You own a flat in Paris, Nice or the Dordogne, you live in London, Manchester or Edinburgh, and the idea seems obvious: let the place furnished while you are not there and let holidaymakers pay for its upkeep. Since Brexit, that simple plan sits at the crossing of three French control systems that have all grown stricter. The town hall (mairie) treats short holiday lets as a change of use (changement d’usage) that needs prior authorisation in large towns. The tax office applies a reformed furnished-rental regime that, since the law of 19 November 2024, pushes most unclassified holiday lets into the standard profit regime above only 15,000 euros of annual receipts. And France, as the country where the property stands, taxes the rental income first under the France-United Kingdom double tax treaty, with the United Kingdom giving relief at home. British owners who list first and ask questions later therefore face the same trio of shocks: a municipal fine of up to 100,000 euros, a tax bill computed without the generous flat-rate allowance they expected, and social levies on top. This guide explains, for a British reader and in plain English, every French term as it appears, what permission you need before the first guest arrives, how the current tax figures work on real numbers, and by which routes you can challenge a refusal, a fine or a tax reassessment.

I. Do British owners need permission to let their French flat to holidaymakers?

Yes, in most cases of real interest. The short answer surprises many British buyers because nothing equivalent exists in England: in the larger French communes, turning a home into a repeatedly let holiday flat is not a mere use of your property but a legal change of its authorised use, and that change requires the town hall to agree before you start. The rule applies to French and British owners alike, so Brexit changes nothing here, but British second-home owners are hit hardest in practice because their flats are empty much of the year, their lets are almost always short stays for passing guests, and Paris, the number one British-owned market, enforces the system most actively. Two layers stack on top of each other: the change-of-use authorisation (autorisation de changement d’usage) and the declaration of the furnished tourist accommodation (meublé de tourisme, meaning a furnished flat offered to passing guests for short stays) with its registration number. Confusing the two is the single most common and most expensive mistake, and the Court of Cassation (Cour de cassation, France’s highest civil court) has said so in black and white.

A. When does a furnished holiday let become a change of use needing mairie authorisation?

The legal trigger is set by article L. 631-7 of the Construction and Housing Code (code de la construction et de l’habitation), the statute that governs changes of use of residential premises, read together with the official code text on Légifrance. The Court of Cassation restates the test in these exact terms in its judgment of 27 June 2024 (appeal 23-13.131): “dans certaines communes, le changement d’usage des locaux destinés à l’habitation est soumis à autorisation préalable. Le fait de louer un local meublé destiné à l’habitation de manière répétée pour de courtes durées à une clientèle de passage qui n’y élit pas domicile constitue un changement d’usage au sens de ce texte.” In English: in certain communes, changing the use of residential premises needs prior authorisation, and repeatedly letting a furnished home for short periods to passing guests who do not live there counts as such a change of use. The case papers put the population threshold plainly: in towns of more than 200,000 inhabitants, that pattern of letting is a change of use needing prior authorisation.

The decision that every British owner should know is the judgment of the Third Civil Chamber of 27 June 2024, appeal number 23-13.131, reported on Court of Cassation (case 23-13.131). A commune near Bordeaux sued a tenant and her management company who had repeatedly let a flat for short stays to passing guests. The Bordeaux appeal court had sided with the lettings side because the flat held an official classification as a meublé de tourisme, granted after an inspection visit, which the judges treated as a blanket permission. The Court of Cassation quashed that reasoning with a sentence worth memorising: “une décision de classement en meublé de tourisme ne peut se substituer à l’autorisation de changement d’usage prévue à l’article L. 631-7 du code de la construction et de l’habitation” — a classification decision for a furnished tourist accommodation can never stand in for the change-of-use authorisation. Classification describes the quality of the accommodation; authorisation protects the local housing stock. You need both where the commune requires authorisation, and the classification alone saves nothing.

