You keep a house in France, a current account in Britain, and a calendar that never quite matches either tax office. Then a letter arrives. The French administration treats you as resident and asks for tax on worldwide income. HMRC still treats you as resident in the United Kingdom. Sometimes both write in the same year, about the same pension, the same dividends or the same gain. After Brexit that collision is no longer softened by free movement. French domestic law does not wait for a visa stamp, and it does not wait for 183 days on a spreadsheet. It looks at your foyer (the home where your household actually lives), your work and the centre of your money. Only then does the France-UK tax treaty decide which of the two States may treat you as its resident if both claim you.

The 183-day story is the first trap. Spending fewer than six months in France does not, by itself, make you a non-resident if your family home is here. Spending more than six months here does not automatically settle the matter if you have no foyer in France. The second trap is to stop at French law: even when article 4 B of the Code général des impôts (the French tax code) points to France, article 4 of the convention of 19 June 2008 can still assign you to the United Kingdom. The third trap is silence. If you do not file, the administration may assess you of its own motion and add a 10%, 40% or 80% surcharge. What follows is the order the courts actually use: French tests first, treaty second, claim third.

I. Am I tax resident in France if I still have a UK home after Brexit?

A. The 183-day myth: foyer, main stay, work and the centre of your money

French income tax starts with a single idea: the domicile fiscal, the place of tax residence. Article 4 A of the Code général des impôts states, word for word: “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. Celles dont le domicile fiscal est situé hors de France sont passibles de cet impôt en raison de leurs seuls revenus de source française.” In plain English, a person whose tax residence is in France is taxable on all income, wherever it arises. A person whose tax residence is outside France is taxable in France only on French-source income.

Residence itself is defined by article 4 B of the same code, in force in its current wording since 16 February 2025. The opening tests read: “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 professionnelle, salariée ou non, à moins qu’elles ne justifient que cette activité y est exercée à titre accessoire ;” and, after the special rule for directors of very large French companies, “c. Celles qui ont en France le centre de leurs intérêts économiques.” One criterion is enough. You do not have to tick all three boxes. The same paragraph then yields to treaties: “Les personnes qui satisfont à l’un au moins des critères fixés aux a à c du présent 1 ne peuvent toutefois pas être considérées comme ayant leur domicile fiscal en France lorsque, par application des conventions internationales relatives aux doubles impositions, elles ne sont pas regardées comme résidentes de France.”

The official public guide on service-public.fr (sheet F62, updated 1 January 2026) presents the same four ideas for a lay reader: the household is in France; the main stay is in France; the main work is in France; the centre of economic interests is in France. On the main stay it describes residence as a stay of at least 183 days in the year, more than six months. That figure is useful as a rule of thumb. It is not the whole law. The Conseil d’État (France’s highest administrative court) has said, repeatedly, that the 183-day count is only a fallback.

In Conseil d’État, 9th and 10th chambers combined, 21 June 2022, no. 449408, the court quoted article 4 B and then fixed the meaning of foyer: “Pour l’application de ces dispositions, le foyer s’entend du lieu où le contribuable habite normalement et a le centre de ses intérêts familiaux, sans qu’il soit tenu compte des séjours effectués temporairement ailleurs en raison des nécessités de la profession ou de circonstances exceptionnelles, et que le lieu du séjour principal du contribuable ne peut déterminer son domicile fiscal que dans l’hypothèse où celui-ci ne dispose pas de foyer.” The family home is the place where you normally live and where your family interests are centred. Temporary stays elsewhere for work, or because of exceptional circumstances, do not move that home. The place of your main stay may fix tax residence only if you have no foyer at all.

That is why a British second-home owner who still has a spouse, a civil partner or children living in the French house can be treated as French-resident even if the passport stamps show fewer than 183 days. The French tax site puts the same point in administrative language: your foyer remains in France even if work takes you abroad for most of the year. If there is no household, residence is defined by the main stay. The site is impots.gouv.fr, Suis-je non-résident fiscal ?, updated 8 April 2026.

