You moved to France after Brexit, kept the buy-to-let flat in Leeds or the terraced house outside Manchester, and now a buyer has made an offer you want to accept. The conveyancer in England talks about Capital Gains Tax and a 60-day deadline. A friend in France warns that Paris will tax the same sale again. Both are right, and neither bill cancels the other automatically. The tax treaty signed by France and the United Kingdom on 19 June 2008 does not hand the whole gain to one country. It lets the United Kingdom tax the sale first, as the country where the bricks stand, and it lets France tax it second, as the country where you now live, while obliging France to subtract the British tax from its own bill within a strict ceiling. That ceiling, the paperwork and the order in which you pay decide whether you hand over money twice on the same profit or only once. This article walks through the full chain in the order you will meet it: the British charge and its 60-day return, the French charge built on worldwide taxation, the capped credit that prevents double taxation, and the remedies when either administration gets the figures wrong.
I. Why Both Countries Tax the Same Sale, and Why the United Kingdom Moves First
A. Will the United Kingdom tax my property sale even though I live in France?
Yes. The treaty gives the country where the property stands the first right to tax the gain. Article 14, paragraph 1 of the France–United Kingdom convention of 19 June 2008 provides, in the official English text published by the British government, that gains from the disposal of immovable property covered by Article 6 and situated in one of the two countries may be taxed in that country. Your Leeds flat or Manchester house is immovable property situated in the United Kingdom, so the gain on its sale may be taxed there even though you are resident in France. The French tax administration reads the same rule identically: its official commentary states the same rule, under which gains on the disposal of buildings covered by Article 6 are taxable in the country where the buildings stand. The two readings point the same way, and that convergence matters, because each administration will expect you to pay it first.
British tax on the sale is Capital Gains Tax, the national tax on the profit made when an asset is sold for more than it cost. Since 6 April 2020 a special clock applies to residential property: any Capital Gains Tax due on a UK residential property must be reported and paid within 60 days of completion, and the official guidance warns that late reporting and payment attract interest and a penalty. Completion (completion) is the day the sale legally concludes and the price is paid, not the day contracts are exchanged, so count the 60 days from the completion statement your conveyancer sends you. The return is filed through the HMRC online UK property account, which is separate from the yearly Self Assessment return (Self Assessment, the annual British tax return): you report and pay now, then reconcile the figures later in the annual return if you file one.
The British rate on residential property gains depends on your income band. The official rates page explains that gains falling within the basic Income Tax band bear 18% while gains above that band bear 24%, for gains made from 6 April 2026 onwards. Before applying those rates you deduct the annual tax-free allowance (annual exempt amount), which stands at £3,000 for the 2026 to 2027 tax year. In plain terms: take the sale price, subtract the purchase price and allowable costs, subtract £3,000, then apply 18% to the slice that fits inside your remaining basic-rate band and 24% above it. Keep the completion statement, the original purchase deed and every invoice for works, because the British computation starts from documented figures and the French computation will ask for the same papers.
One contrast sharpens the picture. When the direction is reversed, a person who lives in Britain and sells a flat in France faces a French withholding levy (prélèvement) under Article 244 bis A of the French Tax Code (Code général des impôts), which applies, subject to treaties, to gains on French-situated property realised by non-residents. You are in the mirror situation: resident in France, selling British-situated property. No French withholding applies at the London completion, but the French annual machinery described below will catch the same gain, which is why paying the British bill first and keeping every receipt is the foundation of everything that follows.
B. Why does France tax a house that stands in England?
Because France taxes its residents on their worldwide income, including gains on property abroad. Article 4 A of the French Tax Code states: “Les personnes qui ont en France leur domicile fiscal sont passibles de l’impôt sur le revenu en raison de l’ensemble de leurs revenus.” In English: persons whose tax home (domicile fiscal, the tax residence defined by French law) is in France are liable to income tax on all of their income. The second sentence of the same article draws the boundary: “Celles dont le domicile fiscal est situé hors de France sont passibles de cet impôt en raison de leurs seuls revenus de source française”, meaning those whose tax home is outside France are liable only on French-source income. So the entire French claim on your Leeds sale turns on one question: is your domicile fiscal in France at the time of the sale?
Article 4 B, and meeting any one of them is enough. The Paris Administrative Court of Appeal recalled the wording in a 2023 residence dispute: “1. Sont considérées comme ayant leur domicile fiscal en France au sens de l’article 4 A : / a. Les personnes qui ont en France leur foyer ou le lieu de leur séjour principal. b. Celles qui exercent en France une activité salariée ou non, à moins qu’elles ne justifient que cette activité y est exercée à titre accessoire ; (…) c. Celles qui ont en France le centre de leurs intérêts économiques. (…)”. In English: your tax home is in France if your household base (foyer, where you normally live and centre your personal life) or your main place of stay is in France, or if you carry on a professional activity in France otherwise than incidentally, or if the centre of your economic interests is in France. For a British retiree or remote worker settled in the Dordogne or in Paris with the family home there, the first test is usually met on its own, and the treaty tie-breaker only becomes relevant if the United Kingdom still claims you too, a situation examined in our guide to the tie-breaker that decides where you are resident when both countries claim you.
