A supplier sends you a “debit note” for €120. Or you read the term somewhere and wonder whether you should be issuing them. The honest answer for most freelancers: almost never.
Here’s what a debit note is, and why a credit note usually does the job instead.
What is a debit note?
A debit note is a corrective document that increases the amount owed on an invoice that was already issued. You use it when the original invoice stays valid but you need to add to it — for example, late-payment interest, or a small extra charge agreed afterwards.
It’s the mirror image of a credit note: a credit note reduces what’s owed; a debit note increases it. Either way, the document references the original invoice — it can’t stand alone.
The rule of thumb (this is the part that matters)
There’s one simple test for which document to use:
- The original invoice needs replacing (wrong amount, wrong NIF, the job was cancelled) → cancel/void it and issue a new, correct one. This is the common case. (For a wrong amount, that’s typically a credit note + new invoice; for a wrong NIF/date/number, it’s the Anular function — see “What a note can’t do” below.)
- The original invoice is correct but you need to add an amount to it → issue a debit note for just that extra amount.
For most freelancers, almost every correction falls into the first bucket. That’s why, in practice, you’ll reach for a credit note and a fresh invoice — not a debit note. The credit-note-then-reissue method is cleaner: one cancellation, one new invoice, no ambiguity about what the client owes.
Not sure which document to issue in the first place? See the guide on which document to give each client.
Debit note vs credit note
- Increases what the client owes
- Original invoice is correct — you just add a charge
- Reasons: late-payment interest, an agreed extra
- How often a freelancer uses it: rarely
- Reduces or cancels what the client owes
- Original invoice is wrong or cancelled — replace it
- Reasons: wrong amount, refund, return, cancellation
- How often a freelancer uses it: often
Both are corrective documents, must be issued in AT-certified software, and always reference the original invoice.
The rare cases where a debit note is the right tool
A freelancer would genuinely need a debit note when the goal is to add value to an invoice that’s otherwise correct:
- Late-payment interest (juros de mora). The client pays late and your contract allows interest. The original invoice is fine — you just add the interest with a debit note referencing it.
- A small extra agreed afterwards. The client asks for a minor add-on and you both agree to attach it to the original transaction rather than open a new invoice.
In each case the original invoice stays as it is — the debit note sits on top and raises the total:
In the Portugal context
A nota de débito is a full tax document. Like invoices and credit notes, it must be issued through AT-certified invoicing software, with its own sequential numbering and an ATCUD code, and it’s reported to the tax authority (AT). If the original carried VAT, the debit note carries VAT too — and it changes the VAT you hand over in your periodic declaration.
What a note (debit or credit) CANNOT do
These documents adjust the financial value of an invoice — they don’t rewrite its details. So there are things no note can fix:
- They can’t change the client’s NIF. A note adjusts the value of a transaction (Article 29 of the CIVA ties corrective documents to changes in the taxable amount or the tax) — it doesn’t fix identifying data. If you issued the invoice to the wrong NIF, it went to the wrong entity, so the fix is to cancel the transaction (the Anular function, while it’s still available) and issue a new invoice with the correct NIF. If the cancellation window has already closed, check the exact procedure with your accountant or the AT before acting — don’t assume a note will fix it.
- They can’t change the original invoice’s date, number, series or ATCUD. Those are immutable. The note has its own date and numbering, always later.
- They can’t fix a wrong VAT rate by themselves in practice. If you applied the wrong rate, the cleanest fix is to cancel the invoice and reissue it with the correct rate — most invoicing tools (and the portal) only let you enter quantity and price, so there’s no clean way to register a standalone rate correction. If you charged too little VAT, fixing it is mandatory (Article 78(3) of the CIVA); don’t sit on it.
FAQ
Can I just reissue a fatura-recibo I filled in wrong? You can: cancel the wrong one and issue a new, correct one. Alternatively, issue a credit note that voids it and then the new invoice. Either path is valid — what you can’t do is edit or “ignore” the original.
Does the credit note show as a negative amount on the portal? Not always the way you’d expect. The portal often won’t let you enter a “−X” value directly; instead, you register the note referencing the invoice and reducing the relevant line(s). The end effect is the same — the original is corrected — but the way you fill it in can be confusing at first.
I applied the wrong VAT rate — what do I do? Fixing it is mandatory if you charged too little (Article 78(3) of the CIVA). In practice the simplest path is to cancel the wrong invoice and reissue it with the correct rate, because invoicing tools let you enter quantity and price but not a clean standalone rate adjustment. If in doubt, check the exact steps with your accountant before the deadline.
✅ In summary
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A debit note increases what a client owes; a credit note reduces it. Both reference the original invoice and must be issued in AT-certified software.
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As a freelancer you’ll rarely issue a debit note. To fix a wrong invoice (wrong NIF, wrong amount, wrong VAT rate), the standard move is to cancel it — a credit note that voids it, then a new correct invoice. A debit note is the right tool only when you need to add value to an invoice whose base is already correct: late-payment interest or a small agreed extra.
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With FIZ corrective documents are one click — the system references the original invoice automatically, handles the ATCUD and numbering, and adjusts your quarterly VAT without manual maths.
