You open your online tax account, or an envelope with the blue Marianne logo lands on the doormat, and the news is bad: the French tax office believes you have paid too little income tax, and it wants the difference, plus interest, plus possibly a penalty of 40% or more. The letter is called a proposition de rectification, which means a proposal to correct your tax bill. For a British resident in France after Brexit, this moment is stressful for a second reason: you may wonder whether the reassessment comes from rental income in the United Kingdom that you thought was taxable only in Britain, from interest on an ISA you assumed was tax-free everywhere, or from a year when you were not sure whether you were tax resident in France at all. This article explains, step by step, what that letter is, what the tax office must put in it, how to answer within the strict 30-day time limit, and how to challenge the final bill before the tax commission, in a formal claim, and before the court if necessary. Every deadline and every remedy below comes from the French statute book and from recent court decisions quoted word for word.
I. You have just received a proposition de rectification: what the letter is and how to answer within 30 days
The proposition de rectification is the letter by which the French tax administration tells you that it has found an insufficiency, an inaccuracy, an omission or a concealment in the figures on which your tax was calculated, and that it intends to put the figures right. It is not yet the final bill. It is the opening of a formal discussion procedure called the procédure de rectification contradictoire, which means an adversarial correction procedure in which you have the right to reply before anything becomes final. The statute states the principle directly: where the tax office finds such a problem, “les rectifications correspondantes sont effectuées suivant la procédure de rectification contradictoire définie aux articles L. 57 à L. 61 A”, which means the corrections must follow the adversarial procedure set out in Articles L. 57 to L. 61 A of the Livre des procédures fiscales, the French tax procedure code (Article L55 of the Livre des procédures fiscales). Because you are resident in France, your worldwide income is in principle on the table: the Code général des impôts, the French general tax code, provides that “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”, meaning that anyone whose home or principal place of stay is in France, or who carries on a professional activity in France otherwise than incidentally, is treated as fiscally domiciled in France (Article 4 B of the Code général des impôts). Since Brexit, British nationals are third-country nationals with no EU-law shield against information requests, and banks, employers and the British tax authority HMRC exchange far more data with France than most newcomers realise. A reassessment is therefore often triggered by something you did not hide deliberately: UK rental profits you declared to HMRC but not in France, interest from an ISA or a British savings account, a capital gain, or a pension lump sum. The France-United Kingdom double tax treaty signed on 19 June 2008 normally prevents the same income being fully taxed twice, usually by giving France a tax credit for the British tax paid, but the treaty never exempts you from declaring the income in France in the first place.
A. What the tax office must put in the letter and why a vague reassessment fails
The single most important protection at this stage is that the letter must be reasoned. The law says: “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.” In plain English, the tax office must send you a proposal that is reasoned in enough detail to let you comment on it or accept it (Article L57 of the Livre des procédures fiscales). A compliant letter therefore identifies each tax and each year concerned, states the amount of the proposed extra charge, sets out the facts found during the check, and explains the legal reasoning applied to those facts. A letter that merely asserts that you owe a lump sum, without showing how the figures were reached, does not allow you to reply properly, and that defect can later destroy the whole reassessment before the judge. Read the letter with that test in mind: does it tell you which income, which year, which amount and which rule? If whole pages of figures arrive with no explanation, say so in writing in your reply, because the objection is strongest when raised from the very first response. Check also who received the letter. Many British clients are taxed jointly with a spouse under a single French household return, and problems arise when the follow-up correspondence goes to only one of them. The Court of Cassation, the highest French civil court, held on 2 April 2025, appeal number 23-14.865, that “Si l’administration fiscale peut choisir d’adresser la proposition de rectification à l’un seulement des redevables solidaires de la dette fiscale, la procédure ensuite suivie doit être contradictoire et la loyauté des débats l’oblige à notifier les actes de celle-ci à tous les redevables.” This means that even where the tax office may send the initial proposal to only one of the persons jointly liable for the tax debt, the procedure that follows must remain adversarial, and fairness in the conduct of the dispute obliges the administration to notify every subsequent step to all of the liable persons (Court of Cassation, commercial chamber, 2 April 2025, appeal no. 23-14.865). The same decision adds a point of real practical value: “L’irrégularité tirée du non-respect par l’administration fiscale de cette règle peut être soulevée par l’un quelconque des débiteurs solidaires, y compris par celui qui a été effectivement destinataire de l’acte en cause, sans qu’il lui soit besoin d’établir un grief.” In other words, any one of the jointly liable debtors can raise this procedural irregularity, even the one who did receive the document, and without having to prove any specific harm. If you are married or in a civil partnership and only one of you has been kept informed after the first letter, that is an argument to preserve now, not later. Finally, keep the envelope or the electronic notification record: time limits run from receipt, and the date of receipt is often disputed.
