This is the disputes companion to our main guide on selling your English house as a French resident, which sets out the full mechanics of the British and French charges and the treaty credit. This companion starts where that guide stops: when the French assessment arrives and it is wrong. You have settled in France, you pay your French taxes, your children go to a French school, and this spring you finally sold the house you still owned in Manchester, Bristol or Bromley. Then two letters arrive within weeks of each other. HMRC wants a capital gains return within 60 days of completion, and your French tax office wants the same gain on your next French income tax return. You are asking the obvious question: do I really have to pay twice on the same sale, and if not, who gives me the credit and how do I prove it. This article answers that question from end to end. It explains why France taxes the sale of a house that stands in England, how the United Kingdom taxes it first and on what terms, how the Franco-British double tax treaty of 19 June 2008 divides the bill between the two countries, which two filings protect your treaty credit, and how to challenge a French assessment that ignores the British tax you have already paid.

I. Why France taxes your English sale and how the United Kingdom taxes it first

A. Living in France means France taxes your worldwide property gain

French tax residence is the key that opens the whole file. You are treated as having your domicile fiscal in France, your French tax home, as soon as you meet any one of the tests in article 4 B of the Code général des impôts, the French tax code. The first test is the one that catches almost every British settler: “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”, which means persons who have in France their foyer, their family home, or the place of their main stay. If your family lives with you in Lyon, Bordeaux or Paris, or if you simply spend more of the year in France than anywhere else, you are a French tax resident even though you kept your British passport and even though the house you sold stands in England. The fact that the building is outside France changes nothing about your residence, because French residents are taxed on their worldwide income and gains, whereas the source rule in article 164 B of the same code, which lists as French-source income “Les revenus d’immeubles sis en France ou de droits relatifs à ces immeubles”, meaning income from buildings situated in France, is the rule for non-residents, not for you.

Once residence is established, the French gain on your English house is computed under the ordinary property gains regime, the plus-value immobilière des particuliers, meaning capital gains on property realised by private individuals. Article 150 U of the Code général des impôts provides that “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”, which means gains realised by individuals on the sale for consideration of built or unbuilt property are liable to income tax, the impôt sur le revenu, under the conditions of articles 150 V to 150 VH. The starting point of the computation is given by article 150 V: “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”, meaning the gross gain equals the difference between the sale price and the purchase price paid by the seller. In practice the purchase price you declare is not the bare figure on the old English conveyance. The official service-public guide explains that the price is increased by acquisition costs, meaning stamp duty, legal and agency fees on purchase, for their actual proven amount or for a flat 7.5 percent of the purchase price, and by building, reconstruction, extension or improvement works for their actual proven amount or for a flat 15 percent of the purchase price where you held the property for more than five years, as set out on service-public.fr. Keep every invoice, because the flat rates are a fallback and the tax office will ask for proof the moment the figures look generous.

Three further French features decide the size of the bill. First, the main-home exemption does not help you here. The sale of your résidence principale, your main home, is exempt, but the exempt home is the one in France where you actually live, not the English house you kept and let or left empty. Second, the holding-period allowance, the abattement pour durée de détention, reduces the taxable gain the longer you owned the property: 6 percent per year from the sixth to the twenty-first year of ownership and 4 percent for the twenty-second year, which produces full exemption from income tax after twenty-two years of ownership, while the parallel allowance for social charges runs at 1.65 percent per year then 1.6 percent and 9 percent slices to give full exemption after thirty years, as detailed on service-public.fr. Third, the rates combine two layers: the net gain bears income tax at 19 per cent, with social charges on top, the prélèvements sociaux, meaning social charges on investment and property income, at 17.2 per cent, as the same official guide confirms. The social charge is not a mistake or a double count. Article L. 136-6 of the Code de la sécurité sociale, the social security code, states 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”, meaning individuals fiscally domiciled in France are liable to a contribution on their capital income assessed on the net amount used for income tax. A worked example makes the arithmetic concrete: a gain of 100,000 euros after allowances, on a house held twelve years, bears 19,000 euros of income tax and 17,200 euros of social charges before any treaty credit, which is why the credit for British tax examined below is worth fighting for.

B. The United Kingdom taxes the bricks first and wants its return within 60 days

The United Kingdom does not lose its taxing right just because you moved to France. Under the treaty, gains on immovable property stay taxable where the property stands, so HMRC taxes the sale of your English house first and France then gives relief. The British compliance clock is brutally short and it starts on completion, not on the tax year end. The official HMRC guidance requires any Capital Gains Tax due on UK residential property to be reported and paid within 60 days of completion, warning that interest and a penalty apply for late filing, as published on gov.uk. This is the UK capital gains tax return on UK property, filed through the HMRC online account, with the tax paid as part of the same 60-day filing. Miss the deadline and interest runs from the day after, with fixed and daily penalties on top, so the return must be prepared while the conveyancer still holds the completion statement, not months later when the French return falls due.

