Thousands of British citizens who settled in France before or after Brexit still hold at least one account in the United Kingdom: a current account with a high-street bank, a savings account, Premium Bonds or other NS&I products, a share-dealing account, or an online account opened with a fintech. Many assume that, because these accounts are ordinary, fully taxed or even dormant, French law has nothing to say about them. That assumption is wrong, and it is expensive. Under the Code général des impôts (the French General Tax Code), every person whose tax domicile is in France must declare, each year and together with the annual income tax return, the details of every account opened, held, used or closed abroad. The declaration is made on form n°3916, now completed online for most taxpayers through the impots.gouv.fr account. Failure to file it exposes the taxpayer to a fixed fine of €1,500 per account and per year, and — far more seriously — allows the tax administration to treat the sums passing through an undeclared account as taxable income, and to reach back up to ten years. Since Brexit, British accounts are foreign accounts in the strictest sense: the United Kingdom is a third State, and the former European softness surrounding cross-border banking has disappeared. This article sets out, first, exactly which British accounts and products fall within the French declaration duty and how the courts define an account that is “used”; secondly, the sanctions that apply where the duty has been missed and the practical steps a British resident can take to regularise the position before the tax office writes first.
I. Which British accounts must a French tax resident declare after Brexit?
A. What does the declaration duty under article 1649 A actually cover?
The starting point is the personal scope of the duty. The obligation falls on every individual whose tax domicile is in France. The notion of tax domicile is defined by article 4 B of the General Tax Code, which treats as French tax residents, in particular, persons who have in France their foyer (their home, the place where the household ordinarily lives) or the place of their main stay. A British citizen who has moved the centre of family life to France — whether under a Withdrawal Agreement residence permit or under a long-stay visa obtained after Brexit — is therefore squarely within the scope of the rule, whatever passport is held and wherever the money happens to sit.
The core obligation is stated by article 1649 A of the General Tax Code. Its second paragraph provides that individuals, associations and non-commercial companies domiciled or established in 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” — are required to declare, at the same time as their income or profit return, the references of accounts opened, held, used or closed abroad. Four points in that single sentence deserve attention. First, the duty is annual: it attaches to each year’s income tax return, not merely to the year in which the account was opened. Secondly, it covers accounts that were closed during the year, so that closing a British account does not erase the duty for that year. Thirdly, it catches accounts merely “held”, even without movements. Fourthly, the information to be declared is the account’s references — the identity of the bank, the account number and the dates of opening and closing — together with the income produced, which is declared in the ordinary way.
The practical detail is fixed by article 344 A of annexe III to the General Tax Code. The accounts to be declared are those opened with any person, private or public, who habitually receives on deposit securities, titles or cash. That formulation is deliberately wide. It plainly covers British current accounts and savings accounts, but also accounts held with building societies, stockbrokers and investment platforms, and accounts opened with electronic money institutions. A Wise or Revolut account with a Belgian or Lithuanian IBAN is an account abroad. An NS&I holding, which is a deposit with a public body receiving funds habitually, falls within the same logic. The declaration of an individual must list the accounts opened, used or closed during the year by the declarant, by any member of the tax household, or by a person attached to that household — which means that a joint British account, or an account operated for a spouse, can create a duty for the French-resident declarant.
The notion of a “used” account has been refined by the highest administrative court. In a decision of 4 March 2019, n°410492, the Conseil d’État — the supreme court for tax litigation in France — held that a bank account cannot be regarded as having been used by a taxpayer for a given year unless that taxpayer has, during that year, carried out at least one credit or debit operation on the account. The court added, in terms that matter greatly for dormant British accounts: “Ne constituent pas de telles opérations, d’une part, des opérations de crédit qui se bornent à inscrire sur le compte les intérêts produits par les sommes déjà déposées au titre des années précédentes, et, d’autre part, des opérations de débit correspondant au paiement des frais de gestion pour la tenue du compte.” In other words, the mere automatic crediting of interest on sums already deposited, and the mere debiting of account-keeping fees, do not amount to use. An account on which nothing has happened except interest and bank charges is not “used” for that year. Caution is nevertheless required: the account may still be “held”, and the prudent position for any account with a positive balance is to declare it. The Conseil d’État’s ruling narrows the notion of use; it does not create a safe harbour for undeclared dormant accounts, and relying on it in a dispute means litigating against the administration.
Finally, the duty concerns the declaration of the account itself, which is separate from the taxation of the income the account produces. A British taxpayer in France must therefore do two distinct things each year: declare the existence and references of every United Kingdom account on form n°3916, and declare the interest, dividends and other income arising on those accounts in the income tax return, with double taxation relief where appropriate under the France–United Kingdom convention of 19 June 2008, which remains in force after Brexit and is listed on the gov.uk page on France tax treaties. Declaring the income without declaring the account does not satisfy the law; declaring the account without declaring the income does not either.
