Selling a Luxembourg property is rarely just about price. For any property that isn't your principal residence — a second home, an inherited apartment, a rental investment, a holiday cabin in the Ardennes — the plus-value immobilière (capital gains tax) sits between the gross sale price and the cash you actually pocket.
Many sellers discover this only at the notary appointment, when the figures are no longer negotiable. This walkthrough explains the entire calculation, the deductions, the timing tricks that are legal, and the ones that aren't.
When the plus-value applies
Three exemptions cover most private sellers and should always be checked first:
- Principal residence exemption. If the property has been your main home (résidence principale) for the entire ownership period, the gain is fully exempt. Documentation matters: the address must match your tax residence, your carte d'identité, and your utility bills.
- Inheritance within five years. If you sell inherited property within five years of the death and have not used it as a principal residence, special rules apply that often reduce or eliminate the tax.
- Long holding period. Properties held for more than two years benefit from the demi-taux (half-rate) treatment.
If none of these apply, the gain is fully taxable.
How the gain is calculated
The taxable gain is the sale price minus the indexed acquisition cost. Each component has detail.
Sale price
The gross price stated in the acte de vente, less the directly attributable selling costs: notarial fees on the sale (typically 1–1.5%), agent commission if any, energy certificate cost, mortgage discharge fees, and small administrative expenses. These are deducted from the gross price to give the net realised price.
Acquisition cost (cost basis)
The original purchase price, plus the original purchase costs: notarial fees and registration duties at acquisition (typically 7% in Luxembourg), agent fees if paid by the buyer, and any structural improvement works completed during ownership.
The improvement category is where many sellers under-claim. Eligible works include: extensions, attic conversions, replacement of heating systems, exterior insulation, replacement of windows and roofs, and significant landscaping. Routine maintenance is not eligible — repainting, boiler servicing, broken-tile repairs all fall into ordinary upkeep.
The crucial step: indexation
The acquisition cost is then indexed to the sale year using the official Luxembourg coefficients de réévaluation. Published annually by the Administration des Contributions Directes, these coefficients adjust historical purchase prices for inflation. A property bought in 1995 for €200,000 has, after indexation to 2026, an indexed cost basis of roughly €310,000.
Indexation alone often reduces the taxable gain by 20–40%. Forgetting to apply it is the single most common error in self-prepared declarations.
The half-rate (demi-taux) treatment
For properties held more than two years, the gain qualifies as long-term and is taxed at the demi-taux global — half the seller's marginal income tax rate. For most working-age Luxembourg residents this means an effective rate of around 20% rather than the headline 40%, applied to the calculated gain.
For properties held less than two years, the gain is taxed as ordinary income at the full marginal rate. Timing the sale to cross the two-year threshold can therefore produce significant tax savings.
The €50,000 abattement
A specific allowance of €50,000 (€100,000 for a married couple filing jointly) is available once every ten years to reduce the taxable gain on a long-term real estate sale. This is on top of indexation and the demi-taux. For a couple selling a long-held property, the combination of indexation + abattement + demi-taux typically reduces the headline 40% rate to an effective rate of 12–15%.
A worked example
Consider a couple selling an investment apartment in Belair, bought in 2008 and sold in 2026.
| Item | Amount | |---|---| | Sale price | €1,200,000 | | Selling costs | -€36,000 | | Net realised price | €1,164,000 | | Original purchase price (2008) | €620,000 | | Original purchase costs (notary 7%) | €43,400 | | Improvements (kitchen, bathroom) | €38,000 | | Nominal acquisition cost | €701,400 | | Indexation 2008→2026 (×1.41) | | | Indexed cost basis | €988,974 | | Gross gain | €175,026 | | €100,000 abattement (couple) | -€100,000 | | Taxable gain | €75,026 | | Demi-taux at 21% effective | | | Plus-value tax payable | ~€15,755 |
A back-of-envelope calculation without indexation and abattement would have suggested €498,600 of nominal gain and tax of nearly €100,000 — a stark illustration of why getting the calculation right matters.
Common mistakes
Forgetting indexation entirely. This single error doubles or triples the perceived tax.
Confusing maintenance with improvement. Replacing a worn carpet is maintenance; insulating the entire roof is improvement.
Missing the two-year threshold by days. If you bought on 14 March 2024, do not sell before 15 March 2026, even if a buyer appears earlier.
Using the abattement at the wrong time. Once spent, it is unavailable for ten years.
Treating principal-residence rules sloppily. If you moved out of the property and rented it for the last 18 months before sale, it is no longer a principal residence — even if it was for the previous twenty years.
A dedicated calculator
For a quick first estimate of the plus-value on a specific Luxembourg property, the dedicated tool at plusvalue.lu handles the standard cases — including indexation, demi-taux, and the abattement — and produces a downloadable PDF summary suitable for early planning conversations with your notary or accountant.
For complex cases, or when the property valuation itself needs to be established, a full professional valuation is available via the contact form.