A single building can house a professional office on the ground floor and an apartment on the upper floors. A self-employed person can convert a room in their primary residence into an office. In both cases, the mixed property creates a layering of tax regimes, the mastery of which directly affects the project’s profitability. What concrete differences separate the professional portion from the private portion, and where are the real levers for tax reduction?
Tax breakdown of a mixed property: professional portion versus private portion
The dividing line between professional use and personal use determines everything else. Each tax, each deduction, each exemption is calculated in proportion to this distribution. The table below summarizes the main differences in treatment.
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| Tax criterion | Professional portion | Private portion (residential) |
|---|---|---|
| Declared income | BIC, BNC or rental income depending on the regime | Non-taxable (primary residence) |
| Deduction of expenses (repairs, loan interest) | Deductible pro rata | Not deductible |
| Depreciation of the property | Possible under SCI subject to corporate tax or LMNP regime | Excluded |
| IFI | Excluded from the taxable base if conditions are met | Included in the taxable base |
| Property tax | Due, but recoverable from the tenant in mixed lease | Due by the owner |
| Capital gains on sale | Professional capital gains regime | Exemption for primary residence |
Surface area is the reference criterion for determining the share. When this criterion is not relevant (diffuse activity, shared use of certain rooms), the administration accepts another method of distribution, provided it is justifiable.
Understanding the taxation of a mixed property starts with this breakdown, as an error in the share affects every line of the declaration.
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Bank financing of a mixed property: the often-overlooked HCSF constraint
Before even discussing tax advantages, the feasibility of a mixed property project faces a financial obstacle. The rules of the High Council for Financial Stability strictly regulate the granting of credit since 2023-2024.
The debt ratio is capped at 35% of income. Banks only consider the projected rental income from the professional or rental portion at about 70% in the calculation of borrowing capacity. An owner relying on a monthly rent from the professional portion will therefore see their borrowing capacity calculated based on only a fraction of that amount.
This 30% discount on projected rental income radically changes the sizing of the project. A property that appears to have comfortable rental profitability on paper may become ineligible for credit once the HCSF rule is applied.
Concrete impact on the setup
For a mixed property where the rental portion represents a significant part of the financing, the margin for maneuver is reduced. The owner must either increase their personal contribution or reduce the space dedicated to professional activity to lower the borrowed amount.
This point almost never appears in tax guides, even though it conditions access to the mixed property for the majority of buyers.
Tax regime of the mixed property: SCI subject to corporate tax, LMNP and lesser-known exemptions
The choice of tax regime determines the depth of accessible advantages. Three configurations deserve distinct analysis.
SCI subject to corporate tax: full depreciation but costly exit
Holding a mixed property through an SCI subject to corporate tax allows for the full depreciation of the professional portion of the property. The corporate tax rate applied varies from 15% to 25% depending on the result. During the operating phase, the tax burden remains contained thanks to the deduction of depreciation and expenses.
However, the sale of the property triggers a capital gain calculated on the net book value (after depreciation), which significantly increases the exit tax. The advantage in operation comes at the cost of resale.
LMNP and the Jeanbrun scheme
For the furnished rental portion of a mixed property, the LMNP regime remains a common lever. The 2026 finance law adds a new option: the Jeanbrun scheme, which allows for the depreciation of certain rental properties under the income tax regime. This mechanism directly competes with the SCI subject to corporate tax and may change the balance for owners who do not wish to create a corporate structure.
Exemption for renting part of the primary residence
When an owner rents a room or an annex of their primary residence and the rent remains below a ceiling set each year by the tax administration (article 35 bis of the CGI), the rents received can be completely exempt from tax. This provision applies to both long-term rentals and seasonal furnished rentals under certain conditions.
- The rented accommodation must constitute the tenant’s primary residence (or a seasonal rental in certain cases)
- The annual rent must not exceed the regulatory ceiling updated each year
- The rented room must be an integral part of the owner’s primary residence
This exemption remains underutilized even though it completely eliminates taxation on rental income for the concerned portion.
IFI and mixed property: only the private fraction enters the taxable base
For owners subject to the real estate wealth tax, the mixed property offers a lever for reducing the taxable base. The professional portion can be excluded from the IFI if it is genuinely and exclusively allocated to an eligible activity.
The breakdown relies on the share of actual use. The surface area remains the priority criterion, but another method of distribution may be retained if the configuration of the property justifies it. The declaration must reflect this distribution coherently with other tax declarations (income, property tax).
- A 20 m² office in a 100 m² dwelling excludes 20% of the property’s value from the IFI taxable base
- Shared-use rooms (entrance, hallway) are distributed pro rata
- The burden of proof lies with the owner in case of an audit
The tax gap can be substantial for estates close to the threshold triggering the IFI, where every excluded fraction from the taxable base counts.
The mixed property is not just a single tax advantage but a combination of mechanisms that stack: deduction of professional expenses, depreciation under certain regimes, partial exemption from IFI, and in some cases, total exemption from rents. The actual profitability of the setup depends less on the chosen regime than on the rigor of the breakdown between professional and private use, as it is this distribution that the tax administration verifies as a priority.