You have left Britain, the boxes are in a French hallway, and then the tax year turns. There is no Unique Taxpayer Reference on the mat, and often no numéro fiscal (the thirteen-digit French tax identification number) either. What arrives, if anything arrives, is a letter you cannot log into, or an avis d’impôt (income-tax assessment notice) that looks as if France has taxed a whole British year. Whether you are resident — foyer (the home where the household actually lives), work and the centre of your money — is set out in our guide to French tax residence after Brexit. This article is the next crisis: how a British arrival files the first French income-tax return, which forms go with it, and how to challenge the first bill.
French law splits the year of arrival. Article 166 of the code général des impôts (CGI, the French tax code) says that income whose taxation is triggered by establishing domicile in France “ne sont comptés que du jour de cet établissement”. Before that day France taxes you, if at all, as a non-resident on French-source income. After that day it taxes worldwide income. The first déclaration d’ensemble des revenus (the annual income-tax return, form 2042) is how that split is declared, with form 2047 for foreign income and form 3916 for UK accounts. Missing it is not clerical. Article 1728 of the CGI adds 10 per cent, then 40 per cent after a mise en demeure (formal notice to file). Undeclared British accounts carry a separate fine. A British newcomer often has neither a login nor a pre-filled form.
I. How do I file my first French tax return after moving from the UK?
A. When do I get a numéro fiscal and which form do I file in the year I arrive?
Residence is the gateway. Article 4 A of the CGI states: “Les personnes qui ont en France leur domicile fiscal sont passibles de l’impôt sur le revenu en raison de l’ensemble de leurs revenus. Celles dont le domicile fiscal est situé hors de France sont passibles de cet impôt en raison de leurs seuls revenus de source française.” Article 4 B then treats you as having a French tax domicile if you have in France your foyer or the place of your principal stay, a principal professional activity, or the centre of your economic interests. The same article adds that a person who meets one of those tests “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.” If both France and HMRC claim you, the 19 June 2008 France-United Kingdom convention, published by decree no. 2010-20 of 7 January 2010, is the tie-breaker. It is not the first return itself. The return assumes a position on residence and then declares the income that follows from it.
The Cour administrative d’appel de Paris (Paris administrative court of appeal) has restated the order of analysis. In CAA Paris, 5th chamber, 20 October 2023, no. 22PA00816, the court held: “Si une convention bilatérale conclue en vue d’éviter les doubles impositions peut, en vertu de l’article 55 de la Constitution, conduire à écarter, sur tel ou tel point, la loi fiscale nationale, elle ne peut pas, par elle-même, directement servir de base légale à une décision relative à l’imposition.” French law first; the treaty second. On the foyer the same judgment said that, for a single taxpayer without dependants, “le foyer d’un contribuable célibataire, sans charge de famille, s’entend du lieu où il habite normalement et a le centre de sa vie personnelle, sans qu’il soit tenu compte des séjours effectués temporairement ailleurs en raison des nécessités de la profession ou de circonstances exceptionnelles.” Days spent in Britain on a spreadsheet do not, by themselves, move a Paris flat that is still the place you normally live. That is why a first return filed as a non-resident, while the family is already in France, is a gift to the office later.
Once domicile is established, the arrival year is not taxed as if you had lived in France since 1 January. Article 166 is short and it is still in force: “Lorsqu’un contribuable précédemment domicilié à l’étranger transfère son domicile en France, les revenus dont l’imposition est entraînée par l’établissement du domicile en France ne sont comptés que du jour de cet établissement.” The official commentary, BOI-IR-DOMIC-20 of 25 June 2014, repeats the same idea in administrative language: “le contribuable qui établit son domicile en France n’est taxable à raison de tous ses revenus, français ou non, que depuis la date d’acquisition de son domicile.” If you were not already taxable in France, paragraph 10 of that commentary is the rule for most British movers: “Le contribuable est alors imposable d’après l’ensemble des revenus, de source française ou non, qu’il a réalisés ou dont il a eu la disposition depuis la date de son arrivée en France.” If you already had French-source income — a let flat, a French pension, a French salary — paragraph 20 adds that income to the worldwide slice that starts on the transfer date. One assessment is issued for the calendar year. It is a single bill covering two legal periods, not two separate years.
The filing duty sits in article 170 of the CGI: “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.” You file in year N+1 for calendar year N. If you moved in September 2025, the first return is the spring 2026 campaign for 2025 income. BOI-IR-DOMIC-20, paragraph 160, tells you where to send it: “Les contribuables qui fixent leur domicile fiscal en cours d’année en France doivent déclarer leurs revenus de l’année de transfert dans les conditions de droit commun.” The return goes to the service des impôts des particuliers non-résidents (the non-resident individuals’ tax office) if you had French-source income before you moved, and to “du centre des finances publiques de son nouveau domicile, dans le cas où le contribuable ne percevait pas de revenus de source française avant son installation en France.” A British employee who arrives in Paris with no prior French income files with the local centre des finances publiques of the new address. A British owner who was already declaring French rents as a non-resident stays with the non-resident service for that first resident year; that service then hands the file on.
