Luxembourg: Luxembourg tax authorities release circular on the use of a foreign functional currency for tax purposes

International Tax Review is part of Legal Benchmarking Limited, 1-2 Paris Garden, London, SE1 8ND

Copyright © Legal Benchmarking Limited and its affiliated companies 2026

Accessibility | Terms of Use | Privacy Policy | Modern Slavery Statement

Luxembourg: Luxembourg tax authorities release circular on the use of a foreign functional currency for tax purposes

merle.jpg

Samantha Merle

In a recent circular, the Luxembourg tax authorities defined the rules applicable upon request to undertakings with a share capital and accounts in the same foreign currency, which wish to determine their taxable income by simply converting their commercial result in foreign currency into EUR. The release of this circular is motivated by the fact that strict application of the Luxembourg valuation rules to these undertakings may in certain cases create artificial taxable exchange profits, which appear when preparing a tax balance sheet in EUR and thus do not reflect the economic reality. To avoid this kind of situation, the tax authorities have defined the rules and conditions to apply the foreign functional currency for tax purposes. We present the main aspects. The possibility to use the functional currency applies, upon request, to undertakings with share capital and accounts in the same foreign currency. Once an undertaking has opted for the regime, it will have to use its functional currency as long as its share capital remains denominated in this currency. A request has to be filed with the Luxembourg tax authorities at the latest three months before the end of the tax year in which the undertaking intends to benefit from the regime (September 30 at the latest, if the tax year corresponds to the calendar year).

The commercial result in foreign currency is increased by the amounts which are not tax deductible for tax purposes (in foreign currency), decreased by the amounts exempt (in foreign currency as well) and then converted into EUR based on exchange rates determined by the European Central Bank. The taxpayer can choose between the year-end rate or the average rate of the year. Once the choice has been made, the taxpayer will have to apply the rate chosen to all future tax years. This exchange rate will apply to all amounts in foreign currency as well as to tax losses of previous years which are carried forward and will be converted at the rate of the tax year for which they are taken into account. The determined amounts in EUR are then reported in the tax returns of the undertaking and the related tax assessments issued by the tax authorities are in EUR as well.

To check whether a shareholding qualifies for the participation exemption regime according to which dividends, liquidation proceeds and capital gains can be exempt under certain conditions, the value of the participation (which must reach a certain value in EUR for the exemption regime to apply) has to be converted into EUR by using the historical exchange rate (the rate as of the date of acquisition of the participation). This approach is justified, as the participation might otherwise qualify for the participation exemption regime in one tax year and no longer qualify in another, if the exchange rate varies significantly from one year to another.

To determine the amount of minimum CIT due by Luxembourg companies, reference has to be made to the total balance sheet, converted into EUR by using the exchange rate applicable to the related tax year (year-end exchange rate or average rate of the year).

Lastly, the circular clarifies the rules applicable for municipal business tax (MBT) and net wealth tax (NWT) purposes and the implications on the determination of the amount of NWT reduction, which is available under certain conditions to taxpayers. Furthermore, it expands on the rules which will apply during the transitory year for a taxpayer who until now has prepared a tax balance sheet in EUR and now opts for the future use of the functional currency for tax purposes.

Samantha Merle (samantha.merle@atoz.lu)

ATOZ – Taxand Luxembourg

Tel: +352 26 940 235

Website: www.atoz.lu

more across site & shared bottom lb ros

More from across our site

A new focus on early intervention and increased AI use is transforming how tax authorities are approaching TP audits, though capacity-constrained jurisdictions risk falling behind
The French administration has used AI to detect undeclared swimming pools and verandas but always includes a human in the loop, the AI in Tax Forum heard
The UK tax authority’s deputy director of large business also reassured taxpayers that HMRC will not ‘nitpick’ returns
Sucafina’s tax chief was speaking at the ITR Pillar 2 Forum in London alongside experts from HMRC and other organisations
India’s Supreme Court rattled cross‑border structuring with its Tiger Global ruling. Subsequent rule changes narrowed the impact, but significant risks around GAAR, substance and treaty access persist
The UK-based big four spin-off firm has hired Marc Lien, who declared that most AI in professional services today is ‘cosmetic’
Projected revenue losses and exemption requests are harming the project’s capability and viability
HMRC secured lengthy prison sentences in a major payroll VAT fraud case, while law firms announced tax promotions and hires
Significant changes include an update to profit markers and an alteration to how an ‘inbound distributor’ is defined
ITR sat down for a pre-event interview with Tim Zech, WTS Germany, and Jeff Soar, WTS UK, keynote speaker at next week’s ITR AI in Tax Forum 2026 in London
Gift this article