B. Which British products are caught, and which fall under a different duty?
For a British reader, the practical question is a product-by-product one. The following categories are caught by the form n°3916 duty. Ordinary current accounts with British banks, whether or not they receive a pension or rental income. Savings accounts with banks and building societies, including accounts that only credit interest. Accounts with National Savings and Investments, including Premium Bonds: NS&I is a public body receiving deposits habitually, and the holding must be declared even though winnings are a separate question of taxable income. Share-dealing accounts, stocks and shares ISAs held with a platform — on which see our article on the tax treatment of a UK ISA for a French resident after Brexit — and accounts with online brokers. Accounts with fintechs and electronic money institutions established outside France, including where the IBAN is Belgian, Lithuanian or Irish. Accounts closed during the tax year, which must be declared one last time with their closing date. And accounts held through a French non-commercial company, such as an SCI whose partners are British family members, because the duty expressly extends to sociétés n’ayant pas la forme commerciale, non-commercial companies.
Two neighbouring duties must not be confused with form n°3916. Life insurance contracts and capitalisation contracts taken out abroad — a category that includes many British endowment policies and insurance bonds — fall under article 1649 AA of the General Tax Code, a distinct declaration with its own fine of €1,500 per contract. Crypto-asset accounts held with platforms abroad fall under article 1649 bis C, with a fine of €750 per undeclared portfolio. The three duties are cumulative, not alternative: a British resident who holds a current account in London, an insurance bond with an Isle of Man insurer and a crypto account with a foreign platform has three separate declarations to make. For pensions, the analysis is different again: the pension itself is income, declared as such, and the wrapper in which it sits may or may not be a declarable account depending on its legal nature; our article on declaring a UK private pension in France after Brexit addresses that question.
Three common misconceptions deserve to be corrected directly. The first is the belief that accounts in sterling, or accounts in a country with which France exchanges information automatically, need not be declared. Automatic exchange under the Common Reporting Standard does not discharge the taxpayer’s own duty; it merely makes omission easier to detect, since the administration receives British account data every year. The second is the belief that a joint account belongs to the spouse who opened it. Under article 344 A, an account used by a member of the tax household must be declared, and a person who operates an account under a power of attorney is treated as using it. The third is the belief that a small balance is beneath the administration’s attention. The €1,500 fine is fixed per account and per year, whatever the balance; an empty account forgotten on the return generates the same nominal fine as a large one, even though the administration’s enforcement priorities naturally focus on material sums.
II. What are the sanctions for an undeclared British account, and how can the position be regularised?
A. Fine, income presumption, ten-year recovery and gift-tax requalification
The immediate sanction is the fixed fine provided by article 1736 of the General Tax Code, paragraph IV: €1,500 per undeclared account, per year of omission. The amount rises to €10,000 per account only where the account is situated in a State or territory that has not concluded with France an administrative assistance convention against tax fraud and evasion allowing access to banking information. The United Kingdom has concluded such instruments with France — the bilateral convention of 19 June 2008 contains exchange-of-information provisions, and both States apply the multilateral instruments underlying the Common Reporting Standard — so the standard fine for a British account remains €1,500. That is a modest comfort: five undeclared accounts over three years of omission represent a theoretical exposure of €22,500 in fixed fines alone, before any tax adjustment.
The fixed fine is not the principal danger. The third sentence of article 1649 A provides that sums, securities or assets transferred abroad, or received from abroad, through accounts not declared as required “constituent, sauf preuve contraire, des revenus imposables” — constitute, unless proof to the contrary is provided, taxable income. The burden of proof therefore reverses: the administration may tax the flows through the undeclared British account as if they were income, and the taxpayer must demonstrate that the sums were not taxable, were exempt, or had already been taxed. The Conseil d’État confirmed the mechanics of this presumption in a decision of 8 March 2023, n°463267, explaining that these provisions “prévoient qu’à défaut d’une telle déclaration, les fonds ayant transité par ce compte constituent des revenus imposables, sauf pour le contribuable à apporter la preuve que les sommes en question n’entraient pas dans le champ d’application de l’impôt ou en étaient exonérées, ou qu’elles constituaient des revenus qui avaient déjà été soumis à l’impôt” (Conseil d’État, 8 March 2023, n°463267). For a British resident, that means keeping the documentary evidence of the origin of every material transfer from a British account: sale proceeds of a UK property with the completion statement, an inheritance with the grant of probate, pension lump sums with the provider’s statement. Without such evidence, an innocent transfer of one’s own savings can be taxed as income.
The time available to the administration is extended precisely where the declaration duty was missed. Under article L. 169 of the Book of Tax Procedures (Livre des procédures fiscales, the code governing tax audits), the ordinary recovery period of three years extends to ten years where the obligations laid down by article 1649 A have not been respected. The same provision adds a targeted relief: where the taxpayer proves that the total credit balances of the foreign accounts did not exceed €50,000 at any time during the relevant year, the ten-year extension does not apply. A British household whose United Kingdom accounts never exceeded that threshold in aggregate therefore keeps the ordinary three-year protection; above it, a decade of omissions can be reopened.
