What Is a Debit Note (Debit Memo)?
A debit note is a document that adjusts an amount already invoiced, and the confusing part is that the term is used in two directions. A seller can issue one to charge a customer more than the original invoice did; a buyer can issue one to claim a credit from a supplier.
This guide explains both uses, what a debit note contains, how it differs from a credit note, and when a new invoice is the better tool. Terminology and tax treatment vary by country, so check local practice before relying on either usage.
Seller-issued debit notes: charging more
If you undercharged on an issued invoice — you missed a line, applied the wrong rate, or shipped more than you billed for — you can't edit the original. In some countries the correction is issued as a debit note that references the original invoice and adds the difference.
Some tax systems formally recognize debit notes as the way to increase the tax on a sale after invoicing, with required contents much like a credit note's. Elsewhere, the same job is done with an ordinary additional invoice for the difference.
Buyer-issued debit notes: claiming a credit
In other businesses, particularly in trade and manufacturing, the buyer issues the debit note. It tells the supplier the buyer is reducing what they owe — for goods returned, short-delivered, or overcharged — and asks the supplier to issue a matching credit note.
Here the debit note is a request and a record on the buyer's side. The supplier's credit note is usually what formally reduces the invoice.
What a debit note contains
Whichever way it runs, a debit note should carry its own number and date, both parties' details, a reference to the original invoice, the reason for the adjustment, and the amount. If tax applies, show the tax adjustment separately, just as the original invoice did.
For example, a seller's debit note DN-004 referencing invoice INV-118 might add 20 units at $15 that were shipped but never billed, for $300 plus tax. At a 10% tax rate, DN-004 asks for $330, and INV-118 stays exactly as it was issued.
Debit note vs credit note
A credit note is issued by the seller and reduces what the customer owes. A seller's debit note increases what the customer owes, while a buyer's debit note records a reduction the buyer is claiming, which the seller normally answers with a credit note.
If that sounds tangled, hold on to the anchor: an invoice is never edited after it's issued. Every change, up or down, is a new numbered document that points back to it.
When to issue a new invoice instead
If the extra work or goods are genuinely a new sale, a new invoice is usually cleaner than a debit note. Keep debit notes for corrections to the original transaction — wrong prices, missed charges, quantity differences — and follow whatever your local tax rules require.