You moved to France after Brexit, rented or bought a home, registered with the local surgery, and kept your banking where it was: a current account with a high-street bank, an instant-access savings account, and the cash ISA you have held for years. The money felt safely parked while you settled into French life. Then a letter arrives from the French tax office. It speaks of an amende, a fine, of 1,500 euros per undeclared foreign account, and it asks searching questions about the origin of the money. This scenario is now common. Since Brexit, British nationals living in France are third-country nationals in the eyes of French administration, their UK accounts are foreign accounts like any others, and the automatic exchange of bank information between tax authorities means the French administration often knows about those accounts before you mention them. The good news is that most of these situations can be organised and defended, provided you understand three things in order: whether France treats you as tax resident, how to declare every UK account properly, and how to challenge the parts of the bill that are wrong. This guide explains each stage in plain English, with the exact legal texts and court decisions that decide these cases.

I. Confirm That France Treats You as Tax Resident, Then File a Complete Return

Everything starts with residence. If France considers you tax resident, you must declare your worldwide income in France and list every foreign account, whether it earned a penny or not. If you are not tax resident, different rules apply. Getting this first question right determines everything that follows, so this first part walks through the residence test and the content of the return before turning to the account declaration itself.

A. How a British arrival works out whether France is now the country of tax residence and what that residence obliges you to declare

French domestic law sets the test in article 4 B of the Code général des impôts, the French tax code. It provides: “1. Sont considérées comme ayant leur domicile fiscal en France au sens de l’article 4 A : a. Les personnes qui ont en France leur foyer ou le lieu de leur séjour principal ; b. Celles qui exercent en France une activité professionnelle, salariée ou non, à moins qu’elles ne justifient que cette activité y est exercée à titre accessoire”. In plain terms, three alternative gateways exist, and meeting any one of them is enough: your foyer, meaning the home where your family life is centred, or your main place of stay is in France; your professional activity is in France unless it is merely secondary; or the centre of your economic interests is in France. In practice, a British national who lives year-round in a French home with a spouse or partner, whose children attend a French school, and who works remotely for French clients or has retired to France with French-centred daily life will normally satisfy the first test without any need to examine the others. Physical presence matters too: spending more than 183 days in France in a calendar year points strongly toward French residence, although the statute does not reduce to day-counting alone and the administration looks at the whole pattern of life.

Two refinements matter for British readers. First, the same article adds a treaty safety valve: “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.” (article 4 B, treaty override) This means the double tax convention between France and the United Kingdom can, in a split-life case, allocate residence to one country only, even where domestic law would treat you as resident. A couple dividing time between Kent and the Dordogne, with a permanent home in each country, is the classic example where the treaty tie-breaker decides the outcome rather than French domestic law alone. Our detailed analysis of that split-life problem is set out in our pillar guide to how British couples prove tax residence when they live between France and the UK, which you should read alongside this article if your family straddles the Channel.

Once French residence is established, the filing obligation is broad. Article 170 of the Code général des impôts 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”. The déclaration d’ensemble des revenus, the overall income tax return, is filed each spring on form 2042, with foreign income detailed on the annexe form 2047 and foreign accounts listed on form 3916, which this article examines in depth below. The return covers worldwide income: French wages, UK rental income from a buy-to-let you kept, interest from a UK savings account, dividends from UK shares, and gains you realised during the year. Article 120 of the Code général des impôts confirms the reach into foreign investment income: “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”. A UK dividend or a distribution from a UK fund therefore falls squarely inside the French return, subject only to the credit mechanism of the double tax convention that prevents the same income being fully taxed twice.

British savers should pause on one persistent myth: the UK cash ISA. In Britain, interest inside an ISA grows free of UK tax, and many arrivals assume the wrapper travels with them. It does not. France does not recognise the ISA as an exempt envelope, so interest arising inside a cash ISA held by a French resident is taxable in France and must appear on the return, and the account itself must be declared on form 3916. The same reasoning applies to Premium Bond prizes and interest on ordinary UK savings: the UK treatment decides the UK bill, while the French return follows French categories. Deadlines add pressure. The online filing calendar each spring sets staggered dates by département, usually from late May to early June, and a first return after arrival often has to be filed on paper or through a newly created online account on the impots.gouv.fr portal. Missing the deadline does not merely delay matters: as the second part of this article explains, late and incomplete returns attract percentage surcharges on top of the flat fines for undeclared accounts, so diarising the date in your first year matters as much as any technical argument.

