Debit note format when you under-billed the customer
The supplementary document that raises the value or tax of an invoice already issued — how it works, what it must carry, and why its timing rules differ from a credit note.
Create a debit note freeA debit note is the mirror image of a credit note. Where a credit note reduces an invoice, a debit note increases it — the rate was billed too low, a quantity was under-charged, freight was left out, or a price revision was agreed after the bill went out.
Under GST it is a supplier-issued document, sometimes called a supplementary invoice, and it carries tax exactly like the invoice it corrects. Unlike a credit note, there is no cut-off for issuing one; the time pressure sits with the buyer, whose right to claim the extra credit is tied to the debit note's own date.
What this format must carry
Every field below, with whether it is mandatory and what it is for.
| Field | Required | Notes |
|---|---|---|
| The words "Debit Note" | State it on the face of the document so the buyer books it as an addition, not as a fresh sale. | |
| Debit note number and date | Consecutive serial of up to 16 characters, unique for the financial year, in a separate series such as DN/2627/0004. | |
| Supplier name, address, GSTIN | Your registered details, identical to those on the original invoice. | |
| Recipient name, address, GSTIN | The buyer from the original invoice, so both sides can match the adjustment in their returns. | |
| Original invoice number and date | The mandatory link back to the invoice being corrected. | |
| Reason for the debit note | Rate under-charged, short billing, quantity revision, freight or packing missed, price escalation as per contract. | |
| Additional taxable value | Only the incremental amount, not the revised total — the original invoice already carries the rest. | |
| Tax rate and amount | Same head and rate as the original supply. Intra-state stays CGST plus SGST; inter-state stays IGST. | |
| Signature or digital signature | Signed by the supplier or an authorised person, or digitally signed where issued electronically. |
Guidance only. GST rules and rates change by notification — confirm the requirements for your business on the CBIC portal or with your CA.
When to issue a debit note
Section 34 allows a debit note where the taxable value or the tax charged on an invoice is found to be less than what was actually payable. In everyday trade that means a wrong rate, an item billed short, a discount applied that was never agreed, or contractual price escalation settled after delivery.
One thing a debit note is not: a substitute for a fresh invoice on a new supply. If you are supplying additional goods, raise an invoice. A debit note only corrects the value or tax of a supply already invoiced.
Why the timing rules differ from a credit note
A credit note reduces your liability, so the law puts a deadline on it — reported by 30 November following the financial year of the supply. A debit note increases your liability, so there is no deadline on issuing one; the government is in no hurry to stop you paying more tax.
The clock instead runs for your buyer. Input tax credit on a debit note is linked to the financial year of the debit note itself, not of the original invoice, so the buyer generally has until 30 November following the debit note's own financial year to claim it. Issue late and you strand your customer's credit — which usually means an argument about who absorbs the tax.
Practical points
Debit notes get reported in your outward supply return in the period they are issued, and the extra tax is paid with that period's liability. Keep a separate series, keep the original invoice reference on every note, and never adjust the tax head — a supply that was intra-state stays intra-state even if the buyer has since shifted address.
If the buyer sends you a document titled "debit note" for a return of goods, that is their internal accounting entry. The GST effect comes from a credit note issued by you. RetailDek's free invoice generator handles both supplementary documents from the original bill.
Skip the template — generate it
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Create a debit note freeDebit Note Format — FAQs
A debit note increases the value or tax of an earlier invoice; a credit note reduces it. Both are issued by the supplier under Section 34, both must reference the original invoice, and both carry tax at the original rate and head.
Make it the output, not the chore
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