You live in France, your employment contract is governed by English law, your line manager sits in London, and your laptop sits on a desk in Lyon, Bordeaux or a farmhouse in the Dordogne. Since Brexit, this everyday arrangement has become one of the most legally tangled situations a British national in France can face. Your employer in Britain often assumes that because the contract is English and the salary is paid in pounds into a British bank account, nothing changes. The French authorities take the opposite view: work performed on French soil brings French social security, French tax residence rules and French immigration requirements into play, whether or not your employer has an office, a branch or even a single client in France. The UK’s withdrawal from the European Union removed the two cushions that used to soften this shock: free movement, which let British citizens live and work in France without a permit, and the EU social security coordination rules, which organised in a predictable way the position of people working across borders. This article explains, for a British employee working remotely from France for a UK employer, where social contributions are due and why the much-discussed A1 certificate does not solve the problem, how French tax residence and the France-UK double tax treaty allocate the right to tax your salary, which residence and work permits you need, what your employer must do in France, and how to challenge an URSSAF reassessment or an administrative refusal.

I. Your Salary Earned from France Falls Under French Social Security, Not British National Insurance

A. Working on French Soil Means Compulsory Affiliation to the French General Scheme

French social security law starts from a territorial principle: it is the place where the work is physically performed that decides which legislation applies, not the nationality of the employee, not the law governing the contract, and not the country where the employer is established. Article L. 311-2 of the Social Security Code provides that the following are compulsorily affiliated to the social insurance of the general scheme, whatever their age and even if they hold a pension: “toutes les personnes quelle que soit leur nationalité, de l’un ou de l’autre sexe, salariées ou travaillant à quelque titre ou en quelque lieu que ce soit, pour un ou plusieurs employeurs et quels que soient le montant et la nature de leur rémunération, la forme, la nature ou la validité de leur contrat ou la nature de leur statut.” A British citizen working from home in France for a London company falls squarely within this text: a salaried person, working in whatever place, for an employer, whatever the form of the contract. The Cour de cassation applies the same logic at the general level of the Code. In its judgment of 20 March 2025, the Second Civil Chamber recalled, on the basis of article L. 111-2-2 of the Social Security Code, that: “toute personne exerçant une activité salariée ou non sur le territoire français est obligatoirement affiliée au régime obligatoire de sécurité sociale français, sous réserve des traités et accords internationaux” (Cass. 2e civ., 20 March 2025, No. 23-12.264). That reservation for treaties and international agreements matters, and it will be examined below, but for a British remote worker it offers no escape: since Brexit there is no EU coordination regulation between France and the United Kingdom that would keep a person working permanently in France under British National Insurance, and the bilateral social security instruments that exist do not cover this situation.

The practical consequence is that the UK employer must treat the French-based employee as subject to French contributions. The employer has to register as an employer in France with URSSAF, the French body that collects social security contributions (Unions de recouvrement des cotisations de sécurité sociale et d’allocations familiales), declare the employee, and pay the French employer and employee contributions on the salary. This obligation exists even though the employer has no establishment (no office, branch or subsidiary) in France: article L. 111-2-2 expressly covers activity performed in France “pour le compte d’un ou de plusieurs employeurs, ayant ou non un établissement en France” (for one or more employers, whether or not they have an establishment in France). The hiring formalities follow: article L. 1221-10 of the Labour Code states that: “L’embauche d’un salarié ne peut intervenir qu’après déclaration nominative accomplie par l’employeur auprès des organismes de protection sociale désignés à cet effet.” In practice this is the DPAE, the prior declaration of hiring (déclaration préalable à l’embauche), which the UK employer, or a representative it appoints in France, must complete before the employee starts working from France. Payslips must then reflect French law: French minimum wage rules, French working time limits, paid leave accrual and the contributions that fund health insurance, pensions, family benefits, unemployment insurance and workplace accident cover. An employer that keeps the employee on a purely British payroll, deducting only British National Insurance while the employee lives and works full-time in France, accumulates contribution arrears on the French side and exposes itself to a reassessment (redressement) with surcharges, as well as potential criminal exposure for concealed work if the French employment was deliberately hidden.

Employees sometimes ask whether they can simply remain affiliated in Britain voluntarily and ignore France. The answer is no for the compulsory schemes: French affiliation is a matter of public policy and cannot be waived by contract. What remains possible is complementary: a British employee working in France may keep voluntary top-up cover, for example with the Caisse des Français de l’étranger for certain risks, but that never replaces the compulsory French affiliation for work performed in France. The Cour de cassation made the boundary clear in a case about employees sent abroad: voluntary insurance with the Caisse des Français de l’étranger is a faculty, whereas compulsory affiliation follows the legislation designated by the applicable rules (Cass. 2e civ., 13 October 2022, No. 21-13.252). The mirror applies in the other direction: no private arrangement, no English-law clause and no British payroll can displace the compulsory French scheme for work physically done in France.