Practical organisation repays effort here. Before you sit down to file, assemble the UK tax year statements for every account, including accounts you closed during the year and joint accounts held with a spouse, because closure and joint ownership never remove the declaration duty. Convert sterling amounts using a consistent annual average rate and keep the calculation. Identify which income the United Kingdom has already taxed, because that tax is the raw material of the treaty credit claim you will make on the French side. And open the impots.gouv.fr guidance on form 3916, the foreign account declaration form alongside the English-language page of the public service portal at service-public.fr on declaring accounts opened abroad, so that each entry on your return has a visible counterpart in the official instructions. With the residence question answered and the income mapped, the next step is the declaration that causes most British fines: form 3916.

B. Declare every UK account on form 3916, including the accounts that earned nothing, and understand the presumptions that punish silence

The legal core of these cases is short and strict. Article 1649 A of the Code général des impôts provides: “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.” Every word counts. Personnes physiques domiciliées en France means you, once French resident. En même temps que leur déclaration de revenus means the account declaration travels with the annual return, on form 3916. And ouverts, détenus, utilisés ou clos, opened, held, used or closed, means the duty catches the current account you use daily, the savings account you barely touch, the ISA you consider a tax wrapper rather than an account, the joint account shared with your spouse, each account you closed during the year, and even electronic money or payment accounts held with a UK institution where they function as accounts. An account that earned no interest is still an account: the declaration duty does not depend on income, and telling the administration that an account produced nothing is done by declaring it, not by omitting it.

The same article then reverses the burden of proof against anyone who stays silent. It continues: “Les sommes, titres ou valeurs transférés à l’étranger ou en provenance de l’étranger par l’intermédiaire de comptes non déclarés dans les conditions prévues au deuxième alinéa constituent, sauf preuve contraire, des revenus imposables.” Transfers through an undeclared account are presumed to be taxable income unless you prove otherwise, with sauf preuve contraire meaning unless you bring evidence to the contrary. The courts apply this mechanism exactly as written. In a judgment of 27 February 2025, case number 23/00348, the Nancy judicial court set out the rule in these terms: “L’article 1649 A du code général des impôts instaure une obligation de déclaration des comptes bancaires ouverts, utilisés, détenus ou clos à l’étranger : « 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, utilisés, détenus ou clos à l’étranger. Les modalités d’application du présent alinéa sont fixées par décret. Les sommes, titres ou valeurs transférés à l’étranger ou en provenance de l’étranger par l’intermédiaire de comptes non déclarés dans les conditions prévues au deuxième alinéa constituent, sauf preuve contraire, des revenus imposables. »” The full decision is published at Cour de cassation portal, decision 67c0e1a16942c6b53b69f202. That couple held two Luxembourg accounts, and after partial discharge the court still taxed the unjustified foreign holdings at 60 percent. A British reader with an undeclared Barclays balance should read that outcome twice: once an account is known and unjustified, the administration does not need to trace each pound to a source of income.

How does the administration learn about the account in the first place. The honest answer is that it often already knows. Under the common reporting standard, the automatic exchange of financial account information, the United Kingdom passes account data to France each year, and the French administration matches that data against filed 3916 forms. Mismatches generate the letters British residents now receive. The administration then has a graduated set of tools. Article L. 23 C of the Livre des procédures fiscales, the tax procedure code, allows it to demand full information and supporting documents on the origin of the funds within sixty days where the declaration duty has been missed at least once in the previous ten years. Silence or an evasive reply at that stage triggers article L. 71 of the same code: “En l’absence de réponse ou à défaut de réponse suffisante aux demandes d’informations ou de justifications prévues à l’article L. 23 C dans les délais prévus au même article, la personne est taxée d’office dans les conditions prévues à l’article 755 du code général des impôts.” Taxée d’office means assessed by the office without your figures, and article 755 of the Code général des impôts then deems unjustified foreign holdings to be an untaxed gift taxed at the highest gift rate: “Les avoirs figurant sur un compte détenu à l’étranger, au sens du deuxième alinéa de l’article 1649 A, sur un contrat de capitalisation ou un placement de même nature souscrit à l’étranger, au sens de l’article 1649 AA, ainsi que les crypto-actifs figurant dans un portefeuille de crypto-actifs et les crypto-actifs uniques et non fongibles, au sens de l’article 1649 bis C, 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 assujetti, à la date d’expiration des délais prévus au même article L. 23 C, aux droits de mutation à titre gratuit au taux le plus élevé mentionné au tableau III de l’article 777”. That top rate is 60 percent, exactly the rate applied in the Nancy case. The chain from an unanswered letter to a 60 percent assessment is therefore short, mechanical, and entirely documented in the statutes.

