You have settled in France after Brexit, you are now French tax resident, and you have just sold — or are about to sell — the house you kept in Britain. Two tax offices immediately claim a share: HM Revenue and Customs in the United Kingdom taxes the gain because the bricks stand on British soil, and the French administration fiscale (tax administration) taxes the same gain because, as a French resident, you are taxable on your worldwide income. This double claim alarms many British sellers, and the calendar makes it worse: the United Kingdom demands its return within 60 days of completion, while France requires its own declaration within a month of the sale and then taxes the gain again the following year, with a treaty credit to cancel the overlap. Get the order, the paperwork or the arithmetic wrong and you pay twice, or you pay penalties on top. This guide explains, for a British reader living in France, who taxes what when a French resident sells a British home, how the Franco-British tax treaty of 19 June 2008 divides the bill, how to calculate each side, which forms and deadlines apply on each side of the Channel, and how to challenge a French assessment that ignores the British tax you have already paid.
I. Why France taxes your British sale and why the United Kingdom taxes it too
A. Are you a French tax resident when you sell your UK house, and why does France tax a sale in Britain?
Everything turns on one preliminary question: were you fiscalement domicilié en France (fiscally domiciled in France) on the day you sold the British property? French domestic law answers with article 4 B of the Code général des impôts (General Tax Code, the main French tax statute): “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” (in English: persons are regarded as having their fiscal domicile in France within the meaning of article 4 A where they have in France their household or the place of their main stay). In practice the French tax office looks at where your family home is, where you spend most nights of the year, and where your centre of economic interests sits. A British national who rents or owns a main home in Lyon, whose children attend a French school, and who spends more than 183 days a year in France will almost always be treated as French tax resident, even while keeping a British passport and a house in Manchester that is now let or empty. The 183-day marker is only a guideline, not a rule: a person can be French resident with fewer days if the family household, the foyer, is in France, and can remain non-resident despite long stays if the household stayed in Britain. Keep boarding passes, utility bills, school certificates and the French housing lease or title deed, because the service des impôts des particuliers, the local personal tax office often shortened to SIP, asks for them whenever residence is disputed.
Once French residence is established, France taxes the sale of the British house under the same article that taxes French sales. Article 150 U of the Code provides: “les plus-values réalisées par les personnes physiques ou les sociétés ou groupements qui relèvent des articles 8 à 8 ter , lors de la cession à titre onéreux de biens immobiliers bâtis ou non bâtis ou de droits relatifs à ces biens, sont passibles de l’impôt sur le revenu dans les conditions prévues aux articles 150 V à 150 VH” (in English: capital gains realised by individuals or by companies or groupings falling within articles 8 to 8 ter, on the sale for consideration of built or unbuilt immovable property or of rights relating to such property, are liable to income tax under the conditions laid down in articles 150 V to 150 VH). The gain is computed under article 150 V, which states: “La plus ou moins-value brute réalisée lors de la cession de biens ou droits mentionnés aux articles 150 U à 150 UC est égale à la différence entre le prix de cession et le prix d’acquisition par le cédant.” (in English: the gross gain or loss realised on the sale of property or rights mentioned in articles 150 U to 150 UC is equal to the difference between the sale price and the purchase price paid by the seller.) Acquisition costs, documented improvement works and transfer duties can be added to the purchase price within strict limits, and a taper relief for length of ownership then reduces the taxable base year by year until full exemption from income tax after 22 years of ownership and from social charges after 30 years. The full rate structure combines 19 per cent income tax with 17.2 per cent prélèvements sociaux (social levies on capital income), and the social side follows automatically once residence is French, because article L136-6 of the Code de la sécurité sociale (Social Security Code) provides: “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” (in English: individuals fiscally domiciled in France within the meaning of article 4 B of the General Tax Code are liable to a contribution on capital income assessed on the net amount taken into account for income tax). A French resident therefore pays the social levies on the British gain in full, unlike a non-resident who was taken out of part of that charge by European case law. The Court of Cassation confirmed the other side of that logic for residents in its judgment of 25 September 2025, no. 22-24.634, holding that counting a French resident cross-border worker’s capital income in the assessment base “ne porte pas atteinte à l’égalité de traitement et à la liberté de circulation des travailleurs” (in English: does not infringe equal treatment or the free movement of workers) (Cass. 2nd civil chamber, 25 September 2025, no. 22-24.634). As a French resident you should expect the same treatment: no European exemption from the French social levies on your British gain.