B. How to use your 30 days, get a 30-day extension and build your written reply
You have 30 days from receipt to reply, and this deadline is strict. The rule is general: “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.” That is 30 days from receipt of any notification from a tax officer to answer it (Article L11 of the Livre des procédures fiscales). Thirty days is short when you need bank statements from a British bank, a P60 or SA302 calculation from HMRC, or a completion statement from a former letting agent. The good news is that the law gives you a one-off extension if you ask for it in time: “Sur demande du contribuable reçue par l’administration avant l’expiration du délai mentionné à l’article L. 11 , ce délai est prorogé de trente jours.” At the taxpayer’s request, received by the administration before the Article L. 11 deadline expires, the period is extended by 30 days (Article L57 of the Livre des procédures fiscales). Send that extension request immediately, in writing, through your online tax account messaging service or by recorded delivery letter, before the first 30 days run out, and keep the proof of sending. Never let the deadline pass in silence: an unanswered proposal becomes a confirmed reassessment almost automatically, and you lose your cheapest opportunity to kill the case early. A strong written reply has four ingredients. First, answer every point in the proposal in the same order, conceding nothing by implication; state clearly which corrections you accept, if any, and which you reject. Partial acceptance is allowed and often sensible, because it narrows and cheapens the rest of the dispute. Second, attach the evidence: French and British tax returns for the years in question, HMRC tax calculations and payment receipts, bank statements showing the real amounts received, tenancy agreements and letting accounts for UK rental income, and any treaty-based computation showing the foreign tax credit you claim in France. Third, set out your legal position simply: tax residence and the scope of worldwide taxation, the treaty article that allocates the taxing right or grants the credit, and any factual error such as a confusion between gross and net rent, a duplicated amount, or income that belongs to a different year. Fourth, close by expressly reserving all rights and requesting, if disagreement persists, referral to the advisory tax commission described in Part II. Write in French if you can, or have the letter translated; you may appoint another person to represent you by written authority, or instruct a lawyer, and the official guidance confirms that you can entrust a mandate to a representative or call on a lawyer when making a tax claim. Two British-specific traps deserve emphasis. ISAs have no equivalent in French law: interest sheltered from British tax inside an ISA is fully taxable in France for a French resident, and years of undeclared ISA interest regularly produce the reassessment. Likewise, UK rental profits must be declared in France even when correctly declared to HMRC; the treaty credit relieves double taxation but never replaces the French declaration. If either point appears in your letter, do not argue that the income was British-only; argue the correct taxable amount and the correct credit.