The British rates you face are the residential-property capital gains rates. HMRC’s rates page puts the charge at 24 per cent for higher and additional-rate taxpayers and at 18 per cent within the basic-rate band, rising to 24 per cent above it, for gains from 6 April 2026, as published on gov.uk. Your private residence relief, the British equivalent of the main-home exemption, will normally cover only the years you actually lived in the house plus the final months of ownership allowed by the rules, and lettings relief is now narrow, so a former family home that you kept for years after moving to France very often produces a real taxable gain in the United Kingdom. That British bill is not money lost. It is the payment that generates your French treaty credit, which is why paying HMRC late, or paying the wrong figure, damages your French position as well. Every pound of British tax must be documented, because the French tax office will only credit tax that was actually levied in accordance with the treaty, and the Conseil d’Etat, the supreme administrative court, polices that boundary strictly, as the second part of this article shows.

The treaty rule that organises this sharing is simple to state and technical to apply. The Franco-British convention gives the state where the property stands the primary right to tax, and it makes the residence state, France in your case, eliminate the resulting double taxation by credit. The French tax administration’s official commentary, the BOFiP, explains for this exact convention that in this situation it falls to France to eliminate double taxation under article 24 paragraph 3 of the convention, and that the tax credit equals the British tax for disposals of real property and property-rich entities, as published in BOI-INT-CVB-GBR-10-20. The general treaty formula behind that commentary is the one the Conseil d’Etat recalls case after case: gains on immovable property situated in one state are taxable there, and the credit given by France cannot exceed the French tax on the same income. In the words of article 13 of the comparable conventions, “Les gains provenant de l’aliénation de biens immobiliers situés dans un Etat contractant sont imposables dans cet Etat”, meaning gains from the disposal of immovable property situated in a contracting state are taxable in that state, while the credit rule provides that “toutefois, ce crédit d’impôt ne peut excéder le montant de l’impôt français correspondant à ces revenus”, meaning the credit may not exceed the French tax on that income, as restated in Conseil d’Etat, 28 February 2025, no. 491788, available on Légifrance. Two consequences follow for your file. Where the British tax is lower than the French tax on the same gain, you pay HMRC in full and you pay the French tax office the difference. Where the arithmetic is reversed, France keeps nothing on the income-tax layer but it never refunds the surplus British tax, and the social charges layer follows its own logic, examined in the second part.

II. How to declare on both sides and challenge the bill when it is wrong

A. The two filings that secure your treaty credit and the proof file that goes with them

Your protection rests on two filings made in the right order with matching figures. First, the British 60-day return described above, because without an HMRC assessment and proof of payment there is no British tax to credit. File it through your HMRC online account as soon as completion funds move, keep the submission receipt, the computation schedule and the payment reference, and reconcile the sterling gain with the euro figures you will declare in France using the exchange rate at the date of disposal. Second, the French annual return the following spring: the worldwide gain goes on the foreign-income schedule, the déclaration des revenus encaissés à l’étranger, form 2047, with the treaty credit claimed on the income-tax adjustment schedule, form 2042-C, against the income-tax layer computed at 19 percent after the holding-period allowance. The credit claimed must equal the British tax actually paid on that gain and can never exceed the French income tax on the same gain, which is exactly the cap the Conseil d’Etat enforced in its 28 February 2025 decision: the taxpayers had declared a property gain of 1,647,943 euros and claimed a treaty credit equal to the corresponding French tax of 313,110 euros, the administration cut the credit to the 205,400 euros of foreign tax actually borne, litigation followed, and the Conseil d’Etat closed the case with “Le pourvoi du ministre de l’économie, des finances et de la souveraineté industrielle et numérique est rejeté”, meaning the minister’s appeal is dismissed, in Conseil d’Etat, 28 February 2025, no. 491788, on Légifrance. The lesson is practical rather than philosophical: claim the full British tax you paid, capped at the French tax, and attach the proof, because an uncapped or unproven credit is the first thing a contrôle sur pièces, a desk audit, will strike out.

Build one bilingual proof file and use it for both administrations. It should contain the English transfer deed and completion statement with the exact completion date, the original purchase deed with the price in pounds and the historical exchange rate, invoices for acquisition costs and works with a note explaining why you chose actual costs or the 7.5 and 15 percent flat rates, the letting history if the house was rented, with dates you lived in it for the British reliefs, the HMRC 60-day submission receipt and payment confirmation with the computation, and a one-page reconciliation converting every sterling figure into euros with sources for the rates used. Three consistency traps destroy files every year. The completion date on the French return must match the one on the HMRC return, because the 60-day clock and the French taxable year both turn on it. The sterling-to-euro conversion must use one stated method throughout, because mixing Bank of England spot rates with your bank’s applied rates creates phantom differences the computer will flag. And the gain pattern must be coherent across the two countries: if you tell HMRC the house was your main home for relief and tell France it was a secondary asset for allowances, both statements can be true, but only if the dates of occupation are identical on both sides, so write one timeline and file it everywhere.

