Credit note vs debit note: when to raise which

A customer returns half a delivery. A dealer was billed at last month's rate, not this month's. A freight charge was left off the invoice. Each of these is a normal event in trade — and each is handled not by editing the original invoice, but by raising a separate note. Getting the choice right — credit note or debit note — keeps your customer ledger correct and your GST return clean. Get it wrong, or handle it by quietly editing an invoice, and the audit trail breaks.

This guide explains both documents in plain terms: what each is, exactly when to raise which, how GST treats them, and a worked example you can follow. If you want the wider context — the whole sale-to-accounts flow and where notes fit — see the pillar guide, What is GST billing software?. In the product, this is Credit & Debit Notes.

1. What a credit note is

A credit note is a document a seller issues to reduce the amount a customer owes after a tax invoice has already been raised. It says, in effect, "we billed you for X, but the correct amount is less, so here is the difference credited back to you." Because it lowers the taxable value, it also reverses the corresponding GST that was charged.

Crucially, a credit note is not an edit to the original invoice — the invoice stands, and the credit note is a separate, numbered document that references it. That reference is what keeps the trail intact: anyone can see the original sale, and the adjustment made to it, side by side. The most common trigger is a sales return, where a good system raises the credit note automatically against the dispatch and invoice.

2. What a debit note is

A debit note is the mirror image: a document that increases the amount a customer owes after the invoice. It says "we billed you for X, but the correct amount is more, so here is the extra debited to your account." Because it raises the taxable value, it also adds the corresponding GST.

Like a credit note, a debit note references the original invoice and is reported in your GST return — effectively as an additional charge on that sale. It is the right tool whenever the invoice under-stated the value: a wrong (lower) rate, an understated quantity, or a charge such as freight that was missed. A seller's debit note to a customer is distinct from a customer's own debit note to a supplier — here we mean the note you raise on your customer.

3. Credit note vs debit note at a glance

Side by side, the difference is simple to hold in mind:

Both are formal documents; neither is an edit to the invoice. That single discipline — adjust with a note, never overwrite the invoice — is what a manual template most often gets wrong, and what a real billing system enforces. See Credit & Debit Notes.

4. When to raise a credit note

Raise a credit note whenever the value of a supply falls after the invoice. The common cases:

• Sales return. The customer sends goods back — damaged, wrong item, or surplus. The credit note reverses the returned value and its GST. This is the classic case, and good software raises it automatically against the dispatch and invoice.
• Short supply. You billed for 100 units but shipped 90. A credit note corrects the 10-unit over-billing and its GST.
• Deficiency or quality issue. The goods or service fell short of what was billed, and a value reduction is agreed.
• Price reduction after billing. A post-invoice discount or a corrected (lower) rate agreed with the customer.
• Invoice cancellation. The whole sale is being reversed — the credit note (or a cancellation that releases the billed quantity) unwinds it cleanly so the dispatch can be re-billed correctly if needed.

5. When to raise a debit note

Raise a debit note whenever the value of a supply rises after the invoice. The common cases:

• Under-charge. The invoice value was simply too low — a data-entry slip or an omitted item — and needs topping up.
• Rate difference. The agreed or revised rate is higher than what was billed; the debit note recovers the difference and its GST.
• Understated quantity. You shipped and should have billed 110, but the invoice said 100; the extra 10 is debited.
• Additional charge. Freight, packing, insurance or a handling charge that was agreed but left off the original invoice.

In every case the debit note references the original invoice and carries its own GST, so both your books and the customer's records line up. If you find yourself repeatedly raising debit notes for the same missed charge, that is usually a sign the charge should be built into the invoice template — something GST tax invoicing with configured charge heads handles up front.

6. How GST treats credit and debit notes

Under GST, both notes are formal documents with specific handling:

• Both must reference the original tax invoice. A note that does not tie back to an invoice cannot be matched, and that mismatch is exactly what triggers scrutiny.
• A credit note reduces the taxable value and the output GST you had charged; a debit note increases them.
• Each is reported in your GST return for the period in which it is issued, adjusting your tax liability up (debit note) or down (credit note) accordingly.
• The customer's records adjust to match — their input credit reduces on your credit note and increases on your debit note — which is why the reference and the numbers must be exact.

Because the adjustment has to reconcile against the original invoice and appear correctly in the return, doing this by editing the invoice — or in a spreadsheet — is where errors and disputes begin. Software that links every note to its invoice and posts it to your accounts as the matching Cr/Dr note keeps the whole chain clean; see the billing-to-accounts guide.

7. A worked example

Take an illustrative original invoice: a distributor billed a dealer for 100 valves at ₹200 each = ₹20,000, GST 18% (same state, so CGST 9% + SGST 9% = ₹3,600), invoice total ₹23,600.

Case A — sales return (credit note)

The dealer returns 15 defective valves. You raise a credit note against the original invoice:

The dealer's outstanding falls by ₹3,540, and your output GST for the period reduces by ₹540.

Case B — rate difference (debit note)

Separately, you discover the agreed rate was ₹210, not ₹200 — an under-charge of ₹10 on all 100 valves. You raise a debit note:

The dealer's outstanding rises by ₹1,180, and your output GST for the period increases by ₹180. Both notes reference invoice INV/2026-27/00042, so the original sale and each adjustment sit together in the ledger and the GST return.

8. How Fast Billing Software handles notes

Fast Billing Software, built in Pune by Improsys under the Fast Technology brand and available cloud and on-premise, keeps notes tied to invoices and to your accounts automatically:

9. Frequently asked questions