Two judicial warnings complete the picture and both favour careful taxpayers. First, the Cour de cassation, the supreme court for civil and commercial matters, censured a court of appeal that had taxed foreign holdings on thin evidence. In its judgment of 7 May 2025, appeal number 24-11.883, published at Cour de cassation portal, decision 681af4ec0dfb1f09369ce0e7, the commercial chamber quashed the Nîmes appeal ruling and held: “l’administration fiscale ne peut réintégrer dans l’assiette de l’ISF des avoirs figurant sur un compte bancaire que si elle établit que ces avoirs composent le patrimoine du contribuable au 1er janvier de l’année considérée.” The administration must prove the funds actually belonged to you at the relevant date; presumptions about who held an account are not enough. For a British resident, this means bank statements proving that a balance was yours, or was not yours, are decisive evidence rather than background paperwork. Second, time does not necessarily heal an omission. Article L. 169 of the Livre des procédures fiscales extends the recovery period dramatically where foreign disclosure failed: “Le droit de reprise de l’administration s’exerce jusqu’à la fin de la dixième année qui suit celle au titre de laquelle l’imposition est due, lorsque les obligations déclaratives prévues aux articles 123 bis , 209 B , 1649 A , 1649 AA , 1649 AB et 1649 bis C du code général des impôts n’ont pas été respectées.” Ten years instead of three. The same article spares modest holdings: the ten-year extension does not apply where the taxpayer proves that “le total des soldes créditeurs de ses comptes à l’étranger n’a pas excédé 50 000 € à un moment quelconque de l’année”, the total credit balances of the foreign accounts never exceeded 50,000 euros at any point in the year (article L. 169, small-balance exception). A UK account forgotten in the return for the year of arrival can therefore be picked up many years later, with interest running throughout. The rational response is a full historical review: list every UK account for every year since arrival, file the missing 3916 forms, and correct the income returns before the administration writes to you, because spontaneous correction always costs less than correction under investigation.

II. Add Up the Fine, the Surcharge and the Interest, Then Challenge What Is Wrong

Once the filing position is rebuilt, attention turns to the bill. French tax penalties stack: a flat fine per undeclared account, percentage surcharges on late or understated tax, and late-payment interest. Each layer has its own legal basis, its own conditions, and its own defences. This second part prices each layer with a worked British example and then gives the step-by-step method for correcting the return and contesting the assessment.

A. How the 1,500 euro fine, the 10 and 40 percent surcharges and the monthly interest combine on a typical British file

Start with the flat fine, because it applies even where no tax was lost. Article 1736 of the Code général des impôts 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.” Each undeclared account costs 1,500 euros. A British household that kept three UK accounts, for example a current account, a savings account and a cash ISA, and declared none of them faces 4,500 euros of fines for one year, before any tax or surcharge. The statute raises the fine to 10,000 euros per account only where the account sits in a state with no administrative assistance convention with France, and the United Kingdom has such assistance arrangements, so British cases normally stay at 1,500 euros per account. That single fact is worth verifying on every notice, because a notice that applies the higher rate to a UK high-street account contains an error you can challenge immediately. Note also that the fine is annual: the same undeclared account can generate a fresh fine for each year it stayed off form 3916, which is why multi-year omissions escalate so fast and why historical correction matters.

