You own a flat in Paris, a cottage in the Dordogne or a seaside studio on the Côte d’Azur, and since Brexit you spend only part of the year there. The rest of the time the property sits empty, so letting it by the night or the week on Airbnb or a similar platform looks like the obvious way to cover the taxe d’habitation (the French local residence tax still due on second homes), the maintenance bills and the mortgage. Thousands of British owners have reached exactly that conclusion — and a growing number have then received two unpleasant letters: one from the mairie (the town hall) ordering them to stop and pay a five-figure civil fine, and one from the French tax office reassessing several years of rents with penalties. Both letters rest on rules that changed recently, and both can be challenged — but only if you understand which regime applies to you before you file anything.

This guide explains, for a British owner after Brexit, the two fronts of a lawful short-term let: first, the town-hall front — registration as a meublé de tourisme (furnished tourist accommodation), the declaration number that must appear on every advert, and the changement d’usage (change-of-use) permission your second home needs in large towns and in Paris; second, the tax front — why your rents are taxed as business profits rather than rental income, the choice between the simplified micro-BIC scheme and the régime réel (actual-profit regime), the threshold that turns a LMNP (non-professional furnished landlord) into a LMP (professional furnished landlord), the social charges on top of income tax, and how the France–UK double tax treaty divides the bill between Paris and HMRC. It closes with the practical remedies: how to declare in both countries, and how to contest a fine, a refusal or a reassessment.

I. Can you lawfully let your French second home to short-stay guests after Brexit?

Yes — being British changes nothing about the letting rules themselves. Since the end of the transition period you are a third-country national for residence purposes, which matters for how many days you may stay, but the rules on short-term letting apply to every owner regardless of nationality. They come in two layers that many British owners confuse: registration, which applies almost everywhere, and change-of-use permission, which applies in the towns that voted for it — including Paris, most of the inner Paris region, and the large tourist cities. Missing either layer is punished separately, so take them in order.

A. How do you register a meublé de tourisme and obtain the declaration number?

French law gives short-term furnished letting its own legal category. Under Article L. 324-1-1 of the Tourism Code, “les meublés de tourisme sont des villas, appartements ou studios meublés, à l’usage exclusif du locataire, offerts à la location à une clientèle de passage qui n’y élit pas domicile et qui y effectue un séjour caractérisé par une location à la journée, à la semaine ou au mois”. Every word of that definition matters for a British second-home owner: your flat is offered à l’usage exclusif du locataire (for the guest’s exclusive use, unlike a spare room in your own home), to une clientèle de passage (passing trade — holidaymakers, not tenants), who n’y élit pas domicile (do not make it their home) and stay by the day, week or month. If your arrangement matches that description, you are running a meublé de tourisme whether you use Airbnb, Booking.com, a local agent or your own website, and the registration duty applies to you personally — it cannot be delegated away from the owner.

Registration is a prior online declaration, and it produces the number that must appear on your adverts. The Code states that “Toute personne qui offre à la location un meublé de tourisme procède préalablement en personne à une déclaration soumise à enregistrement auprès d’un téléservice national opéré par l’organisme public unique mentionné au premier alinéa du II de l’article L. 324-2-1” — in plain terms, you file in your own name on the national online portal (téléservice) before the first guest arrives, and “A la réception de la déclaration complète, le téléservice délivre sans délai un avis de réception électronique comprenant un numéro de déclaration.” That numéro de déclaration (declaration number) must be shown on every listing; platforms are now obliged to collect it and towns can order an advert withdrawn when the number is missing or false. The town hall (mairie) of the place where the property sits receives your file automatically and can audit it, so declare the exact address, your identity as owner, and whether the property is your main or second home — a false statement is punished on its own.

The fines for skipping this step are administrative fines imposed by the commune, and they are steep enough to wipe out a season of rents: “Toute personne qui ne se conforme pas aux obligations résultant du III est passible d’une amende administrative prononcée par la commune, dont le montant ne peut excéder 10 000 €.” and “Toute personne qui effectue de fausses déclarations dans le cadre de la déclaration préalable prévue au III ou qui utilise un faux numéro de déclaration est passible d’une amende administrative prononcée par la commune, dont le montant ne peut excéder 20 000 €.” The official service-public.fr guidance for second-home owners describes the same sequence: declare the furnished accommodation first, then apply to the town hall for change-of-use permission where the commune requires it. Note one trap British owners fall into: the famous 120-day ceiling — “Toute personne qui offre à la location un meublé de tourisme qui est déclaré comme sa résidence principale ne peut le faire au-delà de cent vingt jours au cours d’une même année civile, sauf obligation professionnelle, raison de santé ou cas de force majeure.” — applies only to a résidence principale (main home). A second home (résidence secondaire) has no 120-day shelter at all: beyond registration, it needs the change-of-use permission below, for every night let.

