You sold up in Manchester, signed the compromis in the Dordogne, and finally moved your family, your dog and your bank accounts to France. Then, in the spring after your arrival, a neighbour mentions the déclaration des revenus (the annual income tax return), and the calm evaporates: which country taxes your salary for the months before the move, where do your British dividends go, must you really list every current account you ever opened in the United Kingdom, and what happens to the tax you already paid to HM Revenue and Customs? This guide answers those questions in the order a British newcomer meets them. It explains every French term the first time it appears, links each decisive statement to its official text, and shows how the courts apply the rules to people in your position. Part I fixes the starting point: the day France starts taxing your worldwide income, and which form each kind of income belongs on. Part II deals with the two traps that cost newcomers the most money: undeclared British accounts and British tax left unrelieved in France. A paper return, three annexes, one treaty credit and two recent court rulings are all you need to understand before you file.

I. Your Arrival Year in the French Tax Net: Domicile, Worldwide Income and the Treaty Safety Net

A. The Day France Starts Taxing Your Worldwide Income: Domicile, Arrival Dates and the Treaty Tie-Breaker

France taxes its tax residents on their worldwide income from the day they become resident, not from the following 6 April and not from the next calendar year. The test is the domicile fiscal (the tax domicile), defined by Article 4 B of the General Tax Code (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 ; 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”. In plain English, you are treated as fiscally domiciled in France if your foyer (your home and the centre of your family interests) is in France, if France is the place of your main stay, or if you carry on a professional activity here otherwise than on a merely secondary basis. Meeting any one of these three criteria is enough, and the administration looks at the facts as they stand on the ground: where your spouse and children actually live, where you sleep most nights, and where you work day to day.

The leading court definition of the foyer comes from the Cour de cassation (France’s supreme court for civil and criminal matters), in a published ruling that still governs tax residence disputes: Court of Cassation, Commercial Chamber, 15 October 1996, appeal no. 94-19.120, where the court held that “le foyer du contribuable, qui détermine le domicile fiscal, s’entend du lieu où l’intéressé habite normalement et a le centre de ses intérêts familiaux, sans qu’il soit tenu compte de séjours effectués temporairement ailleurs, en raison notamment des nécessités de sa profession”. The taxpayer’s home, which determines the tax domicile, means the place where the person normally lives and keeps the centre of family interests, with no account taken of stays made temporarily elsewhere, particularly for professional reasons. For a British family that has bought its main house in France, enrolled the children in a French school and kept only a small flat in London for occasional trips, that formula points to France from the moving date, even if one spouse still commutes to the City two days a week. Conversely, keeping your family home in Kent while you rent a studio in Paris for a nine-month contract points the other way, because temporary professional presence does not move the foyer.

Income received before the move stays outside the French return; everything received on or after the day your domicile shifts to France falls inside it. Your April salary earned while still living in Leeds is a matter for HMRC alone, while your October salary earned living in Lyon belongs on the French return even if your British employer paid it into your old Halifax account in pounds. Where both countries claim you for the same period, the 2008 double tax treaty decides. The treaty, published in France by Decree no. 2010-20 of 7 January 2010 for the convention signed in London on 19 June 2008, and available in English on the GOV.UK treaty page, settles dual residence with a cascade that looks first at bricks and mortar: a person is treated as resident only of the State where a permanent home is available, and a home in both States sends the question to the State of closer personal and economic relations, then to habitual presence and nationality. A permanent home in both countries leads to the centre of vital interests, then to habitual presence, then to nationality. Newcomers who want the full mechanics of that cascade, with the evidence the administration expects, should read our companion guide to dual tax residence and the treaty tie-breaker before deciding which country eliminates the double charge and how.

The British side of the same move works differently, and the contrast explains many double-tax scares. The United Kingdom taxes by tax year running from 6 April to the following 5 April, and leavers may qualify for split-year treatment so that only the United Kingdom part of the year is charged as a resident, a mechanism summarised on GOV.UK. France has no split tax year: once your domicile moves to France in October, France taxes the worldwide income you receive from October to December, while HMRC may still treat you as United Kingdom resident for the whole year or grant split-year treatment depending on your circumstances. The treaty then allocates each item and grants the credit described in Part II, but the two systems never mirror each other, which is why keeping a month-by-month schedule of receipts, with the country of source and the date of payment for each, matters more in the arrival year than in any other. Where the two administrations genuinely overlap on the same income for the same period, the mutual-agreement procedure between the tax authorities exists as a last resort, but it moves slowly and demands the same complete file a court would require.