The mirror image for the opposite direction, a British resident selling a French house, sits in article 244 bis A, which opens: “Sous réserve des conventions internationales, les plus-values, telles que définies aux e bis et e ter du I de l’article 164 B” (in English: subject to international treaties, capital gains as defined in article 164 B), with the treaty again deciding the final charge. Two traps catch British sellers at this stage. The first is believing the British house counts as a main home for French purposes. The French exemption for the sale of the main home covers only property described by article 150 U as: “Qui constituent la résidence principale du cédant au jour de la cession” (in English: property which constitutes the seller’s main residence on the day of sale) (CGI, art. 150 U). A house in Leeds cannot be your main residence on the day of sale if your household lives in Bordeaux; the exemption belongs to the French home you occupy, not to the British one you kept. The Council of State underlined how strictly judges test that occupation in a decision of 14 March 2025, no. 474943, where sellers claimed a newly built house had become their main home for a few months before sale: the appeal court had refused the exemption because it doubted their intention, and the Council of State annulled that ruling, holding that “alors qu’il lui revenait seulement d’apprécier les conditions dans lesquelles ils avaient occupé effectivement ce bien, la cour a commis une erreur de droit” (in English: whereas it was only required to assess the conditions in which they had actually occupied the property, the court committed an error of law), adding in its operative part that “L’arrêt de la cour administrative d’appel de Versailles du 11 avril 2023 est annulé.” (in English: the judgment of the Versailles administrative court of appeal of 11 April 2023 is annulled.) (Council of State, 14 March 2025, no. 474943). The lesson for a British seller runs in the opposite direction but with the same strictness: only genuine, demonstrable occupation as your main household on completion day opens the exemption, and a British second property held while your family lives in France will not qualify. The second trap is assuming Brexit changed the treaty. It did not: the convention signed on 19 June 2008 and published in France by Decree no. 2010-20 of 7 January 2010 still allocates taxing rights between the two states, and its commentary is maintained on the French tax administration’s official doctrine database at BOFiP, France–United Kingdom treaty. Under that treaty, gains on immovable property may be taxed in the state where the property stands, which is the United Kingdom here, while France as the residence state taxes the worldwide gain and then relieves the overlap with a credit. The treaty overrides domestic law where they conflict, a primacy the courts apply routinely: in a 2 April 2025 ruling on treaty characterisation of property-company results, the commercial chamber approved the appeal court for having held that “les résultats de ces sociétés civiles immobilières devaient être imposés en France” (in English: the results of those property companies had to be taxed in France) under the applicable treaty provision (Cass. commercial chamber, 2 April 2025, no. 23-14.568). Read your treaty position first, then the domestic articles: that order decides everything that follows.
B. How much UK Capital Gains Tax do you pay first, and what is the 60-day trap?
The United Kingdom has taxed non-residents on British residential property sales since 2015, so living in France gives you no shelter from HM Revenue and Customs. The British gain is broadly the sale price minus purchase price and allowable costs, with its own reliefs: periods when the house was your only or main home, including the final months of ownership, and letting relief in narrow surviving cases can reduce the British figure, and an annual exempt amount shelters a slice of each individual’s gains. The tax rate then depends on your British income-tax band in the year of sale. The official GOV.UK guidance states the rule in plain terms: higher and additional-rate taxpayers pay 24% on their gains from 6 April 2026, while gains falling within the basic Income Tax band are charged at 18% (see Capital Gains Tax rates). Read that page and the guide to reporting a UK property sale before exchanging, because the band in the year of completion, not the year you moved to France, sets the percentage.
The deadline is the real danger. GOV.UK warns that any Capital Gains Tax due on UK residential property must be reported and paid within 60 days of completing the sale. Completion means the day ownership legally passes, not the day contracts are exchanged, and the 60-day count includes weekends. You file through the UK Property reporting service, estimate the gain, and pay on account within that window; the amount is later reconciled on your UK Self Assessment return. Miss the window and interest runs from day 61, with late-filing penalties added at six and twelve months even where the final liability turns out to be small. For a seller living near Paris or in Provence, practical friction multiplies the risk: the conveyancer in England sends the completion statement by email while you are on holiday, the funds arrive in euros after conversion, and nobody reminds you that a return is due in London within two months. Diarise the deadline on exchange day, instruct your British solicitor or conveyancer in writing to send the completion statement within 48 hours of completion, and file the UK return even if you believe reliefs wipe out the gain, because the filing itself protects you and the paperwork becomes the evidence France will demand. Keep the completion statement, the original purchase deed and price, invoices for allowable improvements, records of periods of occupation and letting, the Home Office or HMRC correspondence showing the tax paid, and proof of the payment date: the French tax office will ask for each of them when it computes your treaty credit, and without the British assessment and payment receipt the credit can be refused.