B. Secondment (Détachement) and the A1 Certificate Do Not Cover a Permanent Remote Posting in France

Many UK employers believe that an A1 certificate, the document that proves an employee remains covered by their home social security system while working temporarily in another state, solves the problem. It does not, because remote work from France is not secondment (détachement). Under article L. 1262-1 of the Labour Code, an employer established outside France may only second employees to French territory temporarily, “à condition qu’il existe un contrat de travail entre cet employeur et le salarié et que leur relation de travail subsiste pendant la période de détachement”, and the secondment must fit one of three defined cases: performance of a service contract with a French recipient, movement between establishments of the same business or group, or work on the employer’s own account without a French recipient. A British employee who has settled in France and works from home there on a lasting basis fits none of these temporary patterns comfortably, and certainly not a permanent relocation dressed up as an open-ended secondment. Before Brexit, short temporary postings from the UK to France could rely on EU coordination and the A1; after Brexit, the EU regulations no longer bind the United Kingdom for new situations, and France-UK arrangements do not recreate a general right to keep a permanently France-based worker under British National Insurance.

The case law confirms how strictly the courts police the boundary of secondment. In the 20 March 2025 judgment already cited, the Cour de cassation set out the mechanism of the France-Japan social security agreement, which works on the same model as most bilateral instruments: first, “toute personne, susceptible d’être affiliée à titre obligatoire conformément à la législation des deux États contractants, qui exerce une activité salariée ou non salariée dans l’un des États contractants, est soumise uniquement à la législation de cet État contractant, au titre de cette activité, sauf dispositions contraires” (the state-of-work rule), and second, the secondment exception applies only where the employee is genuinely sent by an employer established in one state to work for that employer in the other state for a foreseeable period not exceeding five years (Cass. 2e civ., 20 March 2025, No. 23-12.264). Transposed to a British remote worker, the lesson is direct: the state-of-work rule designates France, and the secondment exception requires a genuine temporary posting with a maintained link of subordination to the sending employer, not a personal decision to live in France while keeping a British job. The complementary judgment of 13 October 2022 reinforces the point from the French domestic side: workers temporarily sent abroad by their employer remain under French legislation only “à la condition que l’employeur s’engage à s’acquitter de l’intégralité des cotisations dues auprès de la caisse d’affiliation du salarié”, and beyond that framework, cover abroad is a voluntary faculty, not compulsory affiliation (Cass. 2e civ., 13 October 2022, No. 21-13.252). In short, an A1 or equivalent certificate presupposes a temporary posting that a permanent remote arrangement cannot credibly claim, and presenting an inapplicable certificate does not protect either the employer or the employee when URSSAF inspects.

Some employers try a different route: engaging the France-based worker as an independent contractor or through an umbrella or portage company to avoid French employer registration. This changes the legal analysis without removing the risk. Reclassification as an employee remains possible wherever the facts show subordination, and the contributions then fall due with penalties. Genuine self-employment, by contrast, brings its own French affiliation for the self-employed and its own registration duties. Either way, the physical performance of the work in France is the trigger, and paperwork drafted in London does not move the place of work. The only compliant structures are to register as a foreign employer in France and run a French payroll, to use a properly constituted employer of record or French subsidiary that genuinely employs the worker, or in some cases to transfer the contract to a French entity of the group. Each option has costs, and the cheapest short-term fix, doing nothing, is the one that produces the largest reassessment later.

II. Tax Residence, the Right to Stay and Work, and How to Fight a Bill or a Refusal

A. Living and Working in France Usually Makes You a French Tax Resident, and the Treaty Gives France the First Right to Tax the Salary

Social security and tax follow different rules, but for a British remote worker living full-time in France they usually point to the same country. Under article 4 B of the General Tax Code, a person is regarded as having their tax domicile (domicile fiscal) in France where they meet any one of three alternative tests: “a. Les personnes qui ont en France leur foyer ou le lieu de leur séjour principal” (their home or principal place of stay), “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” (those who carry on a professional activity in France, unless it is merely ancillary), or “c. Celles qui ont en France le centre de leurs intérêts économiques” (those whose centre of economic interests is in France). A British employee who rents or owns a home in France, whose family lives there, and who performs their salaried work there day after day will normally satisfy the first test alone, and often the second as well, since full-time remote work is the opposite of ancillary. The same article adds that these domestic tests yield to international double tax treaties: a person who meets a domestic test in France “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 treaty therefore has the last word where both states claim residence.