Identifiers are the first practical blockage. The direction générale des Finances publiques (DGFiP, the public-finances directorate) says, in its note “Je viens ou je reviens en France”, updated 17 December 2025: “Vous n’avez pas accès à la déclaration en ligne et devez donc remplir une déclaration papier si vous déclarez vos revenus et/ou votre patrimoine en France pour la première fois.” That sentence matters. Service-Public fiche F358, checked on 5 June 2026, says online filing is obligatory if the home has internet. The two statements are not a contradiction once you distinguish a first-time filer from a returning one. Without a numéro fiscal and an online access number you cannot create the “espace Finances publiques”. The first return is therefore usually a paper form 2042, downloaded from impots.gouv.fr, signed, and posted to the office that BOI-IR-DOMIC-20 designates. If the office has already written to you with a numéro fiscal and an access number, the first-time page on impots.gouv.fr, modified on 30 March 2026, tells you to create the online space and, for the revenu fiscal de référence (reference tax income), to enter “0”. Do not invent a British Unique Taxpayer Reference in that box. Do not wait for a pre-filled return. There is nothing to pre-fill if France has never seen you.
The content of the arrival-year return is a split, not a British “whole year then claim relief”. The same DGFiP note says, for a person who had no French filing duty abroad: “Vous devrez indiquer la totalité des revenus que vous avez perçus depuis la date de votre retour jusqu’au 31 décembre N.” Service-Public fiche F31443 on return from expatriation, checked on 15 April 2026, gives the mirror image for someone who already declared French-source income as a non-resident: French-source income from 1 January until the return date, then French and foreign income from the return date until 31 December. In that case the paper file is form 2042-NR for the non-resident slice and form 2042 for the resident slice. A British newcomer who never had French-source income does not need 2042-NR. A British newcomer who was already letting a French house does. The date of “établissement du domicile” is a fact: the day the foyer moved, the day the family actually lives here, not the day the visa was stickered and not the day the notary handed over keys to a house that had been a holiday home for years.
Pay-as-you-earn starts in the same year. Article 204 A of the CGI provides that salaries, pensions, business profits and property income “donnent lieu, l’année au cours de laquelle le contribuable en a la disposition ou de leur réalisation, à un prélèvement.” That prélèvement à la source (withholding at source) is not the annual return. It is an advance. A new arrival with a French employer will see a default rate until the first return produces a personalised rate. F31443 warns that if you do not adjust the rate you may overpay, with repayment only after the following year’s assessment, or underpay and face a balance. The first 2042 is how the rate is later corrected. It is also how any UK pension paid without French withholding is brought into the French computation.
B. What UK income, bank accounts and treaty credits go on forms 2042, 2047 and 3916?
Worldwide income, from the day domicile is established, means what it says. UK employment income paid after the move, UK rents, UK dividends, UK interest, and UK pensions that the treaty does not exclusively assign to Britain belong on the French return. Form 2042 is the summary. Form 2047 is the annex for income received abroad. Form 2044 is the annex for French property income if you let a French flat. None of those annexes is optional window-dressing. Article 170 requires a detailed declaration of the income and of the family charges needed to compute the tax. If you leave the UK pension off the 2042 because “HMRC already taxed it”, you have filed an incomplete return. The treaty credit is claimed on the French return; it is not a reason to omit the income.
The method of relief is conventional, not a guess. Official commentary BOI-INT-DG-20-20-100 of 19 February 2020 states: “S’agissant des conventions fiscales conclues par la France, pour les résidents, deux méthodes d’élimination de la double imposition sont envisagées : – méthode 1 : l’octroi d’un crédit d’impôt égal au montant de l’impôt payé dans l’autre État à raison des revenus de source étrangère dont le résident de France est le bénéficiaire.” The other method is exemption with progression, a credit equal to the French tax corresponding to the foreign income. Which method applies to which UK income is a question of the 2008 convention article by article — employment, pensions, dividends, interest, capital gains — and of the protocol published with decree no. 2010-20. It is not a single “foreign tax credit” copied from a US 1040. UK dividends no longer carry the old imputed tax credit that existed under the 22 May 1968 convention. BOI-INT-CVB-GBR-10-30 records that residents of France “ne bénéficient plus en France d’un crédit d’impôt égal au crédit d’impôt britannique et imputable sur l’impôt français afférent à ces dividendes” for dividends paid from 18 December 2009. Declaring a ghost tax credit on a 2025 return is a way to draw a proposed correction.
UK bank accounts, ISAs, NS&I products and most