You moved to France with your Individual Savings Account intact, and your British bank keeps telling you the good news: the ISA is tax-free. In the United Kingdom that remains true. In France it is not. From the first year you count as resident for French tax purposes, every pound of interest, every dividend and every gain realised inside your cash ISA or your stocks and shares ISA belongs on your French tax return, taxed in France and declarable account by account on the foreign-account statement. The wrapper that sheltered you in Britain shelters nothing here, and the penalties for forgetting it are automatic: a fine for each ISA left off the statement, plus the tax, plus interest for late payment, plus in serious cases an 80% increase that replaces the fine. This guide explains the position exactly as it stands for a British reader living in France after Brexit. Part I describes what France taxes and how the bill is computed. Part II describes the yearly declaration routine and what to do when the tax office comes asking questions or sends a reassessment you want to challenge.<\/p>\n
Start with the British side, because the misunderstanding always starts there. The official British guidance states the domestic position in one sentence: France taxes you the moment you meet its own residence test, and that test is deliberately wide. Article 4 B of the Code g\u00e9n\u00e9ral des imp\u00f4ts<\/a>, the French tax code, provides: French residents pay French tax on their worldwide income. Article 158 of the Code g\u00e9n\u00e9ral des imp\u00f4ts<\/a> states the rule without ambiguity: The decisive point is that no French provision recognises the ISA as a shelter. France knows its own exempt wrappers, the Livret A, the plan d’\u00e9pargne en actions, the assurance-vie after the holding period, each created by a statute that spells out the exemption. The British ISA has no equivalent statute on the French side, and the Franco-British double tax treaty of 19 June 2008, published by decree of 7 January 2010<\/a>, contains no article preserving foreign savings wrappers either. The treaty allocates taxing rights over dividends and interest, which helps you avoid double taxation, but it never says that income a contracting state exempts domestically must be exempt in the other state. So the interest that London ignores, Paris taxes; the dividend that London ignores, Paris taxes; and the gain realised on a disposal inside your stocks and shares ISA, which London ignores, Paris taxes in the year of disposal even if the proceeds stay inside the account. Each sale your broker executes within the wrapper is a taxable disposal for French purposes in that calendar year, with its own acquisition price, sale price and resulting gain or loss to compute and keep evidence for.<\/p>\n Apply this to each flavour of ISA you may hold. A cash ISA produces interest, taxed as investment income in the year it is credited. A stocks and shares ISA produces dividends when portfolio companies distribute, interest when bond funds pay out, and capital gains whenever holdings are sold at a profit, each stream taxed in France in the year it arises. A Lifetime ISA adds two wrinkles: the 25% British government bonus is a receipt with no exempting provision on the French side, so it joins worldwide taxable income like any other receipt, and the British 25% withdrawal charge you suffer on an unauthorised withdrawal is not a deductible French expense. A Junior ISA held for a child who lives with you in France follows the same logic: the child is generally fiscally domiciled with the parents, the income is taxable, and the declaration duties described in Part II fall on the parents to perform. Finally, respect the British contribution rule quoted above. Paying into the ISA after you have become non-resident breaches British ISA rules and can cost the account its British relief, while changing nothing on the French side, where the income was taxable in any event. The clean routine is to freeze contributions when you leave, keep the account open, and handle everything through the French return.