Fiscal unity in Luxembourg: consolidating your group's corporate tax

In short. Fiscal unity, or tax consolidation, lets a group of Luxembourg companies add up its members' results and be taxed only on the balance. A loss in one company then wipes out a profit in another, within the same year. The regime, set out in article 164bis of the income tax law, requires holding at least 95% of the capital, a commitment of at least 5 years and an application filed before the end of the first year concerned. It consolidates corporate income tax (CIT) and municipal business tax (MBT), but not net wealth tax. This is not a loophole: it is a group cash-flow tool, useful when the costs and the profits sit in different companies.

Many Luxembourg groups pay tax on a profitable subsidiary while carrying losses or financing costs in another company of the same group, without ever letting the two meet. Fiscal unity exists for exactly that: to treat the group as a single taxable base for the space of a financial year. Here is what the regime covers, who really benefits from it, its precise conditions and the limits an honest firm will flag before selling it to you.

What is fiscal unity?

Fiscal unity is an optional regime that lets a parent company and its subsidiaries held at least 95% consolidate their tax results. In practice, the consolidating company adds its own result to that of each integrated company, and tax is then worked out on that combined result, at the parent's level. The profits of some absorb the losses of others within the same year.

One point of vocabulary, because it heads off a costly confusion: fiscal unity is a tax consolidation, not an accounting one. Each company in the group still keeps its own books, draws up its annual accounts and files them with the trade register. The balance sheets are not merged; only the taxable results are added together to calculate the tax. The regime sits in article 164bis of the amended law of 4 December 1967 on income tax, and is detailed in circular L.I.R. No 164bis/1 from the direct tax administration.

The conditions to meet

The regime is not automatic: several conditions must be met, and you have to apply for it. Here they are, as the law stands in October 2026.

Two nuances are worth knowing. The 95% threshold may, exceptionally, be lowered to 75% on the opinion of the Minister of Finance, where the shareholding serves significant economic development, but that is a rare case. And the regime allows horizontal integration between sister companies, where their common parent is a capital company resident in another European Economic Area state and subject to a comparable tax. In other words, you can consolidate subsidiaries held by the same European head of group without integrating that head itself.

Which taxes are covered?

This is the most commonly misunderstood point. Fiscal unity consolidates CIT (corporate income tax) and MBT (municipal business tax), which always go together. It does not consolidate net wealth tax: each company in the group is still taxed separately on its net assets, and each keeps its own minimum net wealth tax. The calculation of all three taxes is set out in our article on corporate tax in Luxembourg.

The practical consequence: consolidation acts on the group's tax on profits, not on its tax on wealth. A group expecting the regime to cut its net wealth tax is pulling the wrong lever. The gain is on CIT and MBT, and only there.

What is it actually for?

The benefit comes down to one sentence: a loss in one group company wipes out a profit in another, in the same year, instead of waiting for hypothetical future years. Take the most common case in Luxembourg. A holding has borrowed to buy an operating company; it carries interest costs and runs a loss. The operating company is profitable and pays the tax. Without consolidation, the holding piles up carried-forward losses it cannot use, while the subsidiary pays full whack. With consolidation, the two offset: the group's tax falls on the profit net of the financing costs.

The effect is first and foremost a cash-flow one: the group only pays tax on its consolidated result, instead of advancing a subsidiary's tax while another's losses sit in a distant carry-forward. For a group in an investment or acquisition phase, the gap adds up quickly. This is exactly the kind of trade-off we work through with a group's directors, as we do for keeping a holding company's books.

The limits and the traps

A serious firm sells the regime with its small print, not just its headline. Here is what to look at before you sign.

• Prior losses stay ring-fenced. Losses a company built up before joining the integrated group stay its own: they are not shared and can only be set against its own future profits, under conditions. Consolidation acts on the period's results, not on the past.
• Each company keeps its obligations. Consolidation removes no filing: each company files its own return, and the consolidating company files the group return on top. That is extra reconciliation work, not an administrative shortcut.
• The consolidating company carries the tax and the advances. It is the one that pays the group's tax and bears the quarterly advances calculated on the consolidated result. Cash centralises at its level, which calls for clear governance between the companies.
• The 5-year commitment is firm. Leaving early is not neutral and can call into question the saving made. The regime is decided for a cycle, not for a one-off opportunistic year.
• Financial years must be aligned. Different closing dates across the group must be harmonised first, which sometimes means a transitional year.

Nothing deal-breaking, but nothing trivial either. Fiscal unity is a good tool when the structure fits and the maths work out. Applied to a group whose companies are all profitable, it adds management complexity with no tax gain.

Who fiscal unity does not help

Let us be straight. If your group is made up of companies that are all profitable, there are no losses to offset, and the regime adds work for nothing. If you have a single company, the question does not arise. And if your shareholdings sit around 80 or 90% without reaching 95%, you are not eligible for the ordinary regime, barring a rare ministerial derogation. Consolidation is made for a real group, widely held, where the members' results diverge. Outside that case, a plain company-by-company loss carry-forward is often enough.

The Advena difference: the group kept in one tool

Fiscal unity is only worth it if each company's results are correct and available in time. Yet a group often splits its accounting across several providers, and no one sees the consolidated result before the year-end. Our approach is the opposite: we keep the holding and its subsidiaries in the same Odoo, set up for Luxembourg, which lets us follow intra-group flows and read the overall position continuously. Multi-company management in Odoo keeps the books cleanly separate while giving the group view, which is exactly what you need to decide on consolidation from figures rather than a hunch. This pairing of the tool with the bookkeeping is at the heart of our approach as a firm for an SME.

One point of principle to close. Fiscal unity is a decision that commits five years and depends on each structure. We inform here on how the regime works; whether it suits you and how to set it up is studied on your own file, and we point you to specialised advice where your group's complexity warrants it. We claim no regulated title we do not hold.

Frequently asked questions

What shareholding is needed for fiscal unity?

At least 95% of each integrated subsidiary's capital, held directly or indirectly and without interruption from the start of the year. A reduction to 75% is possible on an exceptional basis, on the opinion of the Minister of Finance.

Which taxes does fiscal unity consolidate?

Corporate income tax (CIT) and municipal business tax (MBT), always together. Net wealth tax is not consolidated: each company is still taxed separately on its net assets.

How long is the commitment?

At least five financial years, with tacit renewal thereafter. Leaving before the end of the period can call into question the advantage obtained, which makes it a decision for a cycle.

How do you apply for the regime?

Through a joint written application by the companies concerned, sent to the tax office of the consolidating company before the end of the first financial year of the target period. A late application only takes effect the following year.

Can you consolidate sister companies without their parent?

Yes, this is horizontal integration: subsidiaries held by the same parent resident in another European Economic Area state, subject to a comparable tax, can be consolidated between themselves without integrating the parent.

Read on

• Corporate tax in Luxembourg: CIT, municipal business tax and net wealth tax
• Holding company accounting in Luxembourg: what a SOPARFI really keeps
• Setting up a holding in Luxembourg: the SOPARFI explained
• Odoo multi-company: running a holding and its subsidiaries in one database
• What an accounting firm costs in Luxembourg: fixed fee, hourly rates and hidden extras

Why Advena?

• The group view, continuously: holding and subsidiaries in one Odoo, to decide on consolidation from up-to-date results, not an estimate.
• We inform, we do not oversell: we tell you when the regime is worth it and when it only adds needless complexity.
• Clear fixed fee, from €325 per month: the bookkeeping of a simple holding and its subsidiaries, with no hourly billing.
• Honest signposting: for complex multi-jurisdiction structures, we refer you to specialised advice rather than half-serve you.