You moved from the United Kingdom to France after Brexit, you spent your first full year in your French home, and now the spring post brings a question you cannot ignore: how do you file your first French income tax return, the déclaration des revenus? Since 1 January 2021 British citizens have been third-country nationals in France, which changes nothing about the French tax code itself but changes everything about your paperwork trail: a first declaration filed on paper rather than online, British bank and savings accounts to list on a separate statement, British-source income to report even where Britain also taxes it, and a double tax treaty to stop the same pound being taxed twice. Get any of these wrong and France adds late-payment interest, surcharges and per-account fines automatically, while undeclared foreign balances can be presumed to be untaxed gifts at the top rate of gift duty. This guide explains, for a British reader, the day France starts taxing your worldwide income, the exact forms of your first return, the price of an omission, and how to challenge a bill you consider wrong. French legal terms are explained at first use. The law is stated as in force on 23 September 2026, with the exact statutory references you or your adviser can check on Légifrance.

I. Your First French Return Starts With Residence and Ends With the Right Forms

A. The day France starts taxing your worldwide income

French income tax does not depend on your passport. It depends on your domicile fiscal, your tax domicile. Article 4 A of the Code général des impôts (CGI), the French general tax code, draws the basic line: “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 French tax resident pays French income tax on worldwide income, while a person whose tax domicile is outside France pays it only on French-source income. The moment you settle in France permanently, your British salary residue, your UK rental income, your interest and your pension all enter the French picture, even if some of them remain taxable in Britain too.

Whether you are resident is tested against three alternative criteria, and meeting any one of them is enough. Article 4 B of the CGI provides: “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 ;” The foyer, the household, generally means where your spouse and children live; the séjour principal, the principal place of stay, is in practice where you spend most of the year, often measured against roughly 183 days. A third criterion, the centre of your economic interests, catches people whose money and business life sit in France even if their diary says otherwise. A British retiree who buys a house in the Dordogne, moves in with their spouse and spends ten months a year there is a French tax resident under the very first test. A consultant who keeps a London flat but works full-time from a Lyon office is caught by the professional-activity test unless that French activity is genuinely ancillary.

Domestic law is only half the answer, because the tax treaty can take residence back. Article 4 B itself warns that “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 France-United Kingdom treaty that decides this is the 2008 UK-France Double Taxation Convention, which the British government lists as the 2008 UK and France Double Taxation Convention — in force. Its Article 4 first defines a resident as a person liable to tax under a state’s laws by reason of domicile, residence or similar criteria, then settles dual residence with a strict cascade: “he shall be deemed to be a resident only of the Contracting State in which he has a permanent home available to him; if he has a permanent home available to him in both States, he shall be deemed to be a resident only of the State with which his personal and economic relations are closer (centre of vital interests)”. Only if that test fails do habitual abode, then nationality, then mutual agreement between the two tax authorities decide. A British newcomer who keeps a house available in Kent while buying in France therefore needs to know where their centre of vital interests truly lies, because that answer, not their nationality and not their UK tax residence certificate alone, allocates the taxing rights.

The Cour de cassation (Court of Cassation) enforces this allocation rigorously. In a judgment of 11 March 2026, Commercial, Financial and Economic Chamber, appeal no. 25-10.235, two taxpayers treated by the French administration as French-domiciled for 2007 and 2008 claimed Swiss treaty residence under lump-sum taxation. The Court approved the appeal court for holding that “M. et Mme [M], considérés par l’administration française comme des contribuables ayant leur domicile fiscal en France au titre des années 2007 et 2008, doivent démontrer non seulement que les autorités suisses leur attribuent la qualité de résident fiscal en Suisse, mais également qu’ils ont cette qualité au sens de cette convention.” Because their French-source privileged income of 402,745 euros exceeded the 278,788 euro lump-sum base on which they had been taxed in Switzerland, they were denied treaty residence for 2007. The treaty was different, but the method travels directly to British files: once France considers you domiciled on its soil, it is for you to prove treaty residence elsewhere within the meaning of the convention, figures in hand. Keep your tenancy agreements, travel records, family location evidence and proof of where your economic life sits, because the tie-breaker turns on facts, not on assertions.