The applicable treaty is the France-United Kingdom convention of 19 June 2008 for the avoidance of double taxation, published in France by Decree No. 2010-20 of 7 January 2010. Its residence article provides that a person is a resident of a contracting state wherever domestic law makes that person liable to tax there by reason of domicile, residence, place of management or any similar criterion. Where an individual is resident in both states under paragraph 1, paragraph 2 resolves the conflict in stages, starting with the permanent home and, where each state can claim one, moving to the state with which personal and economic relations are closest (the centre of vital interests). Failing that, habitual abode, then nationality, then mutual agreement between the authorities decide. For a British remote worker whose permanent home, spouse, children and daily working life are all in France, with perhaps only visits to family in Britain, the tie-breaker normally confirms French residence, even if the person keeps a British passport, a British bank account and a house let out in the UK. The Cour de cassation insists on the correct method: first determine residence under each state’s domestic law, and only if both claim the person, apply the treaty’s paragraph 2 criteria to resolve the dual residence (Cass. com., 24 November 2021, No. 19-14.013). Skipping the first stage, or treating British nationality or a payslip in pounds as decisive, is an error of method that the courts sanction.

Once French residence is established, the treaty article on employment income allocates the taxing right. Under Article 14, paragraph 1, of the 2008 convention, salaries and similar pay received by a resident for salaried employment are taxable only in the state of residence unless the employment is exercised in the other state, in which case that other state may tax the corresponding pay. A French-resident employee whose work is performed in France is therefore taxable in France on the salary, regardless of the employer being British. The narrow exception in paragraph 2, which would let the residence state keep exclusive taxation where the employee stays in the other state for no more than 183 days in twelve months, the pay is borne by a non-resident employer and no permanent establishment bears the cost, cannot help a person who lives and works in France all year round: the 183-day condition fails on its face. Double taxation is then relieved in the other state by exemption or credit under the treaty’s relief article, so that tax paid in France on the employment income is taken into account in Britain, but the mechanism never makes the salary taxable only in Britain. In France, the salary must be declared through the annual income tax return, and the social charges flow through the French payroll; in Britain, the employee or the employer should regularise the PAYE and National Insurance position so that British deductions stop being operated as if the employee were still resident and working in Britain. Keeping silent on both sides is the worst option: the French tax administration can tax the undeclared salary with penalties, and HMRC may continue to treat the person as UK-resident until the statutory residence position is clarified.

Two related tax points deserve attention because they surprise British remote workers. First, the employer’s presence: if the UK company has no French establishment but the employee works habitually from France, the question of a French permanent establishment of the British enterprise can arise in some configurations, particularly where the employee concludes contracts on behalf of the employer. That is a separate analysis from the employee’s own residence and depends on the functions actually performed; it should be examined rather than assumed away. Second, pension contributions: the treaty contains a specific provision allowing contributions paid by an individual working in one state to a pension scheme established and recognised in the other state to be deducted in the state of work under the same conditions as domestic schemes, provided the person was not resident there and contributed before starting the work. A British employee who keeps paying into a UK pension while working from France should therefore verify whether the scheme qualifies and claim the deduction correctly rather than either ignoring the contributions or assuming they are automatically relieved.

B. Residence Permits, Employer Registration, and Challenging a Reassessment or a Refusal

Since the end of free movement, a British citizen who wants to live and work in France needs a legal basis for both stay and work, unless they already hold a Withdrawal Agreement residence document. The route depends on the situation, but the work-authorisation requirement is general. Article L. 5221-2 of the Labour Code provides that to enter France in order to carry on a salaried occupation, a foreign national must present: “1° Les documents et visas exigés par les conventions internationales et les règlements en vigueur ; 2° Un contrat de travail visé par l’autorité administrative ou une autorisation de travail.” For an employee already lawfully in France seeking a permit as an employee, article L. 421-1 of the Code on the Entry and Stay of Foreign Nationals (CESEDA) states that a foreign national working under an open-ended contract is issued a temporary residence card marked “salarié” for a maximum of one year, and that: “La délivrance de cette carte de séjour est subordonnée à la détention préalable d’une autorisation de travail, dans les conditions prévues par les articles L. 5221-2 et suivants du code du travail”. In practice, the UK employer must therefore obtain a work authorisation for the British employee before the “salarié” card can be issued, and the application must explain the arrangement honestly: a remote worker for a foreign employer with no French establishment is an unusual file, and presenting it as a standard local hiring invites questions. Depending on salary level, qualifications and the employer’s structure, other permits such as the multi-year “passeport talent” or an EU Blue Card route may fit better than the one-year “salarié” card, and self-employed status points to different permits altogether. The key point is that none of these routes is automatic, and working in France while holding only a short-stay visa or visa-freeentry, or while a permit application is merely contemplated, exposes the employee to a refusal of stay, an order to leave, and complications at renewal. Holders of a Withdrawal Agreement card are in a different and protected position, but that protection covers those who were already lawfully resident before the end of the transition period, not newcomers who arrived afterwards and simply kept a British job.

