How to issue a debit note under GST (with CGST Act 2026 rules)

A debit note is issued when the original invoice undercharged the customer — wrong rate, missed charges, MSMED interest. Get it wrong and you create reconciliation problems. Here is the exact process.

Step 1: Identify the right use case

Under-billing correction. Additional charges (freight, packing, MSMED interest). Tax rate correction (charged 5% but should be 12%). Don't use debit note for normal sales — that's a regular invoice.

Step 2: Reference the original invoice

Mandatory: original invoice number and date. Reason for debit note. New taxable value, new GST, new total. The relationship to the original invoice must be unambiguous.

Step 3: Use a separate debit note series

Keep your debit note numbering separate from invoice numbering. e.g. DN-001/24-25. This makes audit and reconciliation cleaner.

Step 4: Report in GSTR-1 of the issue month

Debit notes go in Table 9B of GSTR-1. The customer's GSTR-2B will reflect it in the same month so they can claim the extra ITC.

Step 5: Watch the time limit for tax-affecting debit notes

If the debit note affects tax payable in a particular invoice, it must be issued by November 30 of the year following the original invoice's financial year. After that the debit note is invalid for tax purposes.

Frequently asked questions