The Paris administrative court of appeal applied the same hierarchy to a taxpayer who tried to win on days alone. In CAA Paris, 5th chamber, 20 October 2023, no. 22PA00816, the court recalled that for a single taxpayer without dependants “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. Le lieu du séjour principal de ce contribuable ne peut déterminer son domicile fiscal que dans l’hypothèse où il ne dispose pas de foyer en France.” The taxpayer argued that he had lived 201 days in Israel and only 164 days in France. The court recorded that argument in these words: “M. B… soutient qu’il avait son domicile fiscal, au sens de ces mêmes dispositions, en Israël dès lors qu’il justifie y avoir habité durant 201 jours, et seulement 164 jours en France.” It then looked at the Paris flat, the domestic employee paid all year, the mail delivered there, and the gas and electricity use. The days in Israel did not move the foyer. The claim was rejected.

Work is the second independent test. Article 4 B 1 b treats you as French-resident if you carry on a professional activity in France, employed or not, unless you prove that the activity is only accessory. The public guide says the main activity is the one to which you devote the most actual time, or the one that gives you the bulk of your income. A British solicitor who still has a London practice but spends the working week in a Paris office, or a consultant whose clients and invoices are French, can meet this test even with a house in Kent. Conversely, occasional days of remote work from a holiday home, with the real job remaining in Britain, may be accessory. The burden of proving that the French activity is only accessory lies on the taxpayer.

The third test is the centre of economic interests: the place of your main investments, the seat of your affairs, or the place from which the greater part of your income comes. The Paris court of appeal applied that test to a film-maker with property in the United Kingdom and the United States. In CAA Paris, 9th chamber, 15 March 2018, no. 17PA01909, the court found that the French income (salaries, authors’ rights, and French property income, including through sociétés civiles immobilières, property-holding companies) came to 775,227 euros in 2010 and 148,228 euros in 2011, above the 141,329 euros and 144,071 euros from property in the United Kingdom and the United States. It held: “dans ces conditions M. B…doit être regardé comme ayant eu en France le centre de ses intérêts économiques, même s’il exerçait hors de France son activité professionnelle de tournage et de réalisation de films et même s’il détenait un patrimoine immobilier conséquent à l’étranger”. French economic centre, even though the filming was abroad and even though there was substantial property abroad. Under French law that single finding was enough. As section B shows, the same judgment then went on to the treaty, and the treaty produced the opposite result for worldwide tax.

Two practical consequences follow for a British reader. First, keep a file. The courts look at who lives in the house, school enrolment, the address on the identity document, council-tax type bills, bank statements, utility use, where the children sleep, where the spouse or partner actually lives, and where the larger part of income is paid. Second, do not treat a UK statutory residence test print-out as an answer to article 4 B. HMRC’s test, set out in the RDR3 guidance on GOV.UK, is a different legal machine. It can make you UK-resident in the same year in which France, applying article 4 B, also claims you. That is a dual-residence case, not a proof that France is wrong.

B. What if HMRC still treats me as UK resident? The France-UK treaty tie-breaker

When both domestic laws claim you, the convention of 19 June 2008, set out in English on GOV.UK, supplies a ladder. The Paris administrative court of appeal quoted article 4 of that convention in CAA Paris, 9th chamber, 15 March 2018, no. 17PA01909. After recording that a dual resident’s position is settled under paragraph 2, the court quoted the first rung: “cette personne est considérée comme un résident seulement de l’Etat contractant où elle dispose d’un foyer d’habitation permanent ; si elle dispose d’un foyer d’habitation permanent dans les deux Etats, elle est considérée comme un résident seulement de l’Etat avec lequel ses liens personnels et économiques sont les plus étroits (centre des intérêts vitaux)”. A British person whom France taxes solely as a non-resident on a French rental, and whom the United Kingdom taxes as a resident on worldwide income, is not a dual resident under the treaty. A person whom both States tax on worldwide income because each treats that person as resident is a dual resident. The tie-breaker then applies.