B. When does letting a second home require change-of-use permission, and what does Paris demand?

In the communes that adopted the scheme — Paris, the inner-ring towns of the Paris region, cities of over 200,000 inhabitants and parts of the tourist coast — turning a home into short-term tourist accommodation is a changement d’usage (change of use) that needs prior permission from the town hall. The mechanism sits in the Construction and Housing Code: “Dans ces communes, le changement d’usage des locaux à usage d’habitation peut être soumis, sur décision de l’organe délibérant, à autorisation préalable dans les conditions fixées à l’article L. 631-7-1.” Once the municipal council has voted the scheme in, letting your second home by the night without that autorisation préalable (prior permission) is unlawful even if you registered the property correctly — registration and permission are cumulative, and the town can pursue you for each missing piece.

The courts have settled what counts as a change of use, and their answer leaves no room for the usual excuses. In its landmark Paris decision of 18 February 2021, the Third Civil Chamber of the Court of Cassation upheld the city’s action against owners who had let a two-room flat twice, for four and six months, to passing clients without permission (Court of Cassation, Third Civil Chamber, 18 February 2021, appeal no. 19-13.191, ECLI:FR:CCASS:2021:C300198). The Court confirmed that repeated short lets to clients who do not settle there change the use of the premises, rejecting arguments based on the civil nature of the activity or on back-to-back bookings that allegedly housed a single occupant. Two years later it confirmed the same analysis and rejected an owner’s appeal (Court of Cassation, Third Civil Chamber, 15 February 2023, appeal no. 22-10.187, ECLI:FR:CCASS:2023:C300122). Most recently, on 3 September 2026, it quashed a court of appeal that had spared an owner on the grounds that her seasonal letting without hotel services was civil in nature: the Court restated that “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.” (Court of Cassation, Third Civil Chamber, 3 September 2026, appeal no. 25-16.157, ECLI:FR:CCASS:2026:C300463), and held that the lower court had ruled on irrelevant grounds because it had itself found repeated short lets of a residential flat without prior permission. For a British owner, the message is blunt: neither your British tax residence, nor the absence of hotel services, nor letting through a British platform prevents the reclassification.

The sanction is a civil fine ordered by the president of the judicial court (tribunal judiciaire) on application by the commune: “Toute personne qui enfreint les dispositions des articles L. 631-7 ou L. 631-7-1 A ou qui ne se conforme pas aux conditions ou obligations imposées en application des mêmes articles L. 631-7 et L. 631-7-1 A est condamnée à une amende civile dont le montant ne peut excéder 100 000 € par local irrégulièrement transformé.” The service-public.fr guidance for second-home owners gives the same warning in practical terms: letting without the required permission means exposure to the maximum fine, an order to restore the dwelling to residential use, and a daily penalty running until compliance. In Paris specifically, permission is granted only against compensation — you must convert an equivalent non-residential floor area back into housing in the same neighbourhood, a condition no ordinary British second-home owner can meet in practice. That is why Paris-oriented purchases marketed to Britons as “ideal Airbnb investments” so often end in fines: the permission is theoretically available and practically out of reach, and the town’s enforcement unit cross-checks platform adverts against the register. Before buying or letting, ask the mairie in writing whether the address needs permission, keep the written reply, and if permission is refused, demand the stated reasons — an unreasoned refusal is itself open to challenge before the administrative court, as explained in Part II.

II. How is the rental income taxed in France and in Britain?

Here comes the second surprise for British owners: in France, furnished rents are not rental income at all. They are business profits — bénéfices industriels et commerciaux, universally shortened to BIC — with their own declaration forms, their own simplified and actual-profit regimes, and social charges on top of income tax. The France–UK double tax treaty then gives France, where the property stands, the first right to tax, while HMRC taxes you again but must give credit for the French tax. Get the French regime wrong and you pay too much in France and cannot recover the excess in Britain, because HMRC only credits tax properly due. So the French analysis comes first.