<\/p>\n France taxes investment income under a system whose official name you will meet on every notice: the pr\u00e9l\u00e8vement forfaitaire unique<\/em>, universally called the PFU or flat tax. Article 200 A of the Code g\u00e9n\u00e9ral des imp\u00f4ts<\/a> sets its income-tax component in these terms: Two withholding mechanisms sit in front of the final bill, and both name you expressly as the person concerned. For dividends, article 117 quater of the Code g\u00e9n\u00e9ral des imp\u00f4ts<\/a> provides: You are not locked into the flat tax. Article 200 A<\/a> continues: The treaty then decides what happens to any British tax on the same income. For dividends, article 11 of the Franco-British convention<\/a> provides: Two short worked pictures fix the orders of magnitude. Suppose your cash ISA credits \u00a31,000 of interest in the year and you are under the flat tax with no British withholding: France charges the flat-tax treatment on the full \u00a31,000 converted to euros at the year’s rate, roughly \u00a3300 of total charge at the standard combined rate, all of it payable in France. Suppose instead your stocks and shares ISA pays \u00a31,000 of dividends and you elect for the scale while your marginal band is 11%: only \u00a3600 enters the base after the 40% allowance, the income-tax element is about \u00a366, and the social levies apply on top, with part of the CSG deductible next year. Change the marginal band to 41% and the same election costs about \u00a3246 of income tax on the \u00a3600, which is why the flat tax usually wins higher up the scale. These are illustrations, not computations for your file: convert each receipt at the proper rate, apply the elections you actually made, and keep the broker statements that prove every figure.<\/p>\n This guide belongs to our ISA cluster whose first comprehensive treatment is Your ISA Is Not Tax-Free in France After Brexit: How a British Resident Declares It, Pays French Tax, and Challenges the Bill<\/a>; what follows deepens it with the 2008 treaty mechanics and the September 2025 Cour de cassation ruling on undeclared foreign accounts.<\/p>\n The declaration duty is separate from the tax charge and it is the duty that traps most British savers, because nothing in Britain prepares you for it. France requires residents to list their foreign accounts every single year, even accounts that earned nothing, even accounts you never touched. The official service-public guidance states the scope exactly: Timing and paperwork follow one simple rule. The guidance says: Build the routine once and repeat it every May. First, list every British account in your name and every account on which you hold a signing authority, including each ISA, and check whether any was opened, held, used or closed during the year. Second, collect the yearly statements from each provider showing interest credited, dividends paid, proceeds of disposals with acquisition prices, bonuses, charges and the sterling-to-euro conversions you will use, keeping the documents for at least the reassessment period. Third, complete one 3916 statement per account with the exact identification details the form asks for: the provider’s name and address, the account number, the dates of opening and closing where relevant. Fourth, report the income itself in the investment-income sections of the return, choosing flat tax or scale for the whole year as computed in Part I, and report securities gains in the gains section with their own detail. Fifth, verify before validating that the number of 3916 statements equals the number of foreign accounts you listed in step one. The most common errors are declaring the income but omitting the 3916, which still draws the fine; declaring one ISA and forgetting the second; treating a stocks and shares ISA as a single shareholding rather than an account to declare plus income to tax; and assuming that an account with no movements needs no statement, when a merely held account is expressly reportable. If you discover an omission from a past year, a spontaneous correction almost always costs less than waiting for the administration to find it through automatic exchange of bank information, which between France and the United Kingdom now runs as a matter of course.<\/p>\n Trouble usually announces itself politely, with a letter asking where numbers came from. The administration routinely sends information requests about foreign assets before any reassessment, and a recent decision of the Cour de cassation shows how heavily the rest of the case then weighs on your reply. On 17 September 2025 the commercial, financial and economic chamber of the Cour de cassation, appeal number 23-10.403, decision number 441 FS-B, rejected the appeal of a taxpayer pursued over Swiss bank accounts, and its statement of the facts deserves reading in full by anyone tempted to ignore such letters: You can save tax-free with Individual Savings Accounts (ISAs).<\/q> That sentence is correct as far as His Majesty’s Revenue and Customs is concerned. The same guidance then deals with your exact situation, a saver who leaves Britain:
If you open an Individual Savings Account (ISA) in the UK then move abroad and become a non-UK resident, you cannot put money into it (unless you’re a Crown employee working overseas or their spouse or civil partner).<\/q> You may keep the account, since the guidance adds:
However, you can keep your ISA open and you’ll still get UK tax relief on money and investments held in it.<\/q> So London tells you two things: stop paying in once you are non-resident, and enjoy continued British relief on what stays inside. Neither statement binds Paris in any way.<\/p>\n
Sont consid\u00e9r\u00e9es 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 s\u00e9jour principal ; b. Celles qui exercent en France une activit\u00e9 professionnelle, salari\u00e9e ou non, \u00e0 moins qu’elles ne justifient que cette activit\u00e9 y est exerc\u00e9e \u00e0 titre accessoire ;<\/q> In plain terms, your home or your main place of stay (in French, your foyer<\/em> or place of principal stay), your professional activity, or the centre of your economic interests can each be enough. Most British settlers meet the first test within months: the family home is in France, the children are at a French school, daily life happens here. From that point you are a person fiscalement domicili\u00e9e en France<\/em>, fiscally domiciled in France, and the whole machinery described below applies to you for the full calendar year concerned.<\/p>\n
Les revenus nets des diverses cat\u00e9gories entrant dans la composition du revenu net global sont \u00e9valu\u00e9s d’apr\u00e8s les r\u00e8gles fix\u00e9es aux articles 12 et 13 et dans les conditions pr\u00e9vues aux 2 \u00e0 6 ter ci-apr\u00e8s, sans qu’il y ait lieu de distinguer suivant que ces revenus ont leur source en France ou hors de France.<\/q> Net income in each category goes into total net income under the same rules whether its source is French or foreign. And foreign investment income is expressly caught: article 120 of the same code<\/a> treats as revenue
Les dividendes, int\u00e9r\u00eats, arr\u00e9rages et tous autres produits des actions de toute nature et des parts de fondateur des soci\u00e9t\u00e9s, compagnies ou entreprises financi\u00e8res, industrielles, commerciales, civiles et g\u00e9n\u00e9ralement quelconques dont le si\u00e8ge social est situ\u00e9 \u00e0 l’\u00e9tranger quelle que soit l’\u00e9poque de leur cr\u00e9ation<\/q>. Interest credited inside a cash ISA and dividends paid on shares held inside a stocks and shares ISA therefore enter your French taxable income in the year they arise, whether or not you withdraw a penny from the wrapper.<\/p>\n
B. How your ISA interest, dividends and gains are actually taxed: the flat tax and the progressive-scale option<\/h3>\n
Le taux forfaitaire mentionn\u00e9 au premier alin\u00e9a du pr\u00e9sent 1 est fix\u00e9 \u00e0 12,8 % ;<\/q> The official service-public guidance confirms the architecture:
Le pr\u00e9l\u00e8vement forfaitaire unique est constitu\u00e9 de l’imp\u00f4t sur le revenu (12,8 %) et des pr\u00e9l\u00e8vements sociaux.<\/q> In the standard case for investment income this produces the familiar overall charge of 30%, combining the 12.8% income-tax charge with the social levies, and that is the figure to use when you budget. One composition detail is worth knowing exactly as the administration states it for people affiliated to a neighbouring social security system:
Si vous r\u00e9sidez en France, travaillez dans un pays de l’EEE ou en Suisse et \u00eates affili\u00e9 \u00e0 la s\u00e9curit\u00e9 sociale obligatoire de ce pays, vous n’\u00eates pas soumis \u00e0 la CSG et \u00e0 la CRDS. Seul le pr\u00e9l\u00e8vement de solidarit\u00e9 de 7,5 % est d\u00fb.<\/q> Since Brexit the United Kingdom is no longer in that group, so most British settlers in France pay the full social-levy element; if you hold an S1 certificate or a cross-border affiliation, have the levy mix checked rather than assuming either rate.<\/p>\n