The same court decision, published on 20 October 2023 under number 22PA00816, explains how judges sequence domestic law and treaty: “Si une convention bilatérale conclue en vue d’éviter les doubles impositions peut, en vertu de l’article 55 de la Constitution, conduire à écarter, sur tel ou tel point, la loi fiscale nationale, elle ne peut pas, par elle-même, directement servir de base légale à une décision relative à l’imposition.” In English: a bilateral treaty to avoid double taxation may, under Article 55 of the Constitution, set aside domestic tax law on a given point, but it cannot by itself directly serve as the legal basis for a tax assessment. The practical consequence is a two-step check the judge performs and you should mirror: first, is the French charge validly established under domestic law, meaning Articles 4 A, 4 B and the property-gains rules below; second, does the treaty block that domestic charge. For your sale the answer at step two is that the treaty does not block France, because Article 14 lets the situs country tax without reserving it exclusivity, and Article 24 then organises relief rather than exemption. The court also clarified the household-base test for a single person without family charges: “le foyer d’un contribuable célibataire, sans charge de famille, s’entend du lieu où il habite normalement et a le centre de sa vie personnelle, sans qu’il soit tenu compte des séjours effectués temporairement ailleurs en raison des nécessités de la profession ou de circonstances exceptionnelles”, meaning the foyer is where you normally live and centre your personal life, ignoring temporary stays elsewhere for work or exceptional circumstances. Short trips back to Britain to prepare the flat for sale do not move your foyer back across the Channel.
The scope of the French charge on property gains is set by Article 150 U of the Tax Code, which brings within the French property-gains regime the gains realised by individuals on the sale for consideration of buildings and related rights, subject to the specific regimes for business, farm and professional profits. Your British buy-to-let is not a French business asset, so it lands in this general regime, and the French computation starts from the same economic event the British return already taxed.
II. How France Computes Its Bill, Subtracts the British Tax, and How You Challenge Errors
A. How is the French bill calculated and how does the capped credit work?
France computes its tax under its own rules, then grants a credit for the British tax, capped at the French amount. The starting point is the net gain (plus-value nette imposable, the taxable net gain): the gain is the difference between the sale price and the purchase price, as the official impots.gouv.fr guidance puts it. From that difference, holding-period relief (abattement pour durée de détention, a statutory percentage reduction that grows with years of ownership) may apply before the rates bite. After those reductions, the gain bears income tax at 19% and social levies (prélèvements sociaux, the CSG, CRDS and solidarity charges that fund French social protection) at a combined 17.2%. The 19% rate comes straight from statute: Article 200 B of the Tax Code provides that “Les plus-values réalisées dans les conditions prévues aux articles 150 U à 150 UC sont imposées au taux forfaitaire de 19 %.”, meaning gains realised under Articles 150 U to 150 UC are taxed at the flat rate of 19%. The social levies reach your gain through Article L. 136-6 of the Social Security Code (Code de la sécurité sociale): “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”, with the base expressly including “Des plus-values, gains en capital et profits soumis à l’impôt sur le revenu”, meaning individuals with their tax home in France pay the contribution on capital gains subject to income tax. Because you are French-resident under Article 4 B, the British gain sits inside that base.
The holding-period relief follows a fixed statutory schedule, and its length surprises many British sellers used to shorter British tapers. The official guidance sets a fixed scale: for income tax, relief runs at 6% per year of ownership from year six to year twenty-one, then 4% for the twenty-second year, giving full exemption from income tax after twenty-two years. For the social levies the slope is gentler, at 1.65% per year from year six to year twenty-one, then 1.60% for the twenty-second year and 9% per year beyond, so that full exemption from the social levies arrives after thirty years of ownership. A flat bought in 2011 and sold in 2026, held fifteen years, therefore carries 60% relief against the 19% income-tax base and 16.5% relief against the 17.2% social-levies base, a gap that explains why the social charge often dominates the French bill on mid-length ownerships. Readers who already let the property will recognise the companion problem of how your UK rental income is taxed while you live in France, where the same 17.2% levies apply to rents year after year.