Next come the surcharges on the tax itself. Article 1728 of the Code général des impôts targets late returns: “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”. The rate is 10 percent where you file on your own initiative or within thirty days of a formal demand, and 40 percent where you file more than thirty days after that demand. Take a concrete illustration. Suppose your French return omitted 2,000 euros of UK savings interest, generating roughly 600 euros of additional French tax at a 30 percent marginal rate. A spontaneous late correction adds about 60 euros. The same correction after an ignored formal demand adds about 240 euros. The arithmetic rewards speed at every stage, and the cheapest moment to act is always now.

The heavier surcharge punishes deliberate understatement rather than mere delay. Article 1729 of the Code général des impôts, as quoted by the Paris Court of Appeal in its judgment of 14 November 2022, case number 20/16282, published at Cour de cassation portal, decision 63733e4e48c76adcd126831a, provides: “Les inexactitudes ou les omissions relevées dans une déclaration ou un acte comportant l’indication d’éléments à retenir pour l’assiette ou la liquidation de l’impôt ainsi que la restitution d’une créance de nature fiscale dont le versement a été indûment obtenu de l’Etat entraînent l’application d’une majoration de 40 % en cas de manquement délibéré.” Forty percent for manquement délibéré, a deliberate failure. The same judgment states the safeguard that accompanies it: “La preuve du manquement délibéré du contribuable incombe à l’administration fiscale en application de l’article L. 195 A du livre des procédures fiscales, le caractère intentionnel du manquement du contribuable à son obligation déclarative devant être établi au moment de la déclaration inexacte ou incomplète.” The administration must prove intent at the date of the faulty return; confusion in a first year after arrival, reliance on the mistaken belief that an ISA is exempt, or an error by an adviser who was never told about the UK accounts all undermine that proof. In the Paris case itself, the court granted partial discharge of the deliberate-failure surcharges for a spouse taxed on omissions attributable only to the other spouse before they shared a household for tax purposes, holding that penalties are personal. A British couple where one partner managed the UK accounts while the other never saw a statement should keep that personalisation principle firmly in mind.

Finally, interest runs on top of everything. Article 1727 of the Code général des impôts establishes that any tax debt unpaid by the legal deadline bears late-payment interest, with statutory exceptions for disclosed positions and good-faith interpretative difficulties that rarely help an undeclared account. Interest accrues month by month until payment, so a ten-year recovery under article L. 169 carries ten years of interest arithmetic. Return to the worked example to see the stack. Three undeclared UK accounts over two years: 9,000 euros of flat fines, plus the tax on the omitted UK interest for each year, plus 10 or 40 percent on that tax depending on how each return was filed, plus monthly interest, plus, in the worst case where a sixty-day information request goes unanswered, the 60 percent gift-tax assessment on the balances themselves under article 755. No British household should pay that stack unexamined, because each layer can be tested, and the next section explains how.

B. Correct the return spontaneously and challenge the assessment through each procedural stage without missing a deadline

The method has a fixed order: correct first, document second, contest third, and never let a deadline pass while preparing the next step. Correction starts online. The impots.gouv.fr personal account allows a corrective return, a déclaration rectificative, for the current filing season, and missing 3916 forms can be added for the years concerned. A spontaneous correction before any administration contact removes the factual basis for the deliberate-failure narrative, reduces the surcharge rate under article 1728, and demonstrates the good faith that colours every later discussion. Attach a short explanatory note in French or English stating when you arrived, when you understood the duty, and what you are adding. Keep the acknowledgment of receipt: in tax litigation, the taxpayer who proves the date of filing controls the timeline.