One practical consequence follows for the year of arrival. France taxes residents on the income of the whole year of the move in most cases, so income received before the move can fall inside the first French return. Do not assume that January-to-arrival earnings stay invisible: list them, then claim the treaty allocation, rather than leaving the administration to discover them through international information exchange. That exchange is real, as the Versailles case discussed in Part II shows, where the French authorities acted on information received from the British tax authorities themselves.

B. Paper form 2042, foreign-income statements and the 3916 for your UK accounts

The filing duty itself is general and expressed in broad terms. Article 170 of the CGI states: “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 subscribe and send to the administration a detailed return of income and profits, family circumstances and the other elements needed to compute the tax. For a British newcomer, that means worldwide income from the year of arrival, including British wages, British rents, interest, dividends and pensions, each directed to its proper schedule, with the treaty then relieving double taxation by exemption or tax credit as the relevant treaty article provides. Our guide to how France taxes British pensions, state and private, after Brexit works through the pension corner of that same return in detail.

The first French return has one procedural trap that catches almost every British newcomer: it cannot be filed online. The English-language pages of the French tax administration state that “In 2026, you do not have access to the online tax return and must therefore send a paper return to your tax department if you are declaring your income and/or property assets in France for the first time.” Online filing is otherwise compulsory for anyone with internet access, but newcomers are routed to paper for year one. The same page confirms that “Standard returns are used (2042, 2044, etc.).” Form 2042 is the main return form; form 2044 covers property income. Download the forms from impots.gouv.fr, complete them by hand or on screen before printing, sign, and send them to the service des impôts des particuliers, the local personal-tax office, of your French home. Filing dates are set every year by the administration and differ between paper and online filers and between geographic zones, so check the campaign calendar for the year rather than relying on the previous year’s deadline. Keep proof of posting: a late first return attracts the same surcharges as any other late return.

Alongside the income schedules, British newcomers must file the foreign-account statement, form no. 3916, the déclaration par un résident d’un compte à l’étranger, the statement by a resident of an account held abroad. The statutory duty sits in Article 1649 A of the CGI: “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, at the same time as their income return, the details of accounts opened, held, used or closed abroad. Note the four verbs: an HSBC current account you kept in London, a savings account you emptied before the move, a joint account with your spouse, and an investment platform account you merely used during the year are all declarable. The common British mistake is declaring only the accounts that still hold money on 31 December; the statute expressly covers accounts used or closed during the year as well. Life-insurance style contracts held abroad fall under a parallel duty, so list those too rather than assuming a British wrapper is invisible to the French administration.

Build a small arrival file before you start writing. You will need your passport and residence permit, proof of the date you moved into the French home, the previous year’s British P60 or self-assessment return, statements for every British account open, used or closed during the year, details of any British property let or sold, and pension statements. Where a document is in English, the administration may ask for a translation; having one ready avoids the return sitting unprocessed while correspondence crosses the Channel. And where the figures are uncertain, file on time with your best estimate and correct afterwards through a claim, because a late return costs more than an amended one, as Part II explains.

II. The Price of Getting It Wrong, and How You Challenge the Bill

A. Interest, surcharges, the 1,500 euro fine and the Article 755 presumption

French tax sanctions stack, and they apply mechanically. First comes late-payment interest, the intérêt de retard. Article 1727 of the CGI provides: “Le taux de l’intérêt de retard est de 0,20 % par mois. Il s’applique sur le montant des créances de nature fiscale mises à la charge du contribuable ou dont le versement a été différé.” The rate is 0.20 per cent per month on the tax debt, running from the first day of the month after the tax should have been paid until the last day of the month of payment. On a 10,000 euro balance paid a year late, that is roughly 240 euros of interest before any penalty is added.

