Luxembourg Administrative Court clarifies what qualifies as a tax claim against tax assessments

A recent Administrative Court decision overturns a 2025 ruling of the Administrative Tribunal and confirms a substance‑over‑form approach to the qualification of tax claims under Luxembourg procedural law

On 12 February 2026, the Luxembourg Administrative Court (Cour administrative, No. 53399C) overturned the judgment of the Administrative Tribunal (No. 49156) of 9 July 2025, which addressed the distinction between a modification request under § 94 of the General Tax Law of 22 May 1931 (Abgabenordnung, AO) and a tax claim under §228 AO.

The Tribunal had found that a taxpayer letter, sent after provisional assessments issued under § 100a AO and announcing forthcoming amended accounts and an amended tax return, could not be regarded as a tax claim, but at most as an out-of-time request for modification under § 94 AO. On that basis, the Tribunal considered that no valid prior claim had been filed and declared the taxpayer’s judicial appeal inadmissible.

The Administrative Court disagreed adopting a more flexible interpretation of what constitutes a tax claim.
 

Background

A Luxembourg company filed its FY 2019 tax returns on 1 July 2021. On 14 July 2021, the tax authorities issued provisional assessments for corporate income tax (CIT), municipal business tax (MBT), and net wealth tax (NWT).

By letter dated 24 August 2021, the company stated that its 2019 annual accounts did not reflect its economic reality and failed to present a true and fair view. It further indicated that both the accounts and the corresponding tax return would be amended.

On 11 November 2021, the company submitted amended 2019 annual accounts and amended tax returns. The tax authorities treated the 24 August 2021 letter as purely informative and the amended filings as a request for modification under § 94 AO, submitted out of time. As the three‑month deadline following the 14 July assessments had expired, the request was rejected. The company subsequently lodged a judicial appeal, which the Tribunal declared inadmissible.
 

Administrative Court’s key findings

Broad interpretation of “claim” (§ 228 and § 249 AO)

The Court recalled that, pursuant to §249 AO, a legal remedy is deemed to have been validly lodged where it is apparent from the document that the taxpayer considers itself aggrieved and seeks a review. An incorrect designation of the remedy is, in this respect, immaterial.

It confirmed that:

• The concept of a claim must be interpreted broadly, in line with a substance‑over‑form approach;
• The tax authorities are required to assess the overall content and context of the communication, rather than relying solely on its formal wording or label;
• The fact that the letter is addressed to the tax office, rather than directly to the director, does not prevent its qualification as a claim.
   

The letter contained a grievance, completed by the amended return

Contrary to the Tribunal, the Court held that:

• By stating that the 2019 accounts did not present a true and fair view, the company implicitly challenged the reliability of the tax bases underlying the assessments of 14 July 2021 and thus expressed a grievance, regardless of the fact that those assessments were provisional within the meaning of § 100 AO.
• The announcement of amended accounts and an amended tax return necessarily implied a request for reassessment.

The Court further held that neither § 94 AO nor § 228 AO requires a fully detailed motivation from the outset. The amended 2019 tax return and revised annual accounts filed on 11 November 2021 could validly supplement the initial letter by specifying:

• The concrete corrections, namely the impairment of a participation and of a receivable relating to a UK mining company; and
• Their financial impact, notably the conversion of a profit into a loss and of positive net wealth into negative net wealth.

Taken together, the letter of 24 August (filed within the applicable three‑month period), and the amended filings of 11 November 2021 had to be regarded as constituting a claim within the meaning of § 228 AO.
 

Distinction between § 94 AO and § 228 AO maintained

The Court reaffirmed the distinction between a request for modification under § 94 AO and a claim under § 228 AO, as well as the respective consequences in the present case:

• § 94 AO: A request for modification addressed to the tax office, limited to specific points.
• § 228 AO: A claim addressed to the director, triggering a full review of the assessment and potentially leading to a revision in pejus.

The Court agreed with the administration that, by November 2021, the three-month period of modification under § 94 AO had expired and the assessments could no longer be amended on that basis. However, once a grievance had been expressed and the § 94 AO window was closed, the only effective procedural avenue was a claim. In that context, the time limit for submitting additional supporting documents does not expire until the Director has rendered a decision. The tax authorities should therefore have treated the taxpayer’s submissions as a claim and referred the matter to the Director.
 

Less stringent corporate signature requirement for a claim than for court proceedings

The State argued that the letter could not constitute a valid claim, as it had been signed by only one manager, whereas the company’s articles required joint signatures for acts beyond day‑to‑day management. The Court rejected this argument, emphasizing that:

• § 249 AO only requires that the author of the claim be identified; it does not impose the same formal representation requirements as those applicable to court proceedings;
• The company was clearly identified in the letter, and the signature of one of its managers was sufficient to meet the validity requirements of a claim.
   

Practical takeaway

In its 2026 decision, the Administrative Court adopts a flexible and pragmatic interpretation of the claim provisions of the AO. It confirms that relatively concise correspondence, when read in conjunction with subsequent, more detailed submissions, may suffice to trigger the claim procedure, provided that the taxpayer’s intention to challenge the assessment can be clearly inferred from the overall context and that additional supporting documents are submitted before the Director issues a decision.

Nevertheless, as a matter of best practice, taxpayers should file a detailed and fully substantiated claim from the outset in order to minimize procedural risks.