The same judgment continues the ladder at b): if the centre of vital interests cannot be determined, or if there is no permanent home in either State, the person is treated as a resident only of the State of habitual abode; then nationality; then, if need be, mutual agreement of the competent authorities. A permanent home available in only one State ends the analysis. Homes in both States take you to the centre of vital interests: the State with which personal and economic relations are closer. The English GOV.UK text uses the same ladder: permanent home, centre of vital interests, habitual abode, nationality, mutual agreement.

The courts refuse to jump straight to the treaty. In CAA Bordeaux, 4th chamber, 21 April 2026, no. 24BX01371, a recent judgment on a taxpayer who said he was resident in Hong Kong, the court restated the classic two-step: “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. Par suite, il incombe au juge de l’impôt, lorsqu’il est saisi d’une contestation relative à une telle convention, de se placer d’abord au regard de la loi fiscale nationale pour rechercher si, à ce titre, l’imposition contestée a été valablement établie et, dans l’affirmative, sur le fondement de quelle qualification.” French law first. The convention second, and only to see whether it blocks the French charge. Article 55 of the Constitution is the supremacy of treaties over statute. It does not turn the treaty into a free-standing charging provision.

The film-maker case already cited is the working example for a British dual home. After holding that French law made the taxpayer resident because of the centre of economic interests, the Paris court of appeal applied article 4 of the Franco-British convention. It recorded that he had declared and paid tax in both States, so he was a resident of both contracting States under paragraph 1. It then found that during the years in dispute he lived in London with his British partner, with whom he had a child born in the United Kingdom on 10 April 2011, and that he held two London properties valued at 2,400,000 euros and 1,615,000 euros, while his French wealth-tax declarations showed about 2 million euros. The court held, still in no. 17PA01909: “dans ces conditions et en admettant que les éléments relevés par le service étaient suffisants pour établir que M. B…avait en France un foyer d’habitation permanent, le requérant doit être regardé comme ayant eu au Royaume-Uni le centre de ses intérêts vitaux, quand bien même ses intérêts professionnels étaient situés en France”. Even assuming a permanent home in France, the centre of vital interests was in the United Kingdom, even though the professional interests were in France. The treaty therefore blocked French tax on worldwide income. The extra assessments for 2010 and 2011, and the penalties, were discharged.

That judgment is not a promise that a London flat plus a British partner will always win. It is a map of the evidence that moved the court: where the couple actually lived, where the child was born, the relative value of the homes, and the fact of dual filing. A retired couple whose daily life, doctors, clubs and family are in Charente, with a house in Surrey kept for visits, will usually have the centre of vital interests in France. A person who still sleeps most weeks in Britain, whose partner and school-age children are in Britain, and whose French house is a holiday property, may have the opposite result even if French law, looking at days or at a French bank account, would have claimed residence. The treaty does not ask which passport you hold until the last rung of the ladder.

If the treaty assigns you to the United Kingdom, France may still tax French-source income. Article 164 A of the Code général des impôts provides: “Les revenus de source française des personnes qui n’ont pas leur domicile fiscal en France sont déterminés selon les règles applicables aux revenus de même nature perçus par les personnes qui ont leur domicile fiscal en France. Toutefois, aucune des charges déductibles du revenu global en application des dispositions du présent code ne peut être déduite.” French-source income of a non-resident is computed under the same heading rules as for a resident, but personal charges against total income are not deducted. Article 164 B then lists what counts as French-source, starting with “a. Les revenus d’immeubles sis en France ou de droits relatifs à ces immeubles” (income from immovable property in France or rights in such property). A British non-resident who lets a French house remains taxable in France on that rent. The treaty, in article 6, gives the same result for immovable property. Residence under article 4 decides the rest of the map: pensions, UK interest, UK dividends, UK gains. Those topics are developed in the firm’s guides on UK savings, ISAs and bank accounts and on UK rental income of a French resident.