Then come the surcharges, the majorations, for filing late. Article 1728 of the CGI 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 ;” Failure to file on time draws 10 per cent where there was no formal demand, or where you file within thirty days of receiving a mise en demeure, a formal demand to file, and 40 per cent where you still have not filed thirty days after that demand; concealment of activity draws 80 per cent. A British newcomer who files the first 2042 three months late without any demand pays 10 per cent on the tax due plus monthly interest; one who ignores the demand letter pays 40 per cent. Interest and surcharges cumulate, so delay is the most expensive strategy available.

The foreign-account statement carries its own fines, per account. Article 1736 of the CGI provides: “Les infractions au premier alinéa de l’article 1649 A sont passibles d’une amende de 1 500 € par ouverture ou clôture de compte non déclarée.” Offences against the first paragraph of Article 1649 A draw a 1,500 euro fine per undeclared account opening or closure. And: “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.” Offences against the second paragraph draw 1,500 euros per undeclared account or advance. The same article raises the fine to 10,000 euros per undeclared account where the reporting duty concerns a state or territory with no administrative-assistance convention with France giving access to banking information. Three forgotten British accounts can therefore cost 4,500 euros in fines alone, before a euro of tax is discussed. Lesser omissions and inaccuracies in the statement draw 150 euros each, capped at 10,000 euros for information due together. Declare every account, including dormant and closed ones: the fine is per account, so completeness is cheaper than triage.

Beyond fines, undeclared foreign balances trigger a formidable presumption. Article 755 of the CGI, whose official text is published on Légifrance, deems unjustified foreign holdings to be gifts taxable at the top gift-duty rate. The Court of Cassation restated the mechanism on 6 November 2024, Commercial, Financial and Economic Chamber, appeal no. 23-15.183: “les avoirs figurant sur un compte ou un contrat d’assurance-vie étranger et dont l’origine et les modalités d’acquisition n’ont pas été justifiées dans le cadre de la procédure prévue à l’article L. 23 C du livre des procédures fiscales sont réputés constituer, jusqu’à preuve contraire, un patrimoine acquis à titre gratuit”, meaning holdings on a foreign account or life-insurance contract whose origin and acquisition details have not been justified under the Article L. 23 C procedure are presumed, unless the contrary is proved, to be assets acquired by way of gift. The same judgment shows the presumption is rebuttable with real evidence: the taxpayer had, for the part of the disputed holdings made up of interest produced by those holdings, “renversé la présomption énoncée à l’article 755 du code général des impôts en établissant que ces sommes, dont l’origine et les modalités d’acquisition étaient justifiées, ne constituaient pas un patrimoine acquis à titre gratuit”, overturned the Article 755 presumption by establishing that those sums, whose origin and acquisition details were justified, did not constitute assets acquired by way of gift, and the appeal court was overruled for refusing to subtract them. Paper trails beat presumptions; assertions do not.

A Versailles judgment of 7 May 2026 shows exactly how this machinery hits a British file. The Tribunal judiciaire de Versailles (Versailles Judicial Court), case no. RG 23/07001, dealt with a British-born taxpayer whose accounts in Britain and Malta came to light through information received from the British and Maltese tax authorities. After an unanswered request for information and explanations, the administration imposed taxation d’office, ex officio assessment, under Articles L. 23 C and L. 71 of the Livre des procédures fiscales (LPF), the tax procedure code, read with Article 755 of the CGI. The court held that the administration had met the conditions for those provisions, which establish a presumption that the holdings on the disputed British account were acquired by way of gift, in the court’s words: “Ces dispositions établissent une présomption d’acquisition à titre gratuit des avoirs figurant sur le compte litigieux britannique.” The presumption being a simple one, the burden moved to the taxpayer: “il s’agit d’une présomption simple et il appartient ainsi à Madame [B] [T] épouse [Q], qui conteste la taxation d’office, d’apporter la preuve de l’origine et des modalités d’acquisition de ces avoirs, conformément à l’article L.193 du livre des procédures fiscales précité.” A table summarising wages earned with her husband since 1998, unsupported by accounting or bank records showing payment into the disputed HSBC account, with payslips actually showing wages paid into different accounts and no trace of any transfer to the disputed one, did not prove that the 365,249 euro balance came from salaries. The court dismissed all her claims, refused any costs order in her favour and ordered her to pay the costs. For a British newcomer, the moral is concrete: keep every transfer slip between your British and French accounts, because ten years later a table reconstructed from memory will not move the court.