In Paris and the inner Île-de-France communes, this is not theory. Paris applies the authorisation system and attaches conditions, and the official English-language guidance on the public service portal states the starting point without ambiguity: owners must apply to the town hall for a change-of-use authorisation when converting housing into furnished tourist accommodation. The same official page warns that skipping that step risks a fine of up to 100,000 euros, an order restoring the dwelling to residential use and a daily penalty of 1,000 euros per day per square metre. Those figures come straight from article L. 651-2 of the same code, in force since 21 November 2024 after amendment by Law number 2024-1039 of 19 November 2024, punishes anyone who breaches the change-of-use rules or the conditions attached to an authorisation with a civil fine (amende civile, a court-ordered financial penalty) of up to 100,000 euros per unlawfully converted unit. The same article organises the return-to-housing order: the president of the judicial court (tribunal judiciaire) orders the unit back to residential use within a deadline he sets, then imposes a daily penalty (astreinte) of up to 1,000 euros per day per square metre of converted space. Proceedings run under the fast-track procedure on the merits (procédure accélérée au fond) at the request of the commune, and the fine goes to the commune, so town halls have every incentive to sue. A British owner who lets a Paris studio for thirty weekends a year without authorisation is therefore not risking a warning letter but a court summons, and ignorance of French law is no defence.

Practical consequences follow. Before listing anywhere, ask the mairie of the commune where the flat stands whether a change-of-use authorisation is required for your exact address and your exact letting pattern, and get the answer in writing. Occasional letting of your own second home for a few weeks a year may fall outside the repeated-short-stay pattern in some communes, but only the local rules and the local interpretation decide that, and Paris reads them strictly. If authorisation is needed, apply first and wait for it; conditions, compensation duties or quotas differ from commune to commune and change over time, so never rely on what a neighbour obtained five years ago or on advice written for another town. Keep every receipt, decision and reference number, because the town hall, not you, will reconstruct the letting history from platform data if there is ever a dispute.

B. How do you declare a meublé de tourisme and obtain the registration number?

Once the change-of-use question is settled, the second layer begins: declaring the furnished tourist accommodation itself to the mairie. This declaration (déclaration en mairie) is a separate formality with its own number and its own fine, and it applies whether or not your commune requires the heavier authorisation. In the larger communes the declaration takes the reinforced form, the declaration with registration (déclaration avec enregistrement), a two-step process: first the change-of-use authorisation, then the declaration proper. In smaller communes a simple declaration suffices. Either way the end product is the same: the town hall issues an acknowledgement of receipt carrying the flat’s registration number, and that number must appear on every listing. Once the declaration is lodged, the town hall immediately issues an acknowledgement of receipt carrying the flat registration number. That registration number is standardised nationwide: thirteen characters in three groups encoding the commune, a serial and a check sequence. Platforms are required to display it, and a listing without a valid number in a commune that requires registration is itself evidence of irregularity.

The forgotten-declaration fine is smaller than the change-of-use fine but still painful. The same official page states that skipping the declaration exposes the owner to a civil fine of up to 5,000 euros. Five thousand euros for paperwork sounds disproportionate until you remember the policy behind it: without registration numbers, communes cannot count tourist flats, enforce night caps or cross-check tax returns. For a British owner managing from abroad through a local agent (conciergerie) or management company, the practical lesson is to put the declaration duty expressly in the management contract, in writing, with a named person responsible for filing and for displaying the number, and to demand a copy of the acknowledgement. Agents who list first and declare later expose the owner, because liability follows the owner of the walls, and fines attach per unit, not per person at fault.

Classification (classement) is the optional third layer that many owners confuse with the first two. Classification grades the accommodation from one to five stars after an inspection visit by an accredited body, under article L. 324-1 of the Tourism Code, described on the official business-guidance page on tourist flats. The tax administration explains the vocabulary plainly: where the flat has not obtained that classification, it is an unclassified tourist flat. Classification used to be mainly about marketing and stars; since the 2024 reform it has become a tax dividing line, as the second part of this guide explains, because classified and unclassified flats no longer share the same thresholds or allowances. The Court of Cassation’s warning therefore now carries a double meaning: classification neither replaces the town-hall authorisation, as the 2024 judgment holds, nor, on its own, regularises anything vis-à-vis the commune. Check the classification only after the authorisation and the declaration are secured, and treat anyone who sells classification as a shortcut to legality with scepticism.