On the employer side, the compliance file has three layers: immigration (work authorisation where needed), labour law (declaration of hiring, French-law employment terms, health and safety duties for home working including the employer’s obligations around the home workspace), and social security (registration, monthly or quarterly declarations, payment). URSSAF, the collection body, monitors compliance through inspections (contrôles). Article L. 243-7 of the Social Security Code entrusts URSSAF’s agents with verifying employers’ application of the Code, and those agents, sworn and approved, are not bound by the label the inspected party puts on the facts: a “contractor agreement” or an “extended business trip” is re-examined for what it really is. Where the inspection finds missing contributions, URSSAF notifies a reassessment through a letter of observations, which the employer can answer, followed if maintained by formal recovery. At that formal stage, the employer’s best defence is often procedural before it is substantive, because French courts enforce strict discipline on recovery documents. Article L. 244-2 of the Social Security Code requires that any recovery action be preceded by a formal notice (mise en demeure) sent by registered letter or any means giving certain date of receipt, whose content “doit être précis et motivé, dans des conditions fixées par décret en Conseil d’Etat.” The Cour de cassation draws a sharp consequence: “la notification d’une mise en demeure régulière constitue un préalable obligatoire aux poursuites et que la nullité de la mise en demeure fait obstacle à ce que, dans la même instance, l’organisme de recouvrement poursuive le paiement des sommes qui en font l’objet” (Cass. 2e civ., 17 October 2024, No. 21-25.851). A vague, unmotivated or incorrectly calculated formal notice can therefore defeat the recovery in the pending proceedings, even where contributions appear due in principle. Employers facing a reassessment should have the letter of observations, the reply, the formal notice and any subsequent enforcement order (contrainte) checked line by line against the Code’s requirements, while also preparing the substantive arguments on affiliation, applicable legislation and calculation.

Refusals can also come from the prefecture (préfecture), the state authority that issues residence permits, or from the hiring-declaration and payroll side where a body declines to register an atypical employer. Every refusal must be read for what it actually decides, which legal basis it cites, and which remedy it indicates on the document itself: the time limits and competent court or tribunal are stated in the notification, and they vary with the decision, so they must be taken from the paper rather than assumed. The standard first step is usually an administrative appeal, either to the authority that decided (recours gracieux) or to its superior (recours hiérarchique), combined where timing requires with an appeal to the administrative court, if necessary under the urgent procedure where a removal order or a loss of the right to work is at stake. For contribution disputes, the challenge runs before the judicial courts, and the same discipline applies: identify precisely what is contested, meet the stated time limit, and preserve evidence of the actual place of work, the employer’s instructions, pay records and the certificates held. Across all these challenges, one evidentiary theme recurs: the authorities decide on facts, not labels. Dated proof of daily presence in France, the remote-work agreement, correspondence showing where instructions are received and executed, and complete payroll records weigh more than contractual recitals drafted in London.

Conclusion

A British citizen who works remotely from France for a UK employer lives under French social security for that work, is in most cases a French tax resident whose salary France may tax first under the 2008 treaty, and needs a proper residence and work-permit basis now that free movement has ended. The A1 certificate belongs to temporary secondment and does not cover a lasting remote posting; the English-law contract and the British payroll do not displace compulsory French affiliation; and the 183-day treaty exception does not rescue a person who lives and works in France all year. Employers should register in France, run compliant declarations and adapt the contract to French mandatory rules, while employees should declare the salary in France and regularise the British position. Where URSSAF reassesses or the prefecture refuses, the documents must be checked with rigour: a defective formal notice can defeat a recovery, and a misclassified residence file can be rebuilt on the correct permit route. Taken early, these steps cost far less than arrears, penalties and immigration trouble later.