B. Which Income Goes on Which Form: the 2042, the 2047 and the Income France Taxes Only for the Rate

The filing duty itself is stated without ambiguity in Article 170 of the General Tax Code: “En vue de l’établissement de l’impôt sur le revenu, toute personne imposable audit impôt est tenue de souscrire et de faire parvenir à l’administration une déclaration détaillée de ses revenus et bénéfices, de ses charges de famille et des autres éléments nécessaires au calcul de l’impôt sur le revenu”. Every person liable to income tax must send the administration a detailed return of income and profits, family circumstances and the other elements needed to compute the tax. For a newcomer that return is built from three documents. The déclaration n° 2042 (the main return) carries your worldwide position: French and foreign wages, pensions, property income and family details. The déclaration n° 2047 (the foreign-income annex) details each item of income received from abroad, country by country, with the foreign tax paid, so the office can work out the treaty relief. The déclaration n° 2042-C (the complementary return) collects specific additional items such as certain capital gains, stock-option gains and income taxed at flat rates. The official filing guide on service-public.fr confirms the architecture and points first-time filers to the downloadable forms, since newcomers without an online account start on paper, a point developed in Part II below.

Four features of the French return surprise British filers, and each has a precise legal source. First, foreign dividends, interest and similar distributions fall inside French taxable income by statute: Article 120 of the General Tax Code provides that “Sont considérés comme revenus au sens du présent article : 1° Les dividendes, intérêts, arrérages et tous autres produits des actions de toute nature et des parts de fondateur des sociétés, compagnies ou entreprises financières, industrielles, commerciales, civiles et généralement quelconques dont le siège social est situé à l’étranger quelle que soit l’époque de leur création”. Dividends, interest and arrears from companies whose registered office sits abroad are income for French purposes. Your Lloyds dividends, your NS&I interest and the distributions from your stocks-and-shares ISA therefore enter the return. Note the ISA trap in particular: the British tax wrapper has no equivalent in French law, so interest and dividends sheltered from HMRC inside an ISA remain fully taxable in France once you are resident, and they must appear on the 2047 with the British tax shown as nil.

Second, income that the treaty assigns exclusively to the United Kingdom must still be written on the French return. Article 170, paragraph 4, of the General Tax Code states: “Le contribuable est tenu de déclarer les éléments du revenu global qui, en vertu d’une disposition du présent code ou d’une convention internationale relative aux doubles impositions ou d’un autre accord international, sont exonérés mais qui doivent être pris en compte pour le calcul de l’impôt applicable aux autres éléments du revenu global.” Exempt elements must be declared where they count towards the tax computed on the rest of the overall income. This is the taux effectif (effective-rate) method: France forgoes tax on the British-only item but uses it to push your remaining French-taxed income up the progressive scale. A newcomer who leaves a British-tax-only pension or certain government-service income off the return, thinking exempt means invisible, files an incomplete return and loses the argument before it starts.

Third, arriving mid-year does not give you two part-year returns. France works by foyer fiscal (tax household) for the calendar year: one return covering the whole year, with foreign-source income received before the move excluded and everything received afterwards included worldwide. Keep dated proof of the move, such as the inventory of delivery, the first electricity bill and the children’s school certificates, because the office routinely asks when the domicile shifted when a return mixes six months of Leeds wages with six months of Lyon wages. Fourth, rental income from a property you kept in Britain follows its own annex logic and its own treaty mechanics, with the 2047 carrying the net rent and the credit computed separately; the worked example for landlords is set out in our guide to British landlords declaring United Kingdom rental income in France, and the parallel treatment of lump sums and government pensions appears in our guide to British pensions taxed in France. Read those pages alongside this one rather than guessing which box your letting income or your 25 per cent lump sum belongs in.

II. British Accounts, the Treaty Credit and Setting a Wrong Bill Straight

A. Every British Account on Form 3916: the Dormant HSBC Lesson, Sixty-Day Demands and Fines Per Account

The déclaration n° 3916 (the foreign-account statement) is the annex newcomers most often overlook and the one the administration pursues most energetically. Article 1649 A, second paragraph, of the General Tax Code imposes the duty in these terms: “Les personnes physiques, les associations, les sociétés n’ayant pas la forme commerciale, domiciliées ou établies en France, sont tenues de déclarer, en même temps que leur déclaration de revenus ou de résultats, les références des comptes ouverts, détenus, utilisés ou clos à l’étranger.” Individuals domiciled or established in France must declare, together with their income return, the details of accounts opened, held, used or closed abroad. The four words are cumulative, not alternative: an account closed during the year must be declared exactly like an account still open, and an account you merely hold is declarable even if you never touched it. Every joint account counts for each holder, so a couple holding three Halifax accounts files three declarations each, and business accounts used for a self-employed activity are declarable alongside strictly private ones.