Les personnes physiques fiscalement domicili\u00e9es en France au sens de l’article 4 B qui b\u00e9n\u00e9ficient de revenus distribu\u00e9s mentionn\u00e9s aux articles 108 \u00e0 117 bis et 120 \u00e0 123 bis sont assujetties \u00e0 un pr\u00e9l\u00e8vement au taux de 12,8 %.<\/q> For interest and similar fixed-income products, article 125 A of the same code<\/a> opens in the same way for
Les personnes physiques fiscalement domicili\u00e9es en France au sens de l’article 4 B qui b\u00e9n\u00e9ficient d’int\u00e9r\u00eats, arr\u00e9rages et produits de toute nature de fonds d’Etat, obligations, titres participatifs, bons et autres titres de cr\u00e9ances, d\u00e9p\u00f4ts, cautionnements et comptes courants<\/q>. In practice your British ISA provider operates no French withholding at all, so nothing is taken during the year and the whole charge is settled when you file the return; the mechanism matters mainly if you also hold French-paying investments, where you can ask the paying institution for exemption from the advance withholding when your reference income is modest, a request the administration says must reach the institution
au plus tard le 30 novembre de l’ann\u00e9e pr\u00e9c\u00e9dant celle du paiement<\/q>, no later than 30 November of the year before payment.<\/p>\n
Par d\u00e9rogation au 1, sur option expresse du contribuable, l’ensemble des revenus, gains nets, profits, plus-values et cr\u00e9ances mentionn\u00e9s \u00e0 ce m\u00eame 1 est retenu dans l’assiette du revenu net global d\u00e9fini \u00e0 l’article 158.<\/q> On your express election, all the income and gains otherwise under the flat tax go into total net income and face the progressive scale instead, and
Cette option globale est exerc\u00e9e lors du d\u00e9p\u00f4t de la d\u00e9claration pr\u00e9vue \u00e0 l’article 170, et au plus tard avant l’expiration de la date limite de d\u00e9claration.<\/q> The election is all-or-nothing for the year: every item of investment income and every gain on securities follows the same route. The official guidance explains the trade-off plainly. Under the flat tax you cannot use the 40% allowance on dividends, you cannot deduct part of the CSG, and you cannot deduct costs; under the scale you are taxed at your marginal band but you recover those three advantages, and the election covers all your investment income and securities gains together. Households with little other income, typically taxed at 11% or not at all, often gain from the scale; households already in the 30% band or above usually gain from the flat tax. Run both computations each year before ticking the box, because the right answer moves with your other income.<\/p>\n
Les dividendes provenant d’un Etat contractant et pay\u00e9s \u00e0 un r\u00e9sident de l’autre Etat contractant sont imposables dans cet autre Etat.<\/q> Both states may tax, but
si la personne qui les re\u00e7oit en est le b\u00e9n\u00e9ficiaire effectif, l’imp\u00f4t ainsi \u00e9tabli ne peut exc\u00e9der 15 % du montant brut des dividendes<\/q>, the source-state charge cannot exceed 15% of the gross where the recipient is the beneficial owner. For interest the treaty’s answer is cleaner. Article 12 of the convention<\/a> provides:
Les int\u00e9r\u00eats provenant d’un Etat contractant et dont le b\u00e9n\u00e9ficiaire effectif est un r\u00e9sident de l’autre Etat contractant ne sont imposables que dans cet autre Etat.<\/q> Interest whose beneficial owner lives in France is taxable only in France. In practice Britain levies no withholding on either stream for you, so there is generally no British tax to credit; where a withholding has been operated, article 200 A<\/a> answers that
L’imp\u00f4t retenu \u00e0 la source est imput\u00e9 sur l’imposition \u00e0 taux forfaitaire dans la limite du cr\u00e9dit d’imp\u00f4t auquel il ouvre droit, dans les conditions pr\u00e9vues par les conventions internationales.<\/q> The foreign withholding is credited against the flat-tax charge within the treaty credit limit. Readers who also receive British dividends outside the ISA will find the same mechanics explained step by step in our guide to British dividends and interest paid from the United Kingdom<\/a>, which works through declaration lines and the credit in detail.<\/p>\n
II. Declaring the ISA every year on form 3916 and challenging the bill when it goes wrong<\/h2>\n
A. The yearly 3916 declaration: which statement, which timing, which fines for each undeclared account<\/h3>\n