B. The claim first, then the judge: deadlines that forgive nothing

A French tax bill is never challenged by ignoring it. It is challenged by a réclamation, a formal claim to the administration, which alone opens the road to court. Article L. 190 of the LPF defines the claims that belong to the contentious jurisdiction: “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.” Claims seeking correction of errors in the basis or computation of tax, or the benefit of a right given by statute or regulation, go to the contentious judge. A British newcomer who believes the treaty exempts part of their income, who disputes the residence finding, or who contests a 40 per cent surcharge is squarely in this territory: write the claim, cite the treaty article or statute, attach the evidence.

Send the claim to the right office. Article R*190-1 of the LPF provides: “Le contribuable qui désire contester tout ou partie d’un impôt qui le concerne doit d’abord adresser une réclamation au service territorial, selon le cas, de la direction générale des finances publiques ou de la direction générale des douanes et droits indirects dont dépend le lieu de l’imposition.” A taxpayer wishing to dispute all or part of a tax concerning them must first send a claim to the local office of the Direction générale des finances publiques (DGFiP), the public-finances administration, for the place of taxation. In practice that is the office shown on your avis d’imposition, the tax assessment notice. Send it by registered letter with acknowledgment of receipt, keep the receipt, and diarise the reply: an express rejection, or prolonged silence, is what allows you to go to court next.

The claim itself has a guillotine deadline. Article R*196-1 of the LPF states: “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 ;” For admissibility, claims about taxes other than local direct taxes must reach the administration by 31 December of the second year following, as the case may be, the collection of the tax roll or notification of a recovery notice. A 2025 assessment notified in autumn 2026 must therefore generally be claimed by 31 December 2028. Miss that date and the claim is inadmissible however strong the merits, which is why a British newcomer who discovers an old error while preparing the next return should claim immediately rather than waiting.

If the administration rejects the claim, the tribunal administratif, the administrative court, is next, and its door also closes fast. Article R. 421-1 of the Code de justice administrative, the administrative justice code, provides: “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.” The court can only be seized by an action against a decision, within two months of notification or publication of the contested decision. Two months from the rejection letter, not from the original assessment and not from when you feel ready: instruct counsel at once, assemble the arrival file described in Part I, and plead the treaty tie-breaker or the factual justification with documents, not recollections. Courts decide these cases on traceability, as Versailles demonstrated, and traceability is built in year one, not in year ten.

Conclusion

Your first French tax return rewards method and punishes improvisation. Establish your residence position under Articles 4 A and 4 B and the 2008 treaty’s centre-of-vital-interests test before you write a single figure; file the paper 2042 on time with the 3916 listing every British account opened, held, used or closed; report worldwide income and let the treaty allocate it rather than hiding pre-arrival earnings. The sanctions for skipping steps are automatic and cumulative: 0.20 per cent monthly interest, 10 to 40 per cent surcharges, 1,500 euros per undeclared account, and a presumption that unexplained foreign balances are gifts taxed at the top rate, rebuttable only with real banking evidence. And where the administration is wrong, the path exists: a documented claim to the local office by 31 December of the second year, then the administrative court within two months of rejection. British newcomers who treat year one as the foundation of their French tax history, with papers kept and deadlines diarised, rarely become the cautionary tales of year ten.

Need a quick opinion on your case

A telephone consultation within 48 hours with a lawyer of the firm helps you check your residence position, your first return or your claim before the next deadline. First telephone consultation: 80 EUR incl. VAT. Call Maître Reda Kohen on +33 6 46 60 58 22, or use the contact page. The firm advises British newcomers in Paris and across Île-de-France as well as throughout France.