A. Micro-BIC or régime réel: which French tax regime fits a British owner’s rents, and when do you turn professional?

The starting point is that any individual who lets furnished residential premises is running a business for income-tax purposes. Article 35 of the General Tax Code (Code général des impôts, the CGI) provides that business profits include those of “5° bis Personnes qui donnent en location directe ou indirecte des locaux d’habitation meublés” — persons who let furnished residential premises directly or indirectly. That single line reclassifies your Airbnb rents: you are not a passive landlord receiving revenus fonciers (unfurnished rental income) but the operator of a furnished-letting business, even with one flat and even if you live in London. The consequences follow mechanically: business-loss relief rules, business social charges, registration of the business with the company formalities service, and the choice between the simplified and actual-profit methods of computing the profit.

Most small British owners fall by default into the micro-BIC scheme — a flat-rate allowance in place of deducting real costs — but since the so-called Le Meur Act of 19 November 2024 the allowance for ordinary tourist lets has shrunk dramatically. Article 50-0 of the CGI now sets three turnover ceilings: standard sales and lodging businesses up to 203,100 euros, other businesses up to 83,600 euros, and crucially “1° bis 15 000 € s’il s’agit d’entreprises dont l’activité principale est de louer directement ou indirectement des meublés de tourisme, au sens du I de l’article L. 324-1-1 du code du tourisme”. Below 15,000 euros of annual rents from an unclassified tourist let, you stay in micro-BIC with “un abattement de 30 % pour le chiffre d’affaires provenant d’activités de la catégorie mentionnée au 1° bis” — a 30 per cent allowance, so 70 per cent of the rents is taxable and no charge may be deducted. Classified lets (meublés classés, officially star-rated) and rural guest rooms keep more generous allowances, which is why having an accredited body rate your property can be worth real money. Above the ceiling, or by election (option) made with your return, you move to the régime réel: you deduct the true costs — agency commission, platform fees, insurance, repairs, taxe foncière (the French property ownership tax), loan interest and depreciation of the furniture and, in some structures, of the building — and you can carry forward a genuine business loss. As a rule of thumb, owners with heavy costs (mortgage interest, major works, large commissions) usually gain by electing for the actual-profit regime despite the bookkeeping, while owners of a studio owned outright with few costs do better staying in micro-BIC; run both computations before the filing deadline, because the election binds you for a year renewable by tacit agreement.

The second tax boundary is the one between the LMNP — loueur en meublé non professionnel, the non-professional furnished landlord — and the LMP — loueur en meublé professionnel, the professional. Article 155 of the CGI provides that “L’activité de location directe ou indirecte de locaux d’habitation meublés ou destinés à être loués meublés est exercée à titre professionnel lorsque les deux conditions suivantes sont réunies”, namely that “Les recettes annuelles retirées de cette activité par l’ensemble des membres du foyer fiscal excèdent 23 000 €” — annual receipts of the whole tax household (foyer fiscal, meaning you plus your spouse or civil partner taxed jointly) exceed 23,000 euros — and that those receipts exceed the household’s other earned income (wages, other business profits, farm profits, professional income). Both tests must be met together. Crossing into LMP status changes the treatment of losses (usable against total income, with conditions), takes the property out of the wealth-tax base in some cases, and brings specific social-security affiliation — so a British couple whose combined French rents pass 23,000 euros should check the second test carefully rather than assume professional status, and document the comparison year by year.

On top of income tax come the prélèvements sociaux — social charges at a combined 17.2 per cent (CSG and CRDS) levied on property and investment income. Article L. 136-6 of the Social Security Code provides that “Les personnes physiques fiscalement domiciliées en France au sens de l’article 4 B du code général des impôts sont assujetties à une contribution sur les revenus du patrimoine assise sur le montant net retenu pour l’établissement de l’impôt sur le revenu”. If you are French tax-resident — and British owners who settled in France full-time usually are, under the worldwide-income rule — the 17.2 per cent applies to the net furnished profit on top of income tax. If you stayed UK-resident and hold only a French holiday home, you still pay French income tax on the French-source rents, computed with a floor: Article 197 A of the CGI provides that for persons without French tax domicile, “l’impôt ne peut, en ce cas, être inférieur à un montant calculé en appliquant un taux de 20 % à la fraction du revenu net imposable inférieure ou égale à la limite supérieure de la deuxième tranche du barème de l’impôt sur le revenu et un taux de 30 % à la fraction supérieure à cette limite” — unless you show that the French tax on your worldwide income would be lower, in which case that lower average rate applies. Non-resident British owners also remain liable for the social charges on French property income at the same overall economic level, collected through a specific levy — so obtain the exact assessment notice (avis d’imposition) calculation and check which rate was applied before paying.