Two further mechanisms complete the picture, and both are more severe than the fixed fine. Under article L. 23 C of the Book of Tax Procedures, where the article 1649 A duty has not been respected at least once in the preceding ten years, the administration may — outside any full audit — require the taxpayer to provide, within sixty days, all information and justification on the origin and manner of acquisition of the assets standing on the account. Where the answer is absent or insufficient, article 755 of the General Tax Code provides that the unexplained assets are deemed, until proof to the contrary, to be an estate acquired gratuitously, taxable as a gift at the highest marginal rate — 60 per cent between non-relatives — at the date on which the sixty-day period expires. The Court of Cassation examined the compatibility of this system with European principles in a decision of 17 September 2025, n°23-10.403 (Cass. com., 17 September 2025): the commercial chamber held that the taxation of assets on an undeclared foreign account pursues the legitimate aim of combating fraud and evasion, and that the limitation regime attaching to it is not, in that respect, disproportionate. The practical lesson is that neither the passage of time nor constitutional argument will reliably shield an undeclared account; regularisation is the rational course.
B. How should a British resident regularise before the tax office writes first?
The first step is a complete inventory. List every account and product held outside France by each member of the tax household: bank and building society accounts, NS&I holdings, brokerage and ISA platform accounts, fintech accounts, accounts closed in recent years, and accounts operated under a mandate. For each, note the institution, the account number, the opening date, the closing date where applicable, and the movements year by year. British banks will supply historic statements, and NS&I provides certificates of holding; these documents serve both the declaration and any future proof of origin of funds.
The second step is to file or correct the declarations. The form n°3916 is completed online within the impots.gouv.fr account as part of the annual return, by ticking the foreign-accounts section and adding each account’s references; a paper form remains available for those who file on paper. Where previous years were omitted, a corrective return can be filed for each open year, and the online correction service (“corriger ma déclaration”) allows amendment of recent returns directly. Spontaneous correction, before any approach by the administration, is materially better than correction after a letter: it demonstrates good faith, it limits the years exposed to the fixed fine, and it forecloses the argument that the omission was deliberate. Where income on the accounts was also undeclared, the corrective return must include the income, with interest for late payment; negotiating a reduction of penalties is easier when the taxpayer has come forward unprompted.
The third step is to build the evidence file for the origin of funds, because the presumption of taxable income attaches to flows, not merely to balances. For each significant transfer between a British account and France, retain the documentary chain: completion statements for property sales, probate documents for inheritances, provider certificates for pension commencement lump sums, employer letters for bonuses, and bank statements showing the path of the money. If a request under article L. 23 C is ever received, the sixty-day deadline is strict, and the answer must be organised and complete; the file assembled in advance is then decisive. It should also be remembered that once the accounts are declared, future years become simple: the online return pre-fills the accounts section, and the duty reduces to an annual check.
The fourth step, where the sums are material or the omissions span several years, is to take advice before filing anything. The choice between a straightforward corrective return and an accompanied voluntary disclosure, the calculation of the exposure to fixed fines, the availability of the €50,000 aggregate threshold that preserves the three-year limitation, and the response to any administrative letter are questions on which the facts of each household matter. A British resident who receives a letter from the Service des impôts des particuliers mentioning article 1649 A or article L. 23 C should treat the deadlines it contains as absolute and seek assistance immediately.
Conclusion
Since Brexit, every account that a British resident keeps in the United Kingdom is, for French tax law, an account abroad. Article 1649 A of the General Tax Code requires each French tax resident to declare annually, on form n°3916 attached to the income tax return, every account opened, held, used or closed outside France; article 344 A of annexe III defines the duty broadly enough to catch British bank, savings, NS&I, brokerage and fintech accounts, and the Conseil d’État’s case law reserves only the narrowest relief for accounts showing nothing but interest and account-keeping charges. The sanction architecture is deliberately dissuasive: a fixed fine of €1,500 per account and per year under article 1736, a reversal of the burden of proof that treats flows through undeclared accounts as taxable income, a ten-year recovery period under article L. 169 of the Book of Tax Procedures where balances exceed €50,000, and — for unexplained assets — a requalification as a taxable gift at the highest rate under article 755, confirmed as proportionate by the Court of Cassation in September 2025. None of this is a reason for alarm; all of it is a reason for order. A British household in France that inventories its United Kingdom accounts, declares them each year, corrects past omissions spontaneously and keeps the evidence of the origin of its funds removes the entire risk at trivial cost. The cabinet assists British residents with these declarations, corrective filings and responses to the tax administration, in English and in French.
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Source : Cour de cassation – Base Open Data « Judilibre » & « Légifrance ».