Corporate tax return in Luxembourg: CIT, MBT and net wealth tax.

Who must file a corporate tax return?

Any resident capital company in Luxembourg (SARL, SA, SOPARFI, etc.) is in principle required to file an annual tax return each year covering corporate income tax, municipal business tax and net wealth tax. The return is prepared from the approved annual accounts.

Some vehicles benefit from specific regimes (for example the SPF, exempt from direct taxes but subject to subscription tax). We determine your exact obligations based on the company's form and activity. An individual's return (form 100) is a separate filing, covered on our Luxembourg tax return page.

How to file a company's tax return in Luxembourg?

The return is filed electronically via MyGuichet.lu and the eCDF platform, on the "modèle 500" form family. It restates the accounting result, the tax adjustments (depreciation, provisions, non-deductible expenses, loss carry-forwards) and the net assets used as the base for net wealth tax.

We prepare the return from your accounting, apply the relevant regimes (participation exemption where applicable) and file on time. You keep a single point of contact from bookkeeping through to tax filing.

What is the corporate tax rate in Luxembourg?

The aggregate corporate tax rate in Luxembourg City is about 23.87% as of 1 January 2026: corporate income tax of 16%, increased by a 7% employment-fund surcharge, plus the municipal business tax of 6.75%. Municipal business tax varies by municipality.

On top of this comes net wealth tax (NWT), at 0.5% of net unitary value, with a minimum net wealth tax. The effective rate actually borne depends on applicable exemptions (notably the participation exemption for holdings). We compute your real burden case by case.

Net wealth tax and minimum net wealth tax

Net wealth tax is levied on the company's net unitary value at 0.5%. Even without profit, companies are in principle liable for a minimum net wealth tax. Since tax year 2025 it depends solely on the balance-sheet total: EUR 535 up to EUR 350,000, EUR 1,605 up to EUR 2,000,000, and EUR 4,815 above. The former test based on the share of financial assets was repealed by the law of 20 December 2024.

This minimum tax is a point of attention for holdings and low-activity structures. We factor it in from the return computation and into the advances follow-up.

Advances, deadlines and tax assessments

The return is filed by 31 December of the year following the tax year: the return for financial year 2025 is due by 31 December 2026. This rule has applied since tax year 2022 for corporate income tax, municipal business tax and net wealth tax (ACD, "Filing deadlines"). CIT advances fall due on 10 March, 10 June, 10 September, 10 December; municipal business tax and net wealth tax advances on 10 February, 10 May, 10 August and 10 November. Each advance is set in principle at one quarter of the tax resulting from the last assessment and can be revised on a reasoned request.

We track your deadlines, adjust advances to avoid cash-flow shocks, review tax assessments and lodge a claim in case of an assessment error. The mechanism is detailed in our article on quarterly tax advances.

What does a company risk by filing its return late?

Three sanctions add up. The tax office may set a tax supplement of up to 10% of the tax assessed (§ 168 of the General Tax Law). It may then issue a formal notice followed by a penalty payment whose amount, announced in writing, depends on the seriousness of the delay (§ 202). Finally, where no return is filed, it must assess the tax ex officio by estimate (§ 217).

These three paragraphs belong to the General Tax Law (AO); the mechanisms and percentages are described by the ACD on its page "Prélèvements supplémentaires en cas de non-observation des délais de déclaration et de paiement", which does not cite the paragraph numbers. The estimated base is almost always higher than the actual result.

An assessment issued ex officio is challenged by a claim to the director of the ACD within 3 months of notification (§ 228). After that deadline it becomes final even if the estimate is clearly excessive. Late payment adds late interest of 0.6% per month on the balance due, including on the supplement.

If several years are open, the regularisation of late tax filings rebuilds the accounts and files the returns in deadline order, before the authority assesses ex officio. If a letter from the ACD has already arrived, tax audit assistance prepares the answer within the time allowed and, where needed, the claim.