B. How do you declare in both countries, use the treaty and challenge the bill?

The treaty rule is simple and official. The French tax administration’s own commentary on the France–UK treaty explains that the state where the property sits has the prior right to tax (official BOFIP commentary on the France–UK treaty): for your French flat, that state is France. For your French flat, that state is France: France taxes the rents under the BIC rules above, whether you live in London, Paris or Edinburgh. The treaty itself is the double tax convention between France and the United Kingdom signed on 19 June 2008 (published by the French tax administration, treaty text on impots.gouv.fr), and its property article reserves precisely this priority to the state of location. Britain then taxes the same rents if you are UK-resident — HMRC taxes worldwide income — but must relieve the double charge: under HMRC guidance on foreign income, a UK resident usually reports the French rents in a Self Assessment tax return and claims Foreign Tax Credit Relief for the tax already paid in France, where eligible. In practice: file the French return first, pay the French tax, then claim the credit on the UK Self Assessment foreign pages with the French assessment as evidence. Keep both assessments for six years; if the credit is refused because HMRC considers the French tax was not properly due — for example where you deducted nothing under micro-BIC although the régime réel would have cut the French bill — the remedy usually lies in correcting the French return, not in arguing with HMRC.

On the French side, declare the rents on the business-income supplement (form 2042-C-PRO) alongside the main return (form 2042), with foreign-bank details where relevant on form 3916, within the May–June online deadlines — non-residents file at the Noisy-le-Grand foreign-tax office (Service des impôts des particuliers non-résidents). Declare the business itself on creation through the online company formalities portal, which issues the SIRET number the tax office expects. If the town hall fined you, two different judges are involved and owners constantly apply to the wrong one: the civil fine for unauthorised change of use is contested before the judicial courts by attacking the factual basis (was the flat truly residential on 1 January 1970? were the lets truly repeated short lets to passing clients within the Court of Cassation’s definition?), while a tax reassessment is contested by a formal claim (réclamation contentieuse) to the tax office within the statutory deadline, then before the administrative court (tribunal administratif). A refusal of change-of-use permission is likewise challenged before the administrative court within two months, where the strongest arguments are an unreasoned decision, an error in the residential-use finding, or unequal treatment compared with similar granted files on the same street. For Paris and Île-de-France owners specifically: check the Paris règlement municipal compensation requirement before promising anything to a buyer or agent, print the advert with the declaration number visible, reconcile platform payout statements with the declared turnover euro for euro, and never ignore a town-hall questionnaire about letting days — the one-month reply deadline in the Tourism Code runs from receipt, and silence is treated as an admission that feeds the fine.

Conclusion

Letting a French second home by the night after Brexit is lawful, but it is a regulated business, not a casual top-up income. Register the meublé de tourisme before the first guest, display the declaration number, and secure the change-of-use permission wherever your commune requires it — in Paris, verify the compensation rule before you count on any income at all, because the 100,000-euro civil fine per unlawfully converted flat is calibrated to hurt. Treat the rents as what French law says they are, business profits: measure your turnover against the 15,000-euro micro-BIC ceiling with its 30 per cent allowance, compare with the actual-profit regime whenever you carry real costs, watch the 23,000-euro household test that marks the border of professional status, and budget for the 17.2 per cent social charges alongside income tax — or the 20 and 30 per cent minimum rates if you are not French-resident. Then let the treaty do its job: France taxes first as the state of location, and HMRC gives credit on your Self Assessment return against the French assessment. Every adverse decision in this chain — the missing permission, the fine, the reassessment, the refused credit — has its own judge and its own deadline, and the files that win are the documented ones: the town hall’s written reply, the printed advert, the reconciled payout statements, the assessment notices kept on both sides of the Channel. Put that paper trail together before the season starts, and the French second home can pay its way without paying twice.