get a checklist of the invoice's line items, nothing pre-selected — you tick what's being returned or adjusted, rather than starting from everything and having to remember what to delete.
• A ticked line's GST rate is locked to what the invoice actually charged, for the reason above. You can reduce its quantity, but not its rate.
• You can also add a line that wasn't on the original invoice — freight discovered later, a price escalation — with its own rate, since that's a legitimate ground for a debit note.
• The note gets its own numbering, separate from your invoices, and the original invoice's number and date print on it automatically.

Nothing about the original invoice changes. It's still exactly what you filed.

Common mistakes

1. Re-rating a copied line to today's GST slab. Covered above — the invoice's rate travels with the note, always.
2. Using the invoice number series for notes. Keep them separate, or your invoice sequence breaks.
3. Treating a debit note as informal. It's a GST document with the same Rule 53 requirements as a credit note — a WhatsApp message asking for more money isn't one.
4. Missing the 30 November deadline on a credit note and only noticing at annual-return time, when it's too late to claim the reduction.
5. Assuming the liability drops the moment you issue the note. Since October 2025, it depends on your buyer's side too — see above.

The short version

• Credit note — invoice was too high, reduces what you owe, has a declare-by deadline.
• Debit note — invoice was too low, increases what you owe, no deadline.
• Both reference the original invoice, run their own number series, and carry the original invoice's GST rate — never today's.
• Both are reported separately in GSTR-1 Table 9B, and net into GSTR-3B Table 3.1(a).
• Since October 2025, reducing your liability via a credit note depends on your registered buyer reversing the matching ITC.

Not tax advice. Section 34 has been amended twice in the last year, and the ITC-reversal and post-sale-discount changes in particular are new enough that practice is still settling. For anything beyond a straightforward return or under-billing, check with a chartered accountant before relying on the timing or the wording here.