For Paris and Île-de-France specifically, British owners should add three local reflexes to the national checklist. First, verify the exact Paris rules for your arrondissement before signing any management mandate, because Paris couples authorisation with conditions that evolve and that your agent must track yearly. Second, remember that most inner-suburb communes now run the registration system too, so a flat in Boulogne-Billancourt, Saint-Denis or Montreuil needs its thirteen-character number just as a Paris flat does. Third, keep the paper trail in France, not only in a London inbox: the acknowledgement of receipt, the authorisation decision and the classification certificate should sit together in one file, available within days if the mairie or the court asks. Owners who can produce that file at the first letter usually negotiate; owners who cannot, litigate.

II. How is a British owner’s French furnished-rental income taxed and charged after Brexit?

Once the flat is let lawfully, the money must be declared correctly on both sides of the Channel, and the order of operations matters. Under the France-United Kingdom double tax convention signed in 2008 and in force, France as the country where the building stands taxes the rents first. Article 6 of the convention, as published by the British government on GOV.UK, the 2008 UK-France double taxation convention, gives the country where immovable property stands the right to tax income from it, and states expressly that this covers income from direct use, letting or any other form of use. The United Kingdom then gives relief against double taxation through its own foreign-tax-credit mechanics, so the same rent is not taxed twice in full, but the French calculation comes first and frames everything. British owners who assume their French rents are already dealt with by their British self-assessment have the treaty backwards: the French return is the primary one. Readers facing the mirror situation, British residents letting out property in England while living in France, will find that reverse mechanics explained in our companion guide on British landlords in France declaring United Kingdom rental income, forms 2047 and 2042, double-tax relief and social charges.

Two preliminary classifications shape the whole French bill. First, furnished letting is taxed as industrial and commercial profits (bénéfices industriels et commerciaux, universally shortened to BIC), not as land income (revenus fonciers), which is the category for unfurnished lets. That single distinction decides the forms, the allowances and the case law. Second, Brexit did not move the taxing right: whether the owner lives in London and files as a non-resident, or lives in France under a Withdrawal Agreement card and files as a resident, French-source furnished rents remain French-taxable income. Residence changes the return in which they are declared and the reliefs around them, never the principle. With those two points fixed, the two live questions are which profit regime applies after the 2024 reform, and what the treaty plus the social levies (prélèvements sociaux, the earmarked social charges added to income tax) add to or subtract from the bill, including how to fight each element.

A. Micro-BIC or régime réel: which tax regime applies after the 2024 reform?

The reform engine is Law number 2024-1039 of 19 November 2024, the statute aimed at regulating tourist flats and rebalancing them with long-term housing. On the tax side it rewrote the thresholds of the micro-enterprise profit regime, and the French tax administration confirms the timetable in its official question-and-answer page: from the 2026 return covering 2025 income, the taxation rules for tourist-flat turnover change. In plain terms, income received in 2025 and declared in spring 2026 is the first vintage fully under the new map. Owners still reasoning with the old 77,700-euro reflex for every flat are therefore already out of date.

The current law is article 50-0 of the General Tax Code (code général des impôts), the micro-BIC statute, in its version in force since 1 July 2026, as explained in the official tax guidance on furnished-rental income and the official tax-office question-and-answer on the new tourist-flat regime. Its new architecture splits furnished tourism into its own lane capped at 15,000 euros for businesses whose main activity is letting tourist flats within the meaning of the Tourism Code, apart from the rural and classified exceptions the statute cross-refers to, alongside a general lane of 83,600 euros for other businesses. The allowance mechanics follow the same split: taxable profit equals turnover excluding tax, minus a flat-rate cost allowance (abattement forfaitaire) of 71, 50 or 30 per cent depending on the lane, with a 305-euro floor. For the tourist-flat lane that matters here, the allowance is 30 per cent.

