How to Cancel or Correct an Invoice as Self-Employed in Luxembourg

You issued an invoice to a client, reported it on your VAT return, and now you need to cancel it — or reduce the amount. What do you do?

The short version: never delete an invoice. Issue a credit note (avoir) instead, and correct your VAT return if needed.

The good news: if you act quickly, corrections are straightforward. The only real complexity is for quarterly VAT filers when a credit note falls in a different quarter than the original invoice.

Why you might need to cancel an invoice

Common reasons:

• Error on the invoice — wrong amount, wrong client details, wrong VAT rate
• Service not delivered — you invoiced in advance but the work was never completed
• Client dispute — you agreed to reduce the price or cancel the engagement
• Duplicate invoice — you accidentally issued the same invoice twice
• Agreed discount after the fact — a retroactive price reduction

Each of these is a valid reason to issue a credit note. The important thing is to document why. The guides on what an invoice must show and on late supplier invoices are gathered under invoices and e-invoicing in Luxembourg.

How to cancel an invoice: issue a credit note

Never just delete an invoice from your records. Once an invoice is issued, it exists — deleting it breaks your audit trail and can cause serious problems in a tax audit.

Under the Luxembourg VAT Law, any document that modifies an invoice in a specific and unequivocal way is itself a new invoice. That means you can’t fix things with an informal email like “please ignore line 2 of invoice 2026-014” — the moment you write something that clearly changes the original, you’ve legally issued a new invoice and it must carry at least a simplified invoice’s mentions: the date, your identity, the VAT impact, and a specific reference to the original with the mentions it changes (article 63 §10 and §11). The only safe way to correct an invoice is a proper credit note.

Instead, issue a credit note (avoir, also called a note de crédit):

• Full cancellation — credit note for the entire amount, referencing the original invoice
• Partial correction — credit note for the difference (e.g., price was reduced from 1,000 EUR to 800 EUR, credit note for 200 EUR)

Deadline for issuing a credit note

The same rule as for invoices: you must issue a credit note by the 15th of the month following the event that triggers it (e.g., the cancellation agreement, the returned goods, or the agreed price reduction). This is the same deadline that applies to regular invoices under Luxembourg VAT law.

What does this mean in practice? The credit note is always dated with the current date — the date you actually issue it. This means if you agree to cancel an invoice on January 5, 2026, the credit note is dated January 2026, even if the original invoice was from December 2025.

This is why there is almost never a “previous year” problem with credit notes. A cancellation agreed in January is a January change: its credit note goes on a return of the new year, even for a December invoice. A change that happens in December belongs to December’s period, even if you issue the credit note by January 15 — so issue it before you file that return.

You might be tempted to backdate a credit note to December to keep everything in the same year. Be careful with this. Backdating beyond the 15-day window is not correct under the law. And even if you could, consider your client: if they file VAT annually and have already included your original invoice in their annual return, your backdated credit note forces them to file a correction. If you think backdating is necessary, talk to your client first — and consult your accountant.

What a credit note must include

• A clear reference to the original invoice number
• The date of the credit note
• The reason for the correction
• The amount being credited (including VAT if applicable)
• The same VAT rate as the original invoice — even if VAT rates have changed since then
• Your name and business details, as on a regular invoice — though a credit note may be a simplified invoice, which needs fewer of them (article 63 §10)

A credit note is essentially a “negative invoice.” It reduces your revenue and output VAT by the credited amount.

VAT: how to handle the credit note

A credit note is reported on the VAT return for the period in which the change it records happens — the cancellation, the returned goods, the agreed price cut — not the period of the original invoice. The regulation of 21 December 1979 on adjusting the taxable amount has the adjustment made by the end of that return period at the latest (article 2). Usually that is the period in which you issue the credit note. This is the key rule.

In practice, most self-employed people file VAT either quarterly or annually. Here’s what to do in each case.

If you file VAT quarterly

This is where most of the real scenarios happen:

Credit note in the same quarter as the original invoice
Your quarterly return is not filed yet. Simply include the credit note — it reduces your output VAT. Nothing else to do.

Credit note in a later quarter, same year
For example: original invoice was in Q1, credit note is in Q2. Include the credit note in your Q2 return. It reduces your Q2 output VAT. You do not need to go back and correct Q1 — declaring the credit note in the next quarterly return is the correct approach.

Credit note in Q1 of the next year (e.g., January credit note for a December invoice)
If the cancellation or price cut is agreed in January, the credit note goes on your Q1 return of the new year. It’s a new-year return, but the process is the same: it reduces your Q1 output VAT. No corrective return needed for the previous year. If the change happened in December, it belongs on your Q4 return, even when the credit note is issued by January 15.

Credit note much later, and the annual VAT return for that year is already filed
The same rule applies: the credit note goes on the return for the quarter in which the change happens, and the earlier year’s returns stay as they are. A corrective VAT return (see below) is for an error in a return you filed, not for a later credit note.

Practical tip: If you know a credit note is coming, try to issue it before your next quarterly return. This keeps things clean — one return, one adjustment, done.

If you file VAT annually

Annual filers rarely have a correction problem. Your annual VAT return for 2025 is due before March 1, 2026, the deadline Guichet.lu on filing VAT returns sets for annual-only filers. A credit note goes in the return of the year in which the change happens: a cancellation agreed in January 2026 for a 2025 invoice goes in your 2026 return; one agreed in December 2025 goes in your 2025 return, even if you issue the credit note in January.

A corrective return is for fixing an error in a return you have filed, not for a credit note.

How to file a corrective VAT return (when needed)

If you do need to correct an error in a previously filed return:

1. Log into eCDF (via MyGuichet.lu or eTVA)
2. Go to Submitted returns
3. Use the Copy function on the original return for the affected period
4. Correct the figures that were wrong
5. Submit — the corrected return replaces the original

You have 5 years from 31 December of the year the VAT relates to (articles 81 and 82 of the VAT law).

If the correction lowers VAT you already paid to AED, the corrective return will create a VAT credit. This credit is automatically carried forward to the next period, or you can request a refund.

Intra-EU transactions

If the cancelled invoice was for an intra-EU supply:

• The credit note goes in the recapitulative statement (état récapitulatif) for the period in which you send it to the customer, under that customer, with a reference to the statement that held the original invoice — as the regulation of 1 December 2009 on the recapitulative statement sets out (articles 6 and 7)
• The corrections part of a statement is only for fixing an error or omission in a statement already filed

Income tax: almost never a problem

Income tax is filed once per year, and the deadline is generous: your 2025 income tax return (Form 100, the déclaration d’impôt) is due by December 31, 2026.

This means any credit note issued in 2025 or 2026 (before you file) is simply netted against the original invoice in your records. Your tax return shows the correct net revenue. No correction needed.

The only scenario where you’d need to correct income tax is if you’ve already filed your Form 100 and then issue a credit note:

• Within 3 months of your tax assessment’s notification — file a written objection (réclamation) with the ACD, as Guichet.lu on contesting an ACD decision states
• After those 3 months — the tax office has discretionary authority and may or may not accept the correction

In practice, this almost never happens. You have until December 31 of the following year to file, and most credit notes are issued well before then.

Scenarios at a glance

Key contacts

Practical tip: Always keep your credit notes numbered sequentially (e.g., CN-2026-001) and cross-referenced to the original invoice. This makes your records clean for audits and makes corrections straightforward.