II. How to challenge the tax bill: the commission, the formal claim and the court
If your observations do not convince the tax officer, the administration confirms the reassessment and sends an avis de mise en recouvrement, which is the formal notice that the tax is now being collected. From that moment you move from discussion to challenge, and three layers of remedy exist: the advisory tax commission, the formal administrative claim called a réclamation contentieuse, and the administrative court. Understanding the order, the cost and the deadline of each layer is what turns a frightening bill into a manageable dispute. Start by checking the age of the years being reassessed, because the tax office does not have forever. The ordinary rule is: “Pour l’impôt sur le revenu et l’impôt sur les sociétés, le droit de reprise de l’administration des impôts s’exerce jusqu’à la fin de la troisième année qui suit celle au titre de laquelle l’imposition est due.” For income tax and corporation tax, the administration’s right to reassess runs until the end of the third year following the year for which the tax is due (Article L169 of the Livre des procédures fiscales). A reassessment of 2021 income notified at the end of 2024 is therefore in principle timely, while 2020 income reassessed for the first time in 2025 is normally out of time. There are two important extensions. Where the taxpayer carries on a hidden activity or the income comes from such an activity, the period runs for ten years instead of three. And where the administration has filed a criminal complaint for tax fraud within the reassessment period, leading to a judicial investigation, a special extension applies. On that special extension, the Court of Cassation held on 30 November 2022, appeal number 20-22.383, that “le délai spécial de reprise prévu à l’article L. 188 B du livre des procédures fiscales ne s’applique pas aux seules impositions dues au titre des années visées par la plainte de l’administration fiscale, mais à toutes les impositions comprises dans le délai initial de reprise non expiré à la date du dépôt de ladite plainte.” The special reassessment period is therefore not limited to the tax years named in the administration’s criminal complaint; it covers all taxes still within the initial reassessment period on the date the complaint was filed (Court of Cassation, commercial chamber, 30 November 2022, appeal no. 20-22.383). For most British readers this extension will never apply, but if your reassessment concerns years of undeclared foreign bank accounts or undeclared rental income, check the dates with a lawyer, because the administration sometimes relies on the longer periods.
A. Asking the commission des impôts for an opinion and checking the three-year time limit
When disagreement persists after your written reply, you can require the administration to take the opinion of an independent advisory body before it confirms the bill. The text provides: “Lorsque le désaccord persiste sur les rectifications notifiées, l’administration, si le contribuable le demande, soumet le litige à l’avis soit de la commission des impôts directs et des taxes sur le chiffre d’affaires prévue à l’article 1651 du code général des impôts”, followed by a list of other competent bodies depending on the tax at stake. In short, where disagreement persists, the administration must, if you ask, submit the dispute for the opinion of the direct taxes commission or the equivalent competent body (Article L59 of the Livre des procédures fiscales). The commission des impôts directs et des taxes sur le chiffre d’affaires, the commission for direct taxes and turnover taxes, is a panel composed of representatives of the administration and of taxpayers, chaired by a judge from the administrative court. It hears you or your representative, examines the file, and gives a reasoned opinion on the facts, typically on valuations, on the reality of expenses, or on whether an activity was genuinely carried on. That opinion is advisory, not binding, but in practice it carries real weight: an administration that ignores a favourable opinion must explain itself, and a judge later reads the file knowing the commission sided with you. Ask for referral expressly in your response to the confirmation of the reassessment, identify the factual questions you want examined, and attend the hearing with your documents organised by year. For British cases, the commission is particularly useful where the dispute turns on facts rather than pure law: the net amount of UK rental profits after British letting costs, the true amount of ISA interest actually credited, the arm’s length value of a benefit, or the reality of your residence pattern in a disputed year. Combine this step with the time-limit check from the introduction to Part II. Work out, year by year, whether the three-year reassessment period in Article L169 had already expired when the proposal arrived, and raise expiry expressly: time-bar is a complete defence for the year concerned, and it must be argued, as the judge will not always raise it for you. If the administration answers that a longer period applies because of a hidden activity or a fraud complaint, ask it to identify precisely which legal provision and which facts it relies on, then test that answer against the 30 November 2022 decision quoted above. Finally, note the practical rhythm: referral to the commission suspends nothing by itself, so while the commission examines your file, prepare the formal claim described in the next section, because its deadline runs independently.