The administration’s guidance translates that statute into filing reality. For unclassified tourist flats, the official guidance states that the micro-BIC scheme applies where annual revenue collected in 2025 does not exceed 15,000 euros. Crossing that line in a first or second year keeps the scheme for one additional year, with taxable profit equal to revenue minus a 30 per cent flat-rate allowance and no deduction of actual charges. For classified tourist accommodation and guest rooms the ceiling stays far higher: the micro-BIC scheme applies where annual revenue collected in 2025 does not exceed 77,700 euros. Above those ceilings, or voluntarily, the standard profit regime (régime réel, the actual-profit regime where real costs are deducted) takes over: the official guidance summarises the choice: depending on rental income, either the micro-BIC plan with its flat-rate allowance or the actual-profit regime by operation of law, which allows deduction of real expenses and charges. Micro filers must report the gross amount of their income on the online return or on complementary form 2042 C-PRO.

Two short worked illustrations show why the lane matters more than the headline rent. Take a British owner with an unclassified Paris studio grossing 12,000 euros in 2025: inside micro-BIC, the 30 per cent allowance leaves 8,400 euros of taxable profit, and no charge may be deducted on top. Take the same studio, now classified, grossing 24,000 euros: inside micro-BIC at the 50 per cent allowance for that lane, taxable profit is 12,000 euros. Now take an unclassified flat grossing 22,000 euros: micro-BIC is gone, so the file moves to the actual-profit regime, where deductible items typically include management fees, insurance, repair costs within the legal limits, interest on the acquisition loan, the taxe foncière (the French local property tax paid yearly by owners) and accounting depreciation of the furniture and fittings, but the return is heavier and every figure must be evidenced. The statute allows opting into the actual-profit regime even below the thresholds, with the option running yearly and renewing silently, which suits owners with high charges relative to rents. Conversely, owners with almost no charges who overshoot 15,000 euros on an unclassified flat lose twice: no micro allowance worthy of the name, and real costs too thin to beat it. That cliff is the direct product of the 2024 reform, and it is where most British surprise bills now originate.

Record-keeping is not optional colour but a regime condition. Businesses under article 50-0 that have not opted for the actual-profit regime must keep and produce on demand a day-by-day takings journal with invoices and supporting documents. Under the actual-profit regime the obligations are fuller: proper accounts, depreciation schedules and Kilometers of receipts that the inspector will actually read during an audit (contrôle fiscal). British owners running the flat from London should therefore impose one discipline on their agent: monthly statements that reconcile platform payouts, tourist tax (taxe de séjour, the per-person nightly levy collected for the commune) collected and remitted, and costs paid locally, feeding one annual pack the French accountant can file. Returns that cannot be reconciled to platform data are the files that draw the proposal of rectification (proposition de rectification, the formal notice by which the administration states the adjustments it intends to apply), and rectifications unanswered become assessments.

B. France-United Kingdom treaty, social levies and how to challenge a refusal or a bill

The treaty layer starts from the two Article 6 sentences quoted above and works downwards. Because the French flat is immovable property in France, France may tax the letting income, whether the owner is British-resident or French-resident, and the treaty so provides for direct use, letting and every other form of use. The United Kingdom then relieves the double charge under its own rules when the owner is British-resident, which is why the French computation must be right first: every euro of overstated French profit becomes an euro of foreign tax for which full home-country credit may not be available, depending on the British position. Owners should therefore keep the French and British files mirror-consistent — same gross rents, same period, exchange rate documented — and attach the French assessment to the British return file. Where the two administrations characterise an item differently, for example a non-refundable deposit or a cancellation fee, the treaty tie-breakers and the mutual-agreement machinery exist, but they move slowly, so characterisation should be settled at filing time with advice, not discovered at audit time.