A worked sketch shows why the British step matters first. Suppose you bought a two-bedroom flat in Bristol in 2016 for 220,000 pounds, spent 15,000 pounds on a documented extension, and complete the sale in November 2026 for 310,000 pounds. The rough British gain before reliefs is around 75,000 pounds; after the annual exempt amount and any main-residence relief for years you lived there, the taxable slice might fall to 50,000 pounds, taxed at 18 or 24 per cent depending on your band, so roughly 9,000 to 12,000 pounds of UK tax paid within 60 days. France will then compute its own gain in euros at the Banque de France rate on the relevant dates, apply its own taper, its 19 per cent plus 17.2 per cent, and give a credit for the British tax within the limit of the French tax on that gain. If the British tax exceeds the French tax, the surplus is simply lost; France never refunds foreign tax above its own charge. That asymmetry explains the planning point sellers miss: realising the sale in a year when your French taxable income is lower, or after another year of French taper has accrued, can change the French figure against which the credit is capped, while nothing changes the British deadline. Readers facing the mirror situation, leaving France and later selling the former French home, meet the same credit logic in reverse, with France as the property state and Britain as the residence state giving relief.
II. How France relieves the double bill and how to challenge it
A. How do you declare the UK sale in France and how is the treaty credit calculated?
The French tax administration’s official guidance for exactly this situation is reassuringly clear. It explains that a French resident selling a building abroad is, absent a treaty with the property state, taxed just as if the property stood in France. Where a treaty exists, as with the United Kingdom, the property state taxes first and France relieves the overlap: a credit is deducted from the French tax, equal under the treaty terms to the French tax computed on the gain or to the foreign tax, capped at the French tax. Read the full official page on property outside France or seller outside France before filing, because it also lists the forms and the one-month clock described below.
In practice the declaration runs in three layers. First, within one month of the sale, you file form 2048-IMM, the déclaration de plus-value immobilière (immovable-gain return), with the tax office of your French home, unless the gain is fully exempt in France under the treaty, in which case that form is not required but the income must still be reported as described next. Attach the British completion statement, the purchase deed, works invoices, the HMRC calculation and proof of the UK payment. Second, the following spring, you report the gain on form 2047, the return for foreign-source income, and carry it to the main return 2042, so the gain enters your French taxable income with the credit alongside. Third, the tax office computes the French tax on that gain at 19 per cent plus 17.2 per cent social levies after taper, then imputes the credit equal to the lower of the British tax actually paid and the French tax on the gain. A Council of State decision of 28 February 2025, no. 491788, shows the mechanism working, and failing, on real numbers: a French-domiciled taxpayer declared foreign property income where a French-domiciled taxpayer with foreign property income where, in the Council’s words, “se sont prévalus d’un crédit d’impôt conventionnel égal à l’impôt sur le revenu français correspondant” (Council of State, 28 February 2025, no. 491788) (in English: claimed a treaty tax credit equal to the corresponding French income tax). The file concerned a declared gain of about 1.65 million euros with a claimed French-tax credit of 313,110 euros. The administration answered, again in the decision’s words, that “l’administration fiscale a limité ce crédit d’impôt au montant de l’impôt américain qu’ils avaient supporté à ce même titre” (Council of State, 28 February 2025, no. 491788) (in English: limited the credit to the American tax borne under the same head), capping it at 205,400 euros. The taxpayers challenged the top-up through the administrative courts, and the Council of State finally held that “Le pourvoi du ministre de l’économie, des finances et de la souveraineté industrielle et numérique est rejeté.” (Council of State, 28 February 2025, no. 491788) (in English: the minister’s appeal is dismissed). The treaty, the amounts and the cap decided the case: claim the full credit, prove the foreign tax pound by pound, and expect the office to cap it at the foreign tax actually paid.
Two refinements complete the calculation. Currency comes first: convert the British purchase price, works and sale price into euros at the official rates on each relevant date and keep the printouts, because a 5 per cent swing in sterling can move the French gain by tens of thousands of euros on a London sale. Taper comes second: France applies its own ownership clock from the purchase date shown on the British title, regardless of when you moved to France, so a flat held since 2010 reaches near-full income-tax relief by the late 2020s while the British computation gives no taper at all. Do not confuse the two systems when you reconcile them. Note also the high-gain surtax in article 1609 nonies G of the Code, the taxe sur les plus-values de cessions d’immeubles (surtax on large property gains), which the Council of State case above applied alongside income tax and social levies; check whether your net taxable gain crosses its thresholds, because the treaty credit does not automatically absorb it. Finally, file even when you think nothing is due: the 2048-IMM omission carries its own penalty, and the 2047 omission blocks the credit. A seller who files the British 60-day return on time but forgets the French one-month return has solved only half the problem and created the evidence gap the French office uses to reassess.