II. I have a French tax bill or a dual-residence letter: how do I declare and how do I challenge?

A. What France taxes once you are resident, and the returns you actually file

If, after the two-step analysis, you are a resident of France, article 4 A does what it says: France taxes the whole of your income. UK salary, UK pensions, UK dividends, UK interest, UK rental profits and UK capital gains enter the French return. The treaty then allocates taxing rights heading by heading and, where France may still tax, often gives a credit. In Conseil d’État, 9th and 10th chambers combined, 12 February 2020, no. 435907, a case on social charges and the Franco-British convention, the court quoted article 24 of the 19 June 2008 convention and held that the words “nonobstant toute autre disposition de la présente Convention” mean that even where other articles say income is taxable, or taxable only, in the United Kingdom, “ces revenus peuvent néanmoins être pris en compte pour le calcul de l’impôt français”. France may still put the income in the computation. The credit mechanism is what prevents double tax, not silence in the French return.

The annual income return is form 2042, with foreign income on form 2047 where required. UK bank accounts, ISAs included, must also be listed each year on form 3916, the foreign-account return; that duty and the 1,500 euro fine for an omission are explained in the savings guide already cited. A French resident who owns UK or French property above the wealth-tax threshold faces a separate return under the impôt sur la fortune immobilière (real-estate wealth tax), described in the firm’s note on IFI bills for British owners. None of those forms is optional once residence is established. HMRC self-assessment does not replace them.

If you file nothing, the administration is not powerless. Article L. 66 of the Livre des procédures fiscales (the tax procedures book) provides: “Sont taxés d’office : 1° à l’impôt sur le revenu, les contribuables qui n’ont pas déposé dans le délai légal la déclaration d’ensemble de leurs revenus” — taxpayers who have not filed the overall income return (déclaration d’ensemble) in time are assessed of the administration’s own motion, subject to a regularisation procedure. The charge then comes with surcharges. Article 1728 of the Code général des impôts, in force in its current wording since 21 February 2026, states: “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 : a. 10 % en l’absence de mise en demeure ou en cas de dépôt de la déclaration ou de l’acte dans les trente jours suivant la réception d’une mise en demeure d’avoir à le produire dans ce délai ; b. 40 % lorsque la déclaration ou l’acte n’a pas été déposé dans les trente jours suivant la réception d’une mise en demeure d’avoir à le produire dans ce délai ; c. 80 % en cas de découverte d’une activité occulte”. Ten per cent if you file late without a formal notice, or within thirty days of that notice; forty per cent if you still have not filed thirty days after the notice; eighty per cent if a concealed activity is discovered. Late-payment interest under article 1727 of the same code, still in force until 1 January 2027, is due as well: “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.”

A British person who has just moved, or who still thinks the 90/180 Schengen clock is the same thing as tax residence, often discovers this machinery only when a proposition de rectification (a proposed reassessment) arrives. That letter is not yet the tax. It is the administration’s reasoned view, with a time limit to reply. The file you build at that stage is the same file the court will later read: travel, family, homes, utilities, school, work, bank flows, and the UK returns. If you agree that you are French-resident, the useful work is to put every foreign item on the return and to claim the treaty credit, not to argue days. If you dispute residence, the useful work is to answer the proposal in time, with documents, rather than to ignore it.

Arrival and departure years are split years in UK practice more often than in French practice. France generally looks at the calendar year and at the tests in article 4 B for that year. A mid-year move can therefore produce a year in which HMRC treats you as UK-resident for part of the year and France treats you as resident for the whole year, or the reverse. The treaty tie-breaker is applied to the dual-resident period. It does not rewrite either domestic statute. The practical answer is to file in both States for that year, attach a short residence note, and claim the credit or the exemption the convention actually gives, heading by heading, instead of assuming that one return cancels the other.

B. How to challenge a residence assessment, a surcharge or a dual claim

The claim against a French income-tax assessment is a réclamation contentieuse, a formal contentious claim to the tax administration. Article L. 190 of the Livre des procédures fiscales, still in force until 1 January 2027, opens with: “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.” A claim that the administration got residence wrong, or that the treaty blocks worldwide tax, is exactly that: the benefit of a statutory and treaty right, and the correction of an error in the base of the tax.

The time limit is in article R*196-1 of the same book, in the version in force since 30 July 2026: “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 ordinary language, 31 December of the second year after the year of the collection roll or of the collection notice, or after the year of payment if there was no roll, or after the year of the event that founds the claim. A 2024 assessment notified in 2025 is typically open until 31 December 2027. Missing that date is fatal to the claim, however strong the treaty argument.

If the administration rejects the claim, or does not give full satisfaction, the next step for income tax is the administrative court. Article L. 199 of the Livre des procédures fiscales, in force until 1 January 2027, states: “En matière d’impôts directs et de taxes sur le chiffre d’affaires ou de taxes assimilées, les décisions rendues par l’administration sur les réclamations contentieuses et qui ne donnent pas entière satisfaction aux intéressés peuvent être portées devant le tribunal administratif.” Wealth tax, registration duties and similar charges go to the judicial court, not the administrative court. Residence for income tax is an administrative-court case. In Paris and Île-de-France, a taxpayer whose tax file is handled in Paris brings the action before the Tribunal administratif de Paris, with appeal to the Cour administrative d’appel de Paris. The 2018 film-maker judgment already cited was notified in copy to the Direction de contrôle fiscal Île-de-France. A person who claims to be a non-resident is often managed by the Direction des impôts des non-résidents rather than by a local service. The claim still follows article R*196-1. The court still follows the two-step: French law, then the convention.

What the claim must contain is not a speech about Brexit. It is a chronology of the year, the tests in article 4 B taken one by one, the documents for each test, and then, if dual residence is made out, the rungs of article 4 of the convention with the same documents. A day-count spreadsheet without a family story will lose against a foyer, as in the 2023 Paris case. A French bank account and a French SCI without the London household story will lose the treaty, as the film-maker would have done if the court had stopped at point 3. The winning combination in that case was to accept, for the sake of argument, a French permanent home and still prove that the centre of vital interests was in Britain. The losing combination in the 2023 case was to count 201 days abroad and ignore the Paris flat, the employee and the utility bills.

HMRC has its own machinery: the statutory residence test, split-year treatment, and, if both States persist, the mutual agreement procedure under the convention. A British reader should not wait for Paris and London to write to each other before filing the French claim. The French time limit in article R*196-1 runs whether or not a MAP request is open. Paying the tax to stop penalties, then claiming, is often safer than letting recovery run. A claim can ask for discharge of the tax and of the article 1728 surcharge. Deliberate-failure penalties, where they have been added, require a separate attack on the administration’s proof of intent. In the film-maker case the court discharged the extra tax and the penalties together once the treaty applied. That result followed from the residence finding, not from a free-standing plea on penalties.

None of this is a reason to hide a move. The cheaper path, if you have in fact made France your home, is to register, file form 2042, declare foreign accounts, and use the treaty credits. The cheaper path, if you have not, is to keep the French house as a second home, watch the Schengen 90/180 rule if you are a visitor, and be ready to prove that the foyer, the work and the money remain in Britain. The expensive path is the one this article is written for: a year in which both offices claim you, no return on one side, and a letter that has to be answered with the texts rather than with a myth about 183 days.

Conclusion

French tax residence after Brexit is not a day-count and it is not a visa. Article 4 A taxes worldwide income once article 4 B finds a foyer, a main stay, a principal activity or a centre of economic interests in France. The Conseil d’État has said that the main stay is only a fallback when there is no foyer. The Paris court of appeal has said that 201 days abroad do not move a Paris home, and that French-source income can fix an economic centre even where the work is filmed abroad. The same court has also shown that article 4 of the 19 June 2008 convention can still assign a dual resident to the United Kingdom where the centre of vital interests is there. The claim against a wrong assessment is a timed réclamation, then the administrative court. The file is family, houses, work and money, in that order, with the treaty last.

Need a quick opinion on your case

If you have received a French tax bill, a dual-residence letter from HMRC or the French tax office, or you need to know where you stand before you move, our firm offers a telephone consultation within 48 hours with a lawyer of the firm. Call +33 6 46 60 58 22 or write via our contact page. The firm advises clients in Paris and Île-de-France as well as British residents and second-home owners throughout France.