B. Interest, 40% and 80% penalties, the réclamation deadline and the two months to go to court
The confirmed bill almost always contains more than the tax itself: late-payment interest and possibly penalties. The interest rule is automatic: “Toute créance de nature fiscale, dont l’établissement ou le recouvrement incombe aux administrations fiscales, qui n’a pas été acquittée dans le délai légal donne lieu au versement d’un intérêt de retard.” Any tax debt not paid by the legal deadline gives rise to late-payment interest (Article 1727 of the Code général des impôts). The statute does, however, spare interest in defined situations, including where the taxpayer has openly disclosed on the return the legal or factual reasons for the disputed treatment; transparency at the declaration stage therefore pays twice, first on the merits and second on interest. Penalties are a separate layer, and the scale is fixed by law: “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 : a. 40 % en cas de manquement délibéré”, rising to 80% for abuse of law, fraudulent manoeuvres or concealment of part of a contract price. In plain terms, inaccuracies or omissions in a return attract a surcharge of 40% for a deliberate failure and 80% for the most serious cases (Article 1729 of the Code général des impôts). The 40% surcharge requires a deliberate element, not a mere mistake, so a first error by a newcomer unfamiliar with French worldwide taxation, promptly corrected with full disclosure, is the classic case for asking the administration and then the judge to cancel the penalty while keeping only the tax and interest. Always contest penalties separately and expressly, with reasons, because an unchallenged penalty becomes final even if the underlying tax is later reduced. The main remedy against the confirmed bill is the réclamation contentieuse, the formal contentious claim to the administration. It must be filed no later than 31 December of the second year following the year of collection or of the contested payment: “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” (Article R*196-1 of the Livre des procédures fiscales). The official citizen guidance confirms the same deadline in everyday language: for income tax, the claim must be filed before 31 December of the second year following the year of assessment shown on the tax notice, and if you receive no answer within six months you may take the matter to court (service-public.fr: complaints and court appeals in tax matters). File the claim online from your personal account on the tax website, in the secure messaging section, or by post, giving your name and address, the tax and years concerned, your reasons and your supporting documents; the tax site’s own guide describes the same online route (impots.gouv.fr: how to make a tax claim). A recent decision protects taxpayers who moved slightly too fast: the Court of Cassation held on 28 May 2026, appeal number 25-15.132, that “l’irrecevabilité d’une réclamation formée avant l’envoi d’un avis de mise en recouvrement peut être régularisée si les impositions litigieuses sont mises en recouvrement avant que le juge de l’impôt statue sur cette contestation.” A claim filed before the collection notice, normally premature, can therefore be regularised where the tax is put into collection before the tax judge rules (Court of Cassation, commercial chamber, 28 May 2026, appeal no. 25-15.132). The same ruling restates the deadline as follows: “Selon le a) de ce texte, pour être recevables, les réclamations relatives aux impôts autres que les impôts directs et les taxes annexes à ces impôts doivent être présentées à l’administration fiscale au plus tard le 31 décembre la deuxième année suivant la mise en recouvrement du rôle ou la notification d’un avis de mise en recouvrement.” Ask in the claim for a suspension of payment, known as sursis de paiement, while the dispute is examined, so that enforced recovery is paused; if the administration refuses the suspension, that refusal can itself be challenged quickly. Silence from the administration for six months counts as an implied rejection and opens the door to the court. The court deadline is then short: “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 seised by an appeal against a decision, within two months of notification of that decision (Article R421-1 of the Code de justice administrative). For income tax the competent court is the tribunal administratif, the administrative court, of your place of residence, with an appeal to the cour administrative d’appel and, on points of law, to the Conseil d’État. Put the two-month date in your diary the day the rejection arrives, because unlike the 30-day reply, this deadline cannot be extended by a simple request.
Conclusion
A French tax reassessment is a procedure with rules, not a verdict. Answer the proposition de rectification within 30 days, with an extension if you need it; attack vague reasoning and check who was notified; use the tax commission for factual disputes and test the three-year time limit for every year; then challenge interest and penalties separately, file your formal claim before 31 December of the second year, ask for suspension of payment, and go to the administrative court within two months if the administration says no. For a British resident, most cases are won or lost on three mundane points: declaring worldwide income even where the treaty gives a credit, proving the exact foreign amounts with HMRC documents, and never missing a deadline. Treat each letter as the start of a timetable, keep every proof of sending, and get advice as soon as the first envelope arrives rather than after the collection notice lands.
Need a quick opinion on your case?
If you have received a French tax reassessment or a proposition de rectification and you are not sure what to answer or how to challenge it, our office offers a telephone consultation within 48 hours with an avocat of the firm. Call +33 6 46 60 58 22 or write via our contact page. Maître Reda Kohen, avocat, advises British residents in France at every stage of the tax dispute procedure.