The dormant-account excuse was tested in court this year, in proceedings that began, in the court’s own words, “A la suite d’informations reçues des autorités fiscales du Royaume-Uni”. In Versailles Judicial Court, First Chamber, judgment of 7 May 2026, case no. 23/07001, a British-born resident of the Yvelines asked the court to cancel a reassessment of nearly 110,000 euros built on an undisclosed joint HSBC account in Britain, arguing that the account had been inactive, with no credit or debit movement apart from interest and bank charges, and that later corrected returns filed in her husband’s name cured the omission. The court set out the rule it applied from the provisions then in force: “La déclaration de compte mentionnée au II porte sur le ou les comptes ouverts, utilisés ou clos, au cours de l’année ou de l’exercice par le déclarant, l’un des membres de son foyer fiscal ou une personne rattachée à ce foyer.” The account declaration covers accounts opened, used or closed during the year by the filer, a member of the tax household or an attached person. It added the decisive precision: “Un compte est réputé avoir été utilisé par l’une des personnes visées au premier alinéa dès lors que celle-ci a effectué au moins une opération de crédit ou de débit pendant la période visée par la déclaration”. An account counts as used once a single credit or debit passes through it in the relevant period. Interest credited to the account is itself a credit movement, so the classic I left it dormant with only interest argument fails on its own terms.

The Versailles judgment of 7 May 2026 then rejected both defences in reasoning every British newcomer should memorise. On the scope of the duty, the court held that “tous les comptes désormais détenus à l’étranger étaient à déclarer à compter du 1er janvier 2019 au titre des années 2018 et suivantes”, all accounts held abroad being declarable from 1 January 2019 for 2018 onwards under the law of 23 October 2018, while noting that a transfer of 365,100 euros in January 2018 had in any event moved the account. On the attempted cure, it ruled that “Les déclarations rectificatives qu’elle verse aux débats, mentionnant pour déclarant son époux et pour des périodes postérieures, ne sont pas de nature à pallier cette carence”, corrected returns naming the husband as filer for later periods could not make good the shortfall. The outcome followed: the court dismissed the claim in full and ordered the claimant to bear the costs. Three practical lessons emerge. First, declare every British account from your first French return, including ISAs, premium bonds held through an account, joint accounts, accounts you consider empty and accounts closed during the year. Second, file each 3916 in your own name for the exact year concerned, because a spouse’s later return does not repair your omission. Third, expect the office to know already: routine exchanges of bank data between HMRC and the French administration mean an undisclosed Leeds or London account surfaces without any audit of your French affairs.

The sanctions make prevention far cheaper than cure. Article 1736, section IV, of the General Tax Code provides: “Les infractions aux dispositions du deuxième alinéa de l’article 1649 A et de l’article 1649 A bis sont passibles d’une amende de 1 500 € par compte ou avance non déclaré.” Breaches of the foreign-account duty carry a fine of 1,500 euros per undeclared account. Three forgotten accounts therefore cost 4,500 euros before any tax, interest or other penalty is added, and the fine applies per account and per year concerned. Beyond the fine, an omission exposes you to a targeted information procedure: Article L. 23 C of the Tax Procedure Book (Livre des procédures fiscales) allows the office, where the declaration duty has been missed at least once in the previous ten years, to act without opening a full personal tax examination, since “l’administration peut demander, indépendamment d’une procédure d’examen de situation fiscale personnelle, à la personne physique soumise à cette obligation de fournir dans un délai de soixante jours toutes informations ou justifications sur l’origine et les modalités d’acquisition des avoirs figurant sur le compte ou le contrat de capitalisation ou le placement de même nature”. The administration may demand within sixty days full information and supporting documents on the origin of the funds. A vague or late reply leads to a formal demand to complete, and then to taxation of the unexplained sums as income. Newcomers should therefore arrive at the first filing with a complete inventory: every sort code and account number, opening and closing dates, year-end statements, and the paper trail for any large transfer made around the move.

B. Paying Tax Once, Not Twice: the Treaty Credit, Social Charges and How to Challenge the Assessment

Declaring worldwide income does not mean paying tax twice on it. For a French resident with income taxable in the United Kingdom, the treaty grants France-side relief as a credit, not as an exemption, and the wording repays close reading. Article 24 of the 2008 convention grants the French resident a credit against French tax equal, for most income, to the slice of French tax attributable to that income, on condition that British tax was actually charged on it. The credit therefore equals the slice of French tax attributable to that income, granted on condition that British tax was actually charged on it. In practice the office computes French tax on your worldwide income including the British item, isolates the fraction corresponding to that item, compares it with the British tax proved by your P60, dividend vouchers, self-assessment statements and payment receipts, and grants the lower of the two. Where the British effective rate on that slice exceeds the French rate, the excess British tax remains unrelieved in France and only a claim in the United Kingdom can address it. Where the French rate is higher, the credit wipes out the French tax on that slice but no refund of any difference is paid. Keep every British assessment and proof of payment, because the credit is never granted on bare assertions.

