When Legal Form and Economic Reality Drift Apart: Lessons from a Luxembourg Guarantee Case
If your company moves cash between its own entities through Luxembourg, a March 2026 ruling changed what an unwritten promise can cost you. A Luxembourg court found that when one group company agrees to stand behind another’s debts, it has to charge the same fee an unrelated guarantor would.
The reassessment window in Luxembourg is normally five years, but the law extends it to ten whenever a tax return was incomplete or inaccurate. If this guarantee was not considered in the transfer pricing, the returns connected are counted as incomplete, and the court allows authorities to reassess years already a decade old.
The company is then charged the guarantee fee they should have collected every year and never did, plus back-tax and monthly late-payment interest on each reopened year. The same court also refused to hand the tax office the group’s entire financing profit, and that refusal matters as much as the bill.
What the case was really about
Intercompany financing is just a group lending money to itself: one entity borrows while another lends or backs the loan, instead of everyone going to a bank. A guarantee is a promise by one of those entities to cover the debt if the borrower cannot. That promise has value, because the borrower gets cheaper or easier credit for having it. And the rule that governs deals between related companies is the arm’s-length principle: treat your own affiliates the way two unrelated businesses would treat each other. An outside party would never carry someone else’s credit risk for free, so a group company that does is supposed to charge a fee for it.
In the Luxembourg case, known publicly as “Holding Company AA,” a Belgian group ran its internal lending through a Luxembourg branch. A tax ruling let that branch deduct almost all of its interest income, on the basis that it carried very little risk. A separate letter, signed in March 2012 and never shown to the Luxembourg tax office, quietly put the credit risk on the group’s Luxembourg parent instead. Essentially, the parent carried that risk for years and never charged for it.
Why an old, unwritten letter reopened a decade of returns
Because the letter changed who really bore the credit risk, and because the tax office had never been told the letter existed, the court treated it as a “new fact” that rendered the original returns inaccurate. On that basis the authorities were entitled to reassess tax years 2012 through 2015, even though the earliest of those years was already a decade old.
What surfaced the letter at all was the group’s own inconsistency across borders. Belgium audited the Belgian company, concluded that the financing risk really sat in Luxembourg, and said so to the Luxembourg authorities in a routine exchange of information.
However, the group had relied on that same 2012 letter in Belgium to place the risk in Luxembourg, then left it undisclosed in the Luxembourg returns.
Picture a group that guarantees 500 million euros of internal loans. At a modest guarantee fee of around half a percent a year, that is roughly 2.5 million euros of income it should have recorded every year and never did. Reopen four years of that, then add Luxembourg’s late-payment interest of 0.6 percent a month running the whole time, and a guarantee no one priced turns into a seven-figure liability.
The part the company won
The tax office did not just want a guarantee fee. It tried to move the branch’s entire financing profit to the parent, arguing that whoever bears the risk should get the whole return. The court said no. Carrying credit risk, it held, is not the same as running a financing business, which means deciding who to lend to, setting the terms, and managing the money.
The parent lost even the fee, and the reason should worry any tax team. Its own transfer-pricing study admitted that an independent party would have charged a guarantee fee, then argued the promise was really just shareholder support that did not need paying for. The court rejected that argument as contradicted by the company’s own study.
What this means for a group like yours
The exposure is any letter, comfort note, or keep-well promise in which one entity quietly backs another’s borrowing and no fee changes hands. Plenty of groups have one sitting in a treasury folder, signed years ago for a lender or a rating agency and never run past the tax team.
The two leading Luxembourg commentaries on the case read it from opposite ends, and a group is exposed to both.
KPMG treats this judgment as a documentation mandate.
A group, on its reading, should be able to name which of its entities act as guarantors, state whether each one charges an arm’s-length fee, and, where one does not, explain why the promise genuinely confers no benefit worth pricing.
Bonn Steichen & Partners conclude that when the tax office over-reaches, the courts will trim the adjustment back to the guarantee fee owed and no further. But that cap only protects a group whose file already shows who carries the risk and who runs the financing, described the same way in every country that reads it.
The OECD’s 2020 guidance on financial transactions, which KPMG and BDO both note the Luxembourg court followed, offers several ways to price a guarantee, including the yield approach, the cost-of-funds approach, and an analysis of the credit-rating uplift the borrower gains from being backed. The judgment never disclosed which method set this fee. So “charge an arm’s-length fee” is the easy half to state and the contestable half to prove, because the number itself is what a tax office and a taxpayer will still argue over, and a file that has already done that work is the one that wins the argument.
How Exactera can help
Exactera’s transfer pricing specialists run a confidential, no-obligation review of a group’s intercompany financing, under mutual NDA, for companies that want to know whether any entity is carrying credit risk it never charged for. Send your intercompany agreements and a simple entity map to exactera.com/tp-review, and within two weeks you will have a prioritized read of where an undisclosed guarantee could reopen old years and what an arm’s-length fee would look like.
Sources
– KPMG. (2026). *Luxembourg TP: Guarantee fees in focus*. KPMG Luxembourg, May 22. https://kpmg.com/lu/en/insights/regulatory-updates/luxembourg-tp-guarantee-fees-focus.html
– Bonn Steichen & Partners. (2026). *Luxembourg transfer pricing case law: Undisclosed counter-guarantee subjected to TP adjustment*. BSP, May 15. https://www.bsp.lu/lu/publications/newsletters-newsflashes/luxembourg-transfer-pricing-case-law-und…
– BDO. (2026). *Luxembourg Administrative Tribunal rules that undisclosed counter-guarantee triggers transfer pricing adjustment*. BDO Global. https://www.bdo.global/en-gb/insights/tax/transfer-pricing/luxembourg-administrative-tribunal-rules…
– OECD. (2020). *Transfer pricing guidance on financial transactions: Inclusive framework on BEPS Actions 4, 8–10*. OECD Publishing. https://www.oecd.org/en/publications/2020/02/transfer-pricing-guidance-on-financial-transactions-in…