You must report to the tax authorities the foreign accounts if they were open, held, used or closed in the taxation year.<\/q> An ISA you simply left invested all year is a held account. An ISA you closed in March is a closed account. Both go on the statement. The same page explains which establishments count:
You must declare accounts domiciled outside France with a banking institution or with any financial services provider (notary, stockbroker, etc.).<\/q> Your cash ISA with a British bank and your stocks and shares ISA with a British broker or platform are both caught, and each ISA counts as its own account, so a saver with one of each files two lines, not one. If you doubt where an online account is domiciled, the administration gives a practical test based on the IBAN code of the account: a French IBAN starts with FR, and anything else is reported each year as a foreign account.<\/p>\n
Accounts opened abroad must be reported at the same time as your annual tax return.<\/q> You tick the foreign-accounts box on the income return and attach one statement per account, the form 3916 series, currently form 3916 and 3916 bis under Cerfa number 11916, which also covers digital-asset accounts and foreign life assurance. The legal anchor behind the form is article 1649 A of the Code g\u00e9n\u00e9ral des imp\u00f4ts<\/a>, and the sanction for skipping it is in article 1736 of the same code<\/a>, which provides:
Les infractions aux dispositions du deuxi\u00e8me alin\u00e9a de l’article 1649 A et de l’article 1649 A bis sont passibles d’une amende de 1 500 \u20ac par compte ou avance non d\u00e9clar\u00e9.<\/q> That is 1,500 euros per undeclared account, so two forgotten ISAs mean 3,000 euros before any tax is even discussed. The same paragraph continues:
Toutefois, pour l’infraction aux dispositions du deuxi\u00e8me alin\u00e9a de l’article 1649 A, ce montant est port\u00e9 \u00e0 10 000 \u20ac par compte non d\u00e9clar\u00e9 lorsque l’obligation d\u00e9clarative concerne un Etat ou un territoire qui n’a pas conclu avec la France une convention d’assistance administrative en vue de lutter contre la fraude et l’\u00e9vasion fiscales permettant l’acc\u00e8s aux renseignements bancaires.<\/q> The 10,000-euro level applies where the account sits in a state with no administrative-assistance treaty with France. The United Kingdom has such assistance arrangements with France, so the British ISA normally attracts the 1,500-euro fine rather than the 10,000-euro one, but do not read that as leniency: the service-public presentation of the sanctions adds that an
Increase of 80 % of the duties due on the amounts shown on the undeclared account(s). This increase then replaces the fine of \u20ac1,500 or \u20ac10,000.<\/q> Where tax was actually evaded on the sums in the account, an 80% increase on the duties can dwarf the flat fine, and it substitutes for it rather than adding to it.<\/p>\n
B. When the tax office reassesses you: answering the information request, filing the claim and going to court<\/h3>\n
le 3 f\u00e9vrier 2014, \u00e0 la suite de la transmission par un procureur de la R\u00e9publique, sur le fondement de l’article L. 101 du livre des proc\u00e9dures fiscales, d’informations selon lesquelles M. et Mme [H] auraient \u00e9t\u00e9 titulaires de comptes bancaires ouverts dans les livres d’une banque \u00e9tablie en Suisse<\/q>, the tax office questioned them about the origin of the funds, and then, the court records,
Par une proposition de rectification du 6 novembre 2015 notifi\u00e9e \u00e0 M. [H], l’administration fiscale a proc\u00e9d\u00e9 \u00e0 la taxation d’office aux droits de mutation \u00e0 titre gratuit des avoirs figurant sur les comptes bancaires litigieux au cours de la p\u00e9riode pr\u00e9cit\u00e9e, en application des articles L. 71 du livre des proc\u00e9dures fiscales et 755 du code g\u00e9n\u00e9ral des imp\u00f4ts.<\/q> Silence led to automatic taxation, taxation d’office<\/em>, of the account balances as undeclared gifts, and the courts upheld it. The full reference is available from the Cour de cassation, commercial chamber, 17 September 2025, appeal 23-10.403, decision 441 FS-B (rejection)<\/a>. Your ISA case would run under income-tax provisions rather than gift-duty provisions, but the procedural moral is identical: answer information requests completely, within the stated deadline, with documents, because non-response authorises the administration to assess on assumptions that are far harder to undo later.<\/p>\n