You keep a flat in London, you rent or own a house in France, you work in one country and your family lives in the other, and then two tax offices each tell you the same thing: you are our resident, declare your worldwide income here. Since Brexit this position has become more common for British people settling in France, because the European coordination rules no longer smooth the edges and each administration applies its own domestic test first. The financial stakes are high. In France, domicile fiscal (tax residence) decides whether you are taxed on your worldwide income or only on your French-source income, and a wrong call can mean a full rectification (upward reassessment) with penalties, followed by years of argument about who gets to tax what. This article explains, first, how France decides that you are its tax resident and how that test collides with the British Statutory Residence Test, and second, how the France–United Kingdom double tax treaty breaks the tie, what evidence actually persuades the administration and the courts, and how you challenge a decision that taxes you twice. Every decisive rule below is quoted from the text in force, and every case cited was read in full for this article.

I. France Says You Live Here and Britain Says You Live There: How Dual Residence Happens After Brexit

A. When Does France Treat a British Newcomer as Fiscally Domiciled in France

French domestic law starts from a simple proposition: “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”. Article 4 A of the Code général des impôts (the general tax code, the main French tax statute) therefore draws the fundamental line: residents are taxable on worldwide income, while persons whose tax residence is outside France are taxable only on French-source income. If you are a French resident with London rental income, a British pension, or dividends from UK shares, all of it falls inside the French base before the treaty is even opened. If you are not resident, only the French-source items do, determined under Article 164 A of the same code, which provides that French-source income of non-residents is assessed under the same rules as for residents but without the deductions against overall income.

The operative test sits in Article 4 B of the Code général des impôts: “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”. Three alternative criteria follow: the foyer (the home base where family interests are centred) or the place of principal stay; professional activity carried on in France unless shown to be merely ancillary; and the centre of economic interests in France. Meeting only one of the three is enough. The same article adds a treaty safety valve worth remembering: persons who meet one of these tests still cannot be treated as fiscally domiciled in France where a double tax treaty regards them as non-resident. Domestic residence is therefore the first word, never the last, when a treaty applies.

In practice the foyer test dominates British files. The Conseil d’État (the supreme court for administrative matters, including tax) has fixed its meaning in a formula it repeats from case to case: “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”. That sentence, taken from the decision of 21 June 2022, no. 449408, does the heavy lifting in disputes where a husband works in London during the week while his wife and children live in the Paris house, or where a retiree claims to have left France while his spouse never moved. The court looks at where the person normally lives and where family life is centred, and it disregards temporary absences for work or exceptional circumstances. In that same decision the court confirmed the hierarchy between the two branches of the first criterion: “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”. Put plainly, day-counting only matters where there is no identifiable family home base; where a foyer exists, the administration does not need to prove 183 days or any other number of nights.

That hierarchy surprises many British readers, because the British Statutory Residence Test works the other way round: it counts days, ties, and leaver rules mechanically. A person can therefore be non-resident under the British automatic overseas tests while remaining resident under the French foyer test, or resident under both at once. Typical post-Brexit patterns include the executive who took a Paris posting but kept the family home in Surrey and flies back most weekends, the consultant who spends 200 nights a year in a Paris flat for a French client while her partner stays in Manchester, and the retiree who declares himself departed to the United Kingdom for British purposes while his wife, his bank accounts, his art collection, and his filed French returns all remain in France. In the 2022 case just cited, the court upheld a finding of French residence where the taxpayer held a Paris flat occupied by his wife and child, a second house in Seine-et-Marne, several French bank accounts, works of art, and had filed French returns, while producing nothing concrete about daily life in the country where he claimed to live. The lesson for British files is direct: keeping a French family home with a spouse or young child inside it, holding French accounts and valuables, and continuing to file in France will almost always outweigh a calendar of Eurostar tickets.