Two charges sit outside that credit and surprise newcomers after the first avis d’imposition (the tax assessment notice). The first is late-payment sanctions. Article 1727 of the General Tax Code warns 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”, any tax claim not paid by the legal deadline bears late interest, currently running month by month until payment. Article 1730 of the same Code adds: “Donne lieu à l’application d’une majoration de 10 % tout retard dans le paiement des sommes dues au titre de l’impôt sur le revenu”, any delay in paying income tax draws a 10 per cent surcharge. A newcomer who files correctly but pays the balance late therefore owes the tax, the monthly interest and the 10 per cent, and the treaty credit reduces none of these accessories. The second charge is social levies. Article L. 136-6 of the Social Security Code (Code de la sécurité sociale) provides 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”. Individuals fiscally domiciled in France are liable to a contribution on capital income assessed on the net amount used for income tax. Investment income, rental income and capital gains from the United Kingdom therefore attract French social charges even where the treaty credit neutralises the income tax on the same item, subject only to the European coordination rules for people affiliated to another state’s social system, a separate analysis that turns on your work situation and your S1 or A1 certificate.

The mechanics of the first filing deserve the same care as the law. Without a tax number you cannot file online, and creating access requires proving who you are: service-public.fr explains that creating online access requires an identity check performed through the local tax office (service des impôts des particuliers), at the counter or by post with identity documents, birth certificate and proof of French address. Visit that office early in the year of filing, request the paper forms 2042, 2042-C, 2047 and 3916, and file the complete bundle by the paper deadline, which falls in May, while online filers in later zones have until late May or June. Attach the 2047 country schedules, the 3916 for each account, copies of British assessments and payment proofs, and a short dated note stating your arrival date with the evidence behind it. The administration also computes your withholding rate (taux de prélèvement à la source) from this first return under Article 204 H of the General Tax Code, so errors in year one echo into the monthly deductions of year two until you have the rate corrected.

If the assessment that follows is wrong, the remedy is a formal claim, not a telephone call. File a réclamation contentieuse (a written claim for discharge or reduction) with the office that issued the notice, setting out each ground separately: domicile date, treaty article and credit computation, account declared on time, penalty disputed. Attach every exhibit the ground depends on, because the office decides on the file and the judge later reviews that same file. An informal recours gracieux (a request for leniency or remission of penalties) can run alongside the formal claim for the fines and surcharges, stressing first filing, spontaneous correction and good faith, but it never replaces the formal claim and its deadlines. If the office rejects the claim expressly or stays silent past the statutory reply period, appeal to the tribunal administratif (the administrative court) within the applicable time limit stated on the rejection, asking for discharge of the tax, restoration of the credit and cancellation of the penalties, with interest. The Versailles case shows what the judge examines: the exact account references, the exact years, the exact filer named on each return. Files win or lose on that level of precision, which is why keeping the arrival proofs, the 3916 receipts, the British assessments and the payment confirmations together from day one is the cheapest legal insurance a newcomer can buy.

One corrective tool deserves emphasis because newcomers discover omissions after filing. A spontaneous correction filed before any control or information request reaches the office is treated far more leniently than the same correction extracted under a sixty-day demand or after the arrival of exchanged bank data. If you realise in October that your May return omitted a Yorkshire building society account or a dividend voucher, file a corrected 3916 and a corrected 2047 immediately, keep the proof of filing, and mention the correction expressly in any subsequent correspondence. Spontaneity does not erase the fixed fine where the statute imposes it, but it powerfully supports requests for remission of penalties and interest, it demonstrates the good faith the Versailles court found missing, and it closes the file before the machinery of reassessment, monthly interest and the 10 per cent surcharge starts turning. The cheapest supplement to a first return is therefore a diary note six months later: re-read the return with fresh eyes, compare it against your bank statements, and correct without waiting.

Conclusion

Your first French return turns on four reflexes. Fix your domicile date with dated evidence and let the treaty tie-breaker confirm it where both countries claim you. Declare worldwide income received from that date on the 2042, detail every British item on the 2047, and remember that even treaty-exempt income must appear for the effective rate. List every British account on its own 3916 in your own name for the exact year, dormant accounts and closed accounts included, because the courts treat a single interest credit as use and a spouse’s later return as no cure. Claim the treaty credit with British assessments and payment proofs in hand, budget for social charges and for interest and surcharges if payment slips, and challenge any wrong assessment by written claim with exhibits rather than by telephone. The British-born claimant who lost nearly 110,000 euros of argument in Versailles this year lost on paperwork, not on principle: the account existed, the information had already crossed the Channel, and the corrective filings named the wrong filer for the wrong years. File completely, file in your own name and keep everything, and your first French tax return becomes what it should be: a routine administrative step in a successfully organised move.