Once the French tax is computed, the treaty organises relief, and its wording is the most important paragraph in this article. Article 24, paragraph 4(b) of the convention allocates the duty to relieve: where gains may be taxed by one country under Article 14, paragraphs 1, 2 or 3, the other country, and not the first, must eliminate the double taxation. Your gain may be taxed by the United Kingdom by reason of Article 14, paragraph 1, so France, the other contracting country, and not the United Kingdom, must eliminate the double taxation. The method for France sits in Article 24, paragraph 3(a)(ii): the French resident is entitled to a credit equal to the tax effectively paid in the United Kingdom on the gain, capped at the French tax attributable to that same gain. French courts call this ceiling the butoir (literally the stop-block): in a 2023 decision on treaty credits, the Paris Administrative Court of Appeal restated that “le bénéficiaire de ces revenus a droit à un crédit d’impôt imputable sur l’impôt français, égal au montant de l’impôt payé ou supporté dans l’Etat d’origine, qui, en vertu de la règle dite […] ne peut toutefois excéder le montant de l’impôt français correspondant à ces revenus”, meaning the recipient is entitled to a credit against French tax equal to the tax paid in the source country, which under the butoir rule cannot exceed the French tax on that income. The tax administration’s own guidance for residents selling foreign buildings says exactly the same in plainer words: a credit against the French tax is available, set by the treaty, equal to the French tax computed on the gain or to the foreign tax without exceeding the French tax.
A worked illustration, using rounded figures and the verified rates, shows how the ceiling bites. Suppose you bought the Leeds flat for £180,000 in 2011 and complete the sale at £300,000 in 2026, a £120,000 gain held fifteen years. On the British side, subtract the £3,000 annual exempt amount, leaving £117,000: if £17,700 of that falls inside your remaining basic-rate band it bears 18%, which is £3,186, and the remaining £99,300 bears 24%, which is £23,832, for a British bill of £27,018 payable within the 60-day window. On the French side, the fifteen-year holding gives 60% relief against income tax, so the 19% rate bites on £48,000, which is £9,120, and 16.5% relief against the social levies, so 17.2% bites on £100,200, which is £17,234, for a French computation of £26,354 before credit. The treaty credit equals the British tax but cannot exceed the French figure, so £26,354 of credit wipes out the French bill and the £664 of excess British tax is simply lost: no refund, no carry-forward. Reverse the holding period to five years with no relief and the French figure would be roughly £43,440, the same £27,018 credit would leave about £16,400 payable in France. The lesson is symmetrical and worth stating bluntly: when British tax exceeds French tax you pay nothing more in France but recover nothing either, and when French tax exceeds British tax you pay the difference to Paris. Either way the two computations must use consistent euro conversions of the sterling prices, and keeping the dated exchange calculation with the file avoids the most common avoidable dispute.
One post-Brexit trap deserves its own paragraph, because it costs sellers the full 17.2% they assumed an S1 healthcare certificate or British National Insurance record would remove. Since the end of the transition period the United Kingdom is a third country outside the European Union, the European Economic Area and Switzerland, and French courts hold that European social-security coordination does not shield third-country affiliates from French levies on capital. In a 2018 decision on social charges over a Paris property gain, where the seller invoked Australian affiliation, the Paris court recalled that “ce règlement ne fait pas obstacle à ce qu’une personne affiliée à la sécurité sociale dans un État tiers à l’Union européenne autre que la Suisse ou les États membres de l’Espace économique européen soit soumise à ces mêmes prélèvements”, meaning the coordination regulation does not prevent a person affiliated to social security in a third country outside the Union, other than Switzerland or the European Economic Area, from being subjected to those same levies. Read the United Kingdom in place of Australia: British National Insurance alone does not exempt your Leeds gain from the French prélèvements sociaux, and any claim to reduced social charges must rest on a documented French-law exemption, not on the fact of paying into the British system. Two related warnings follow from the same logic. First, British reliefs such as private residence relief or letting relief reduce the British bill only; they do not shrink the French base, which is computed under French rules, so a sale fully sheltered in London can still produce a bill in Paris with nothing to credit against it. Second, converting the sterling gain at a favourable rate or deducting costs the French computation does not recognise will be unwound on audit, with the credit recomputed on the corrected French figure.
