How can you find out why there is a difference between the tax assessment and the taxx.lu result?

There may be a difference between the final result issued by the tax authority and the estimation provided by taxx.lu. In such cases, the tax authority usually adds an explanatory note at the bottom of the tax assessment, indicating the reason for the difference.

This information appears under the heading: « L’imposition diffère de la déclaration sur les points suivants »

If the tax authority has not provided an explanatory note, which is possible, you can, if you have selected a Plus or Premium package, contact taxx.lu at the following email address: help@taxx.lu.

We will then help you identify the source of this difference and, if necessary, assist you in drafting an appeal letter.

Documents to send for the review

To compare your tax return with your tax assessment notice, email us at help@taxx.lu with all the pages of the notice, including the “Décompte” (statement) section. You can see an example of the documents we need in our article What does the tax authority's tax statement look like?

We carry out the review before the three-month deadline for filing a complaint expires, so that you have enough time to file one if necessary. If we find that items in your tax return have not been taken into account correctly, we will draft the complaint letter for you and send it to you. Once we have reviewed all the documents, we will email you with details of the differences we have found.

Important deadlines

• Complaint: must be filed within three months of receiving the tax assessment notice.
• Payment: if you have tax to pay, it is due within one month of receiving the notice, to avoid interest or penalties.
• Refund: if you are due an additional refund after our review, the tax authorities will send you a second letter once they have processed the complaint.

Updated on: 16/10/2026