Social levies are the second surcharge owners discover late. French rental profits can attract the prélèvements sociaux in addition to income tax, and the applicable fate depends heavily on the owner’s social-security affiliation: owners insured in France, owners covered by a British position with an S1 healthcare certificate, and owners outside any European coordination each sit in different boxes, with case law still moving at the edges. The direction of travel in the courts is best grasped through the Court of Cassation’s social-security chamber, which polices double financing of the French schemes. In its judgment of 25 September 2025, appeal number 22-24.634, published as Court of Cassation (case 22-24.634), the court examined provisions under which French residents working in Switzerland pay both health contributions and social levies on their capital income, recalling that the European coordination regulations “consacrent le principe d’unicité de la législation de sécurité sociale, selon lequel la personne à laquelle les règlements s’appliquent n’est soumise qu’à la législation d’un seul État membre, en sorte que celle-ci, affiliée à un régime de sécurité sociale d’un État membre, ne doit pas contribuer au régime de sécurité sociale d’un autre État membre (CJUE, arrêt du 26 février 2015, De Ruyter, C-623-13, point 35)” — that the regulations enshrine a single applicable social-security legislation, so a person insured in one Member State must not contribute to another Member State scheme, citing the De Ruyter judgment of the Court of Justice of the European Union — before testing the French design against that principle and proportionality. The fact pattern is Swiss, not British, and no sentence of that judgment decides a British owner’s file by itself, but the method is exactly the one a British challenge would borrow: identify precisely which French scheme each euro of levy finances, prove the owner’s affiliation position with certificates rather than assertions, and argue scheme by scheme instead of globally. Owners who simply stop paying levies because Brexit moved their social-security cover back to the United Kingdom invite penalties; owners who file, pay under reservation where appropriate, and evidence their affiliation preserve every route of challenge.

Challenging breaks into three tracks, and each has its own court, its own clock and its own proof. Track one is the town hall: a refused or conditioned change-of-use authorisation, or a disputed registration, goes to the administrative court (tribunal administratif) of the place of the flat. The refusal must state its reasons, and the challenge must answer those reasons one by one with documents — habitability evidence, letting calendars showing the true pattern, comparable authorisations on the same street — rather than with general complaints about housing policy. Deadlines in administrative litigation are short and strict, so the refusal letter should go to a lawyer the week it arrives, not the month after, and any interim letting while the case runs should assume the worst outcome, because letting in defiance of a refusal multiplies the eventual fine base. Track two is the municipal fine itself: article L. 651-2 sends the case to the president of the judicial court in fast-track proceedings, where the commune must prove the repeated short-stay pattern and the owner can contest the facts, the measurements and the proportionality of what is sought. The Bordeaux saga behind the 2024 Court of Cassation ruling shows which defences fail — classification certificates, agency contracts presented as shields, arguments that guests might have stayed longer — and which posture helps: a complete letting history, an authorisation file already lodged, and cessation of the disputed pattern once proceedings start.

Track three is the tax bill: a wrong allowance lane, a disallowed charge under the actual-profit regime, a social-levy item wrongly applied, or a plain double count. The discipline here is paper before pleading. Answer any proposal of rectification within its stated deadline with point-by-point evidence: the classification certificate or its absence fixing the lane, the 2042 C-PRO extract fixing the declared base, the journal and invoices fixing the costs, the S1 or affiliation certificate fixing the levy position, and the treaty article fixing the taxing right. Most British files are won or lost at this administrative stage, long before any court, because inspectors drop adjustments that are properly evidenced and maintain the rest. Where the assessment becomes final and remains wrong, the claim for relief (réclamation) and then the tax courts take over, with the same exhibits plus the assessment itself. Across all three tracks one habit decides outcomes: never let a deadline pass to wait and see, because French procedure rewards the party that files early with reasons and punishes the party that explains late why it filed nothing.

Conclusion

A British second-home owner can lawfully let a French flat furnished and keep a healthy margin, but only in the right order: town-hall authorisation first where the commune requires it, declaration and thirteen-character registration number second, classification third, and only then the listing. Since the 2024 reform the tax lane follows the flat’s status: unclassified tourist flats hit the actual-profit regime above 15,000 euros of annual receipts with a 30 per cent micro allowance below it, while classified accommodation keeps the higher ceiling with a 50 per cent allowance, and France taxes first under Article 6 of the 2008 treaty with home-country relief behind it. The two court decisions that frame the field say the rest: a classification certificate never replaces the change-of-use authorisation, and every euro of social levy must be tied to the scheme it actually finances. Owners who file early, evidence everything and challenge refusals and reassessments through the correct court within its deadline convert most of these risks into routine administration; owners who list first and regularise later convert the same risks into fines, daily penalties and reassessments that no treaty credit can fully cure.