B. What must I file, when, and how do I challenge a wrong bill?
Three deadlines govern the sale, and they run on different clocks in different countries, so diary them on completion day. In Britain, the 60-day online return and payment described above comes first, with interest and penalties for lateness. In France, the administration requires its own property-gain return within the month after the sale: where you have realised a gain outside mainland France and the overseas departments and that gain is not exempt from French tax under a treaty, you must file within the month following the disposal, with your tax office, return 2048-IMM for a building or 2048-M for shares in a property-rich company. In English: if you realised a gain outside mainland France and the overseas departments and that gain is not exempt from French tax under a treaty, you must file within the month following the disposal, with your tax office, return 2048-IMM for a building or 2048-M for shares in a property-rich company. Because the British treaty gives France a taxing right with credit rather than an exemption, your Leeds sale is not exempt in France, so the 2048-IMM filing applies; conversely, a gain that is exempt in France needs no 2048 return on top of form 2047. There is no French notaire (the public officer who normally computes and collects the gain on French conveyances) on a Leeds completion, so you or your adviser file the 2048-IMM directly and pay the French balance shown, before reporting the same gain again on the annual return through the foreign-income annex, form 2047, alongside the main 2042 return.
Build the file as if both administrations will ask for it, because on cross-border sales they often do within the same year. Keep the English purchase deed and completion statement, the sale particulars, every invoice for structural works with proof of payment, the dated euro conversion used, the HMRC 60-day submission receipt and payment confirmation, the filed 2048-IMM with its payment proof, and the later 2047 and 2042 figures showing the credit claimed. Where the property was jointly owned, each owner reports their share on each side, and the British guidance carries a dedicated section for jointly held property, so mirror the split exactly between the two returns rather than improvising a different fraction in each country. Where the sale follows a move back to Britain mid-year, residence for the year of sale decides everything, and the analysis in our dual-residence guide applies before any computation begins.
When the French assessment (avis d’imposition, the tax bill notice) arrives and the figures look wrong, the challenge path is administrative first and judicial second, with peremptory time limits (délais de recours). The claim (réclamation, the written complaint to the administration) must reach the tax office by a fixed date: “Pour être recevables, les réclamations relatives aux impôts autres que les impôts directs locaux et les taxes annexes à ces impôts, doivent être présentées à l’administration au plus tard le 31 décembre de la deuxième année suivant celle, selon le cas : a) De la mise en recouvrement du rôle ou de la notification d’un avis de mise en recouvrement ; b) Du versement de l’impôt contesté lorsque cet impôt n’a pas donné lieu à l’établissement d’un rôle ou à la notification d’un avis de mise en recouvrement ; c) De la réalisation de l’événement qui motive la réclamation.” In English: to be admissible, claims about taxes other than local direct taxes must reach the administration by 31 December of the second year following either the collection of the tax roll, the payment of the contested tax where no roll was issued, or the event grounding the claim. Typical winning points on these files are concrete: the administration ignored documented acquisition costs or works, applied no holding-period relief or the wrong start date, computed the credit on a net figure inconsistent with the British assessment, refused any credit although British tax was effectively and definitively paid, or charged social levies at a rate or base the notices do not support. Each point must attach its proof, because the butoir arithmetic means a one-line correction to the French base moves the credit ceiling euro for euro.
If the administration rejects the claim expressly or stays silent for six months, the dispute moves to the administrative court (tribunal administratif, the first-instance court for tax disputes): “L’action doit être introduite devant le tribunal compétent dans le délai de deux mois à partir du jour de la réception de l’avis par lequel l’administration notifie au contribuable la décision prise sur la réclamation”, with the taxpayer free to go to court once the six-month silence period expires without a reply. In English: proceedings must be brought within two months of receiving the administration’s decision on the claim, and the taxpayer may apply to the court as soon as six months have passed with no decision. Alongside or instead of domestic litigation, the treaty offers its own track: a resident who considers that the actions of one or both countries tax them contrary to the convention may present the case to the competent authority of their resident country, and the case must be presented within three years of the first notification of the taxation challenged as contrary to the convention. The mutual agreement procedure (procédure amiable, the treaty negotiation between the two tax authorities) is particularly suited to credit mismatches where each country insists the other should yield, and running it does not suspend the domestic deadlines, so file the domestic réclamation first and treat the treaty track as a parallel remedy rather than a substitute.
Conclusion
Selling a British buy-to-let from a French home means accepting two lawful taxations and organising one relief. The United Kingdom taxes the gain where the property stands and demands its money within 60 days of completion at 18% or 24% after the £3,000 allowance. France taxes the same gain because your domicile fiscal is in France, computing 19% income tax plus 17.2% social levies on the net gain after holding-period relief, with full income-tax exemption at twenty-two years and full social-levy exemption at thirty. The treaty then obliges France, and not the United Kingdom, to eliminate the double taxation through a credit equal to the British tax but capped at the French figure, the butoir that decides every file. File the British 60-day return, file the French 2048-IMM within the month, report on 2047 at the annual return, keep every deed and receipt with the euro conversion, and challenge by 31 December of the second year if the arithmetic is wrong, with the court at two months and the treaty procedure at three years behind it. Handled in that order, the Leeds sale produces one economic burden shared between two treasuries rather than two full bills on a single profit.