B. What if the French bill ignores your British tax, and how do you challenge it in Paris and beyond?
The most common French error is simple: the assessment arrives with the full 19 per cent plus 17.2 per cent and no credit, because the office never linked your 2048-IMM to the 2047, or because it disallowed the British proof as insufficient. The second most common error is subtler: the office accepts a credit but caps it wrongly, using an exchange rate of its choosing, refusing part of the British tax as relating to a different year, or treating a British penalty or interest as tax. The third error concerns residence itself: the office taxes you as a French resident on the worldwide gain while you maintain you were still British resident on completion day, or vice versa, and the treaty tie-breaker for dual residence decides the outcome. Each error has its own remedy, but all remedies share one foundation: the paper file. Assemble now the file you will need later: the British purchase and sale contracts with completion statement, Land Registry entries, works invoices with bank transfers, letting agreements and rent statements if the property was let, the HMRC 60-day calculation and payment receipt, French avis d’imposition (tax notices) for the two surrounding years, proof of the family home in France, and a day-count table with travel evidence for the year of sale. The Council of State’s residence-principle ruling above shows why contemporaneous proof beats later assertions: judges assess how the property was actually occupied, not what the seller intended, and they annul decisions built on the wrong test.
The challenge follows the standard French tax-dispute ladder, the contentieux fiscal. Start with a réclamation contentieuse (formal tax claim) to the SIP that issued the notice, sent by tracked post or through your online espace particulier (personal account) on impots.gouv.fr, within the claim deadline shown on the notice and in any event before 31 December of the second year following the assessment. Ask expressly for discharge or reduction of the specific supplementary tax and social levies, quantify the credit claimed in euros with the exchange-rate source, list each enclosed proof, and request a stay of payment, the sursis de paiement, if enforced recovery has begun. If the office rejects expressly or stays silent for six months, which counts as an implied rejection, appeal to the tribunal administratif (administrative court) of your home: for Paris that is the Paris administrative court, with Montreuil, Versailles, Cergy-Pontoise and Melun covering the inner and outer suburbs, so check the notice’s appeal paragraph rather than guessing. The court re-examines the computation, the credit cap and the residence question in full, and the treaty-credit arithmetic from the 2025 Council of State decision gives the template: declare the gain, prove the foreign tax, cap the credit, discharge the surplus. An adverse first-instance judgment can go to the cour administrative d’appel (administrative court of appeal), in Paris that is the Paris court, and points of law can reach the Council of State, whose recent property-gain rulings show it does not hesitate to annul appeal judgments built on the wrong legal test. Interest for late payment, the intérêt de retard, and penalties can themselves be challenged where you relied in good faith on the treaty position or where the office delayed: ask the judge to moderate them and to offset any British overpayment evidence.
Paris practice adds three points worth knowing before you file. First, Île-de-France tax offices handle a large British caseload and process 2048-IMM forms for foreign sales through designated property-tax units, so address the one-month return exactly as the impots.gouv.fr page directs and keep the stamped receipt; a return sent to the wrong SIP is treated as never filed until it is re-routed. Second, the competent court follows your French address, not the location of the British house, so a seller in the 16th arrondissement appeals in Paris while a seller in Boulogne-Billancourt or Saint-Germain-en-Laye appeals in Versailles or Cergy, with different backlog times; file early in the deadline rather than on the last day. Third, gather the British evidence in the form French judges expect: a completion statement alone rarely suffices, so add Land Registry title extracts, the solicitor’s ledger, the HMRC account printout showing the 60-day payment allocated to the gain, and a sworn French translation, a traduction assermentée, of any English-only document you intend to rely on, because an untranslated bundle invites the reporting judge to disregard it. With that file, most credit disputes settle at the claim stage: the office corrects the imputation, issues a dégrèvement (tax relief order) for the excess, and adds statutory interest on the refund. If it does not, the file you built on day one becomes the court bundle on day 300, and the treaty-credit arithmetic does the rest.
Conclusion
Selling a British home while living in France means paying in the right order: British tax within 60 days of completion at 18 or 24 per cent, French declaration within a month on form 2048-IMM with carry to forms 2047 and 2042, French tax at 19 per cent plus 17.2 per cent social levies after taper, and a treaty credit capped at the lower of the two charges. Residence under article 4 B decides whether that worldwide charge applies at all; the treaty of 19 June 2008 decides which state yields; the Council of State’s 2025 rulings show judges enforcing both the occupation test for exemptions and the capped-credit arithmetic to the euro. Build the file before completion, file both returns on time, convert currencies with sourced rates, and challenge any French bill that omits the credit through a reasoned claim and, if needed, the administrative court of your home. The double bill is then reduced to what the treaty allows: one economic gain, two computations, a single net charge.