B. When the French bill is wrong and how to fight it without losing the credit

French assessments on foreign property gains go wrong in predictable ways, and each error has its own remedy. The most expensive is the missing or truncated treaty credit: the avis d’imposition, the tax assessment notice, shows the full 19 percent with no credit, or a credit cut below the British tax you paid. The second is a miscomputed allowance, usually because the ownership period was counted from the wrong deed or because works were disallowed for lack of invoices. The third is social charges applied where the treaty or European rules remove them, or applied twice on figures already taxed. The fourth is a residence challenge, where the tax office treats you as still British-resident and pushes your file toward the non-resident levy instead of the resident regime. Do not let that reclassification pass unchallenged if your life is in France. Article 244 bis A of the Code général des impôts imposes, “Sous réserve des conventions internationales”, meaning subject to international treaties, on gains “réalisées par les personnes et organismes mentionnés au 2 du I lors de la cession des biens ou droits mentionnés au 3”, meaning realised by the listed persons on the listed assets, a specific levy, the prélèvement, whose mechanism the Conseil d’Etat summarised as follows: “En application du paragraphe I de l’article 244 bis A du code général des impôts, dans sa rédaction applicable à l’imposition en litige, les personnes physiques qui ne sont pas fiscalement domiciliées en France au sens de l’article 4 B du même code, sont soumises, sous réserve des conventions internationales, à un prélèvement spécifique sur les plus-values résultant, notamment, de la cession de biens immobiliers”, meaning individuals not fiscally domiciled in France are subject, subject to treaties, to a specific levy on gains including those from property disposals, in Conseil d’Etat, 12 February 2020, no. 415475, on Légifrance. That levy is the mirror image of your case: it hits the person who left France and sells a French building, while you, resident in France selling an English building, belong under the article 150 U computation with the full allowance scale and the treaty credit. If your notice looks like a non-resident levy, the residence analysis in the first part of this article is your first exhibit.

The procedural route is the same whatever the error. Start with a réclamation, a formal complaint to the tax office, sent within the statutory time limit from the assessment notice, setting out each correction with its exhibit number from your proof file: residence evidence for the foyer test, deeds and invoices for the gain, HMRC receipts for the credit, rate tables for the allowances. Article L. 190 of the Livre des procédures fiscales, the tax procedure code, gives this step its legal force: “Les réclamations relatives aux impôts, contributions, droits, taxes, redevances, soultes et pénalités de toute nature, établis ou recouvrés par les agents de l’administration, relèvent de la juridiction contentieuse lorsqu’elles tendent à obtenir soit la réparation d’erreurs commises dans l’assiette ou le calcul des impositions, soit le bénéfice d’un droit résultant d’une disposition législative ou réglementaire”, meaning complaints about taxes and penalties of any kind fall under contentious jurisdiction where they seek to repair errors in the base or computation or to obtain a right under statute or regulation. If the office rejects the claim expressly or stays silent past the deadline, appeal to the tribunal administratif, the administrative court for tax disputes, within two months, asking the judge to discharge the excess and to recognise the credit. Keep paying or securing the disputed amount in the meantime where required, because delay itself is priced. Article 1727 of the Code général des impôts provides that “Toute créance de nature fiscale, dont l’établissement ou le recouvrement incombe aux administrations fiscales, qui n’a pas été acquittée dans le délai légal donne lieu au versement d’un intérêt de retard”, meaning any tax debt not paid on time bears late-payment interest, and article 1728 adds that “Le défaut de production dans les délais prescrits d’une déclaration ou d’un acte comportant l’indication d’éléments à retenir pour l’assiette ou la liquidation de l’impôt entraîne l’application, sur le montant des droits mis à la charge du contribuable ou résultant de la déclaration ou de l’acte déposé tardivement, d’une majoration de”, meaning late filing triggers a surcharge on the duties owed, set at “10 % en l’absence de mise en demeure”, meaning 10 percent where no formal demand was first served. File late in either country and the surcharge eats the credit you fought to obtain, so diary the 60-day British deadline and the French return deadline together from the day of completion.

Conclusion

A British national living in France who sells an English house is taxed twice in procedure but once in substance: HMRC taxes the gain where the bricks stand and must be reported and paid within 60 days of completion, while France taxes the same gain worldwide at 19 percent plus 17.2 percent social charges after holding-period allowances, then wipes out the French income-tax layer up to the British tax paid through the article 24 treaty credit. The file succeeds or fails on three disciplines: proving French residence under the foyer test so the full resident regime applies, computing the gain with documented purchase costs and the correct allowance years, and filing the British return first so the French credit rests on tax actually paid. Where the assessment ignores the credit, miscounts the years or misstates residence, the réclamation and then the tribunal administratif give you a structured path to correction, with the Conseil d’Etat’s credit jurisprudence behind you. Start the proof file on completion day, keep one timeline in both languages, and never let either deadline slip. For the complete mechanics of both charges and the credit, see our main guide to selling your English house as a French resident.