If the administration has already written, the sixty-day information request under article L. 23 C becomes the most important letter you will receive. Answer it within the sixty days with bank statements for every account, evidence of the origin of the funds such as UK payslips, sale deeds, inheritance documents or transfer slips showing savings built from taxed earnings, and a schedule reconciling each balance with the corrected returns. The Nancy judgment shows what happens otherwise: unanswered or thinly answered requests end in taxation d’office at 60 percent. If the administration then proposes to reassess, it must in principle follow the adversarial procedure. Article L. 55 of the Livre des procédures fiscales provides: “Sous réserve des dispositions de l’article L. 56, lorsque l’administration des impôts constate une insuffisance, une inexactitude, une omission ou une dissimulation dans les éléments servant de base au calcul des impôts, droits, taxes, redevances ou sommes quelconques dues en vertu du code général des impôts ou de l’article L. 2333-55-2 du code général des collectivités territoriales, les rectifications correspondantes sont effectuées suivant la procédure de rectification contradictoire définie aux articles L. 57 à L. 61 A.” Contradictoire means you must be heard. Article L. 57 of the same code requires a reasoned adjustment proposal: “L’administration adresse au contribuable une proposition de rectification qui doit être motivée de manière à lui permettre de formuler ses observations ou de faire connaître son acceptation.” You reply with observations, and article L. 11 of the same code sets the background rhythm for tax correspondence: “A moins qu’un délai ne soit prévu par le présent livre, le délai accordé aux contribuables pour répondre aux demandes de renseignements, de justifications ou d’éclaircissements et, d’une manière générale, à toute notification émanant d’un agent de l’administration des impôts est fixé à trente jours à compter de la réception de cette notification.” Thirty days from receipt is the default heartbeat of these exchanges, and a proposal that is unreasoned, unsigned by the competent officer, or notified outside the recovery period is vulnerable on those grounds alone.

The formal contest follows the assessment notice, the avis de mise en recouvrement. File a written claim, a réclamation contentieuse, with the tax office that issued the notice, identifying each disputed item separately: the number of accounts counted for the flat fines, the applicable rate of each surcharge, the treaty credit for UK tax already paid, and the personalisation of penalties between spouses. The claim must observe the strict deadline printed on the notice, so check that date before perfecting the argument and send the claim by a traceable method. If the administration rejects the claim expressly or by silence, the dispute moves to the administrative court, the tribunal administratif, within the appeal period stated in the rejection. Before the judge, the arguments this article has assembled fit together: the treaty residence position for split-life households; the Cour de cassation rule that ownership of the funds at the relevant date must be proved rather than presumed; the absence of proven intent defeating the 40 percent deliberate-failure surcharge; the personal nature of penalties between spouses; and the documentary proof that UK-source income already bore UK tax that the convention requires France to relieve. Each point should be evidenced: passports and utility bills for presence, employment contracts for professional activity, UK P60s and P45s for taxed earnings, and complete statements for every account.

Do not neglect the British side of the file while fighting the French side. When you leave the United Kingdom, file form P85 with HM Revenue and Customs and review your residence position for the year of departure, following the official guidance at gov.uk on tax if you leave the UK to live abroad and gov.uk on moving or retiring abroad. A correct UK split-year position supports the treaty credit claim in France and prevents the worst outcome of all: full taxation in both countries with relief in neither. Keep every UK assessment, coding notice and certificate of tax paid, because the French claim for a treaty credit succeeds only with proof of the foreign tax actually levied. Where the file is large, professional help at this stage costs far less than a 60 percent assessment that hardens into a final debt for want of a timely reply.

Conclusion

A British resident who kept UK accounts after moving to France is not an unusual case and is not a hopeless one. French law draws a clear line between the taxpayer who organises the file and the taxpayer who ignores it. Residence under article 4 B decides the scope of the duty; the worldwide return under articles 170 and 120 carries the income; form 3916 under article 1649 A lists every account, however small or dormant; and each layer of the bill, from the 1,500 euro fine in article 1736 through the surcharges of articles 1728 and 1729 to the interest in article 1727, has conditions the administration must prove. The courts enforce those conditions strictly: the Cour de cassation quashed an assessment built on presumptions about account ownership, the Nancy court taxed unjustified holdings at 60 percent where the holders could not justify them, and the Paris court discharged deliberate-failure surcharges that were not personal to the person charged. Your task is therefore practical rather than theoretical. List every UK account since arrival, file the missing declarations, answer every administration letter within its stated days with statements and proof of origin, and challenge each line of the assessment separately and on time. Done in that order, most British files end not with the frightening stack described above but with the correct tax, a reduced penalty, and a clean file for the years ahead.

Need a quick opinion on your case

Book a telephone consultation in English within 48 hours with a lawyer of the firm about your French tax position. Call +33 6 46 60 58 22 or write through our contact page with a copy of your assessment notice and your list of UK accounts. You will receive a first assessment of your residence position, your declaration duties and your realistic chances of reducing the bill.