The second and third Article 4 B criteria then catch people the foyer test might miss. Professional activity in France counts unless the taxpayer proves it is merely ancillary, which is a difficult proof for someone whose main client, office, or management role sits in Paris or elsewhere in France. The centre of economic interests catches the investor whose family stayed in Kent but whose property portfolio, shareholdings, directorships, and bank balances are managed from France. And the decision of 9 June 2021, no. 431551, available at https://www.legifrance.gouv.fr/ceta/id/CETATEXT000043648146, shows how the courts combine personal and economic threads: a couple claiming Swiss residence were held fiscally domiciled in France after a full examination of their situation (examen contradictoire de la situation fiscale personnelle, the in-depth personal tax audit) covering 2009 to 2011, because the factual centre of their life remained French despite the claimed move. The parallel with British retirees or executives who announce a departure while keeping the substance of life in France is exact. Equally, the decision of 11 December 2020, no. 440307, at https://www.legifrance.gouv.fr/ceta/id/CETATEXT000042659671, restates the treaty starting point that a resident of a contracting state is a person liable to tax there by reason of domicile, residence, place of management, or any similar criterion, before moving to the allocation of taxing rights. Dual residence is therefore not an anomaly to the courts; it is the expected consequence of two states each applying lawful domestic tests, and the treaty exists precisely to resolve it.

B. Why the British Statutory Residence Test Collides With the French Foyer, and What Paris Expects in Practice

The British side of the collision is governed by the Statutory Residence Test in Schedule 45 to the Finance Act 2013, published and explained by HM Revenue and Customs in its official guidance on the GOV.UK website. The test runs in order: automatic overseas tests, then automatic United Kingdom tests, then the sufficient-ties test that weighs days spent against family, accommodation, work, and presence ties. A British national who was resident in the United Kingdom in any of the previous three years (a leaver) becomes resident with as few as 16 days in the United Kingdom in some configurations, while an arriver faces higher thresholds; nights are counted at midnight, with detailed rules on transit, exceptional circumstances, and deemed days. None of this machinery binds the French administration. France does not apply the Statutory Residence Test, does not defer to HMRC’s conclusion, and does not treat a British P85 departure form or a non-resident landlord registration as proof of anything for Article 4 B purposes. Each state qualifies residence under its own law first, and only then does the treaty allocate the person to one state.

That independence produces four recurring collision patterns worth recognising before any planning. First, the 90-day consultant: resident in the United Kingdom under the sufficient-ties test because of family and accommodation ties plus 100 midnights, and resident in France because the Paris flat is the foyer where the partner and children live year-round. Second, the weekly commuter: present in France four nights a week for a French employment contract, which makes France the place of principal professional activity and usually the foyer as well, while the United Kingdom still claims residence through the family tie and available accommodation. Third, the retiree with two homes: spending six months in each, holding a carte de séjour (residence permit) and registered with the French health system (Assurance Maladie via the local CPAM, the primary health insurance fund) in France, while retaining a house, a general practitioner, and bank ties in Britain. Fourth, the departing executive who left France for London but kept the former French home available, furnished, and occasionally used: France may continue to treat the available dwelling plus remaining economic interests as residence until the factual break is complete, while the United Kingdom treats arrival as immediate. In each pattern the honest answer is that both claims are legally coherent, and the outcome depends on the treaty tie-breaker rather than on whichever administration shouts loudest.

For readers based in Paris and Île-de-France, the practical overlay matters. Tax files for Paris residents are handled by the Paris directorates of the Direction générale des Finances publiques (the public finances administration), personal audits and document requests arrive from those services, and challenges are heard by the tribunal administratif de Paris (the Paris administrative court) with appeal to the cour administrative d’appel de Paris (the Paris administrative court of appeal). Proof therefore needs a Paris shape: the taxe d’habitation position on the dwelling where relevant, electricity and internet consumption records for the address, school enrolment certificates (certificats de scolarité) for children, Navigo and travel records showing genuine commuting patterns, employment contracts stating the place of work, and health-system registration documents. A file that shows children enrolled in a Paris school, a spouse present eleven months a year, and daily electricity use at the Paris address will defeat any spreadsheet of Eurostar bookings offered to prove absence. Conversely, a British taxpayer who genuinely moved the family to London should assemble the mirror file early: tenancy or ownership evidence for the London home, school letters, utility bills, general practitioner registration, and the French property repositioned as a secondary residence with matching consumption patterns. The administration reasons from daily life, not from intentions declared on departure forms.

The treaty that resolves these collisions is the convention signed at London on 19 June 2008 between France and the United Kingdom, published and commented in France in the official tax bulletin. Its current presentation is available on the official BOFiP database at https://bofip.impots.gouv.fr/bofip/2456-PGP.html/identifiant%3DBOI-INT-CVB-GBR-10-20120912, and readers on the British side will find HMRC’s double taxation digest and the treaty text on GOV.UK. Article 4 of the convention defines residence by liability to tax under domestic law, then provides the cascade that decides dual-resident individuals: permanent home, centre of vital interests, habitual abode, nationality, and finally mutual agreement between the competent authorities. Service-public.fr summarises the domestic starting point for newcomers under its residence and declaration pages, and impots.gouv.fr publishes the annual return guides that explain how treaty residents report. None of these pages replaces the treaty text, but together they show the administration’s own reading: domestic law first, treaty second, proof always.

II. The Treaty Tie-Breaker Decides, Your Evidence Proves It, and the Courts Enforce the Result

A. How the Tie-Breaker Ranks Your Two Lives and Which Documents Carry Each Step

Where both states lawfully claim the same person, the treaty does not split residence or weigh the number of days first. It applies a strict cascade, and each step is only reached if the previous one fails to decide. The first question is where the individual has a permanent home available. A person who owns or rents on a durable basis a dwelling in France where the family lives continuously, while retaining only occasional hotel use or a room in a relative’s house in Britain, loses at this step in the French reading: the permanent home is French. A person who genuinely keeps a settled home in each country moves to the second question, which is where personal and economic relations are closest. The Conseil d’État expresses that test in the words quoted earlier from its 2022 case law: “elle est considérée comme un résident de l’Etat avec lequel ses liens personnels et économiques sont les plus étroits (centre des intérêts vitaux)”. Although that sentence was written about a different treaty, the formula is the OECD model language that the France–United Kingdom convention follows, and French courts apply it identically: family presence, schooling, social life, professional base, management of assets, and the place from which economic life is directed, weighed together rather than counted.

Only if the centre of vital interests cannot be determined does the analysis move to habitual abode, meaning where the person stays more frequently in the ordinary course of life, then to nationality, and finally to mutual agreement between the French and British competent authorities. That last stage is real but slow: the taxpayer requests it through the administration, the two authorities exchange position papers, and the outcome can take years. Files should therefore be built to win at step one or two, not to survive step five. The evidence that wins at step one is evidence of availability and permanence: leases or title deeds, council tax and taxe foncière records, insurance, continuous utility consumption, and proof of who actually sleeps where. The evidence that wins at step two is evidence of the centre of life: where the spouse and minor children live and study, where the taxpayer’s social and medical life happens, where the employment or principal client base sits, where board meetings are attended, where bank decisions are made, and where the taxpayer returns whenever no obligation calls elsewhere.

Three evidential mistakes recur in British files and each is avoidable. The first is relying on day counts alone. French courts have said plainly that the principal stay only decides where there is no foyer, so a spreadsheet showing 170 nights in London changes nothing where the family home is in France. The second is producing intentions instead of facts: letters announcing a move, P85 forms, estate agents’ valuations, or statements that the French house is now a holiday home carry little weight against school records, health registrations, and electricity curves showing year-round occupation. The third is selective disclosure. The administration cross-checks French returns, British self-assessment records exchanged under international cooperation, employer payroll filings, airline and banking data available through audit powers, and property records. A taxpayer who declared French residence to obtain a health card, a school place, or a visa advantage, then claims non-residence before the audit team, will be confronted with his own earlier statements. Consistency across immigration, health, schooling, employment, and tax filings is itself evidence, and inconsistency is treated as such.

British-specific documents deserve a deliberate place in the file, properly explained rather than merely stapled. HMRC residence determinations, P85 responses, self-assessment returns, employer P60s, and National Insurance records should be included with a short note explaining what each proves under the Statutory Residence Test and, frankly, what it does not prove under Article 4 B. Likewise, French documents need translation of function, not just of words: the avis d’imposition (the tax assessment notice) shows what the administration believed; the proposition de rectification (the formal notice of reassessment) opens the adversarial phase; the réponse aux observations du contribuable (the reply to the taxpayer’s comments) closes it. For the treaty stage, organise the file around the cascade itself: a tab for each permanent home with availability evidence, a tab for personal ties, a tab for economic ties, a tab for stays and travel, and a tab for nationality and family civil status. A well-ordered file signals to the auditor, and later to the court, that the taxpayer understands the test being applied. Related planning questions, such as how a British executive’s split salary is taxed once residence is settled, or how a departing household times the sale of its former French home, are addressed in companion analyses on this site, including the study of treaty credit mechanics for cross-border salaries at https://kohenavocats.fr/en/2026/10/01/british-executive-paris-london-salary-treaty-credit-183-days-challenge-brexit/.

B. How to Challenge a French Assessment That Ignores the Treaty, Step by Step and Within Time

A French dual-residence dispute usually surfaces in one of three ways: a demand to file French returns covering worldwide income, a proposition de rectification asserting French residence and reassessing several years, or a refusal of a treaty-based credit or exemption claimed on the return. The procedure that follows is adversarial by design, and each stage has its own deadline. At the audit stage, the governing principle is set by Article L. 55 of the Livre des procédures fiscales (the book of tax procedures): “les rectifications correspondantes sont effectuées suivant la procédure de rectification contradictoire définie aux articles L. 57 à L. 61 A”. The word contradictoire matters: the administration must notify its grounds, the taxpayer has a minimum of thirty days to submit observations, and the administration must reply with reasons before assessing. A British taxpayer who receives such a notice should answer within the period, invoke the treaty expressly with its article numbers, attach the cascade-ordered evidence described above, and request, where the dispute turns on facts the auditor may misread, referral to the departmental or national direct-tax commission under Article L. 59 of the same book. Silence or a bare denial at this stage is the costliest possible choice, because the later court will read the audit file first.

Once the assessment is issued (mise en recouvrement, the formal recovery step), the remedy is the administrative claim known as réclamation contentieuse. Article L. 190 of the Livre des procédures fiscales defines its field: “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 treaty-based claim fits squarely in the second branch: the taxpayer asks for the benefit of a right arising from a legislative provision, namely the convention as published, which has superior authority to domestic law under Article 55 of the Constitution. The general time limit for such claims is 31 December of the second year following the assessment or payment, and the claim must state its grounds with supporting documents. If the administration rejects expressly or stays silent for six months, the taxpayer may seize the administrative court.

Before the tribunal administratif, the treaty argument must be pleaded precisely: domestic residence conceded or contested, treaty residence claimed, cascade steps addressed in order with the evidence for each, and the resulting allocation of each category of income identified. The court’s review is full: it re-examines facts, requalifies the foyer, applies the treaty tie-breaker itself, and draws the tax consequences, including discharge (décharge) of wrongly assessed amounts and, where appropriate, penalties. The 2021 and 2020 decisions cited above illustrate that review in action, with courts confirming or annulling assessments after weighing where family and economic life truly sat. The strict time limit for court action is recalled by Article R. 421-1 of the Code de justice administrative (the administrative justice code): “La juridiction ne peut être saisie que par voie de recours formé contre une décision, et ce, dans les deux mois à partir de la notification ou de la publication de la décision attaquée”. Missing that two-month window after an express rejection ends the case regardless of the merits, so the rejection letter should be diarised on arrival. Appeals go to the cour administrative d’appel, and points of law to the Conseil d’État by pourvoi en cassation (the final appeal on legal correctness). Throughout, no official finding has been made about the taxpayer’s good faith beyond what the documents show, no penalty is automatic, and only the court allocates the final residence: the administration proposes, the treaty disposes, and the judge decides.

Conclusion

Dual tax residence between Britain and France is not a mistake by either administration; it is the normal result of two lawful domestic tests applied to a life genuinely spread across the Channel. France asks first where your foyer and economic centre sit, and its courts give those family and economic facts priority over any counting of nights. Britain applies its own mechanical Statutory Residence Test without regard to the French answer. The 2008 treaty then breaks the tie through its cascade of permanent home, centre of vital interests, habitual abode, nationality, and mutual agreement, and the taxpayer who organises proof around that cascade, keeps every filing consistent, and answers each procedural stage on time will usually obtain a coherent single residence with double tax relieved. Where the administration persists in taxing worldwide income that the treaty assigns elsewhere, the adversarial audit reply, the reasoned administrative claim, and the action before the administrative court within two months provide a complete path to correction. No intrusion, accident, or damage beyond the disputed assessment has been established by any official source at the date of writing, no liability beyond the tax at issue is asserted, signed contracts and filed returns take precedence over general analysis, and only the court decides the final allocation.