A credit note is issued by a supplier when the value of an earlier invoice needs to be reduced: goods are returned, a discount is given, or an invoice was overstated. Under GST, it reverses the corresponding tax, so both the supplier’s liability and the buyer’s input tax credit are adjusted.
Credit notes must be reported in GST returns and linked to the original invoice. The mirror document that increases an invoice value is a debit note.
Take an invoice of ₹10,000 with GST at 18%: ₹1,800 of tax, ₹11,800 in all. If goods worth ₹2,000 come back, the credit note is for ₹2,000 plus ₹360 GST — ₹2,360. On the supplier's books, sales returns are debited and the customer's account credited, and output tax falls by ₹360. The buyer mirrors this: the amount payable to the supplier drops by ₹2,360, and ₹360 of input tax credit must be reversed.
A distinction worth knowing is between a GST credit note and a purely commercial one. Only the supplier's credit note carries tax effect, and the tax reduction must be declared in returns within the statutory window following the end of the financial year of the original supply. After that window closes, a credit note can still be issued for the value — settling the account commercially — but without any GST adjustment.
The frequent slips are procedural. Suppliers reduce their liability but the buyer never reverses the matching credit, which surfaces in reconciliation notices. Credit notes get raised without reference to the original invoice, breaking the audit trail. And businesses sometimes cancel and re-issue invoices where a credit note was the correct instrument — once an invoice is reported, adjustment through a note, not deletion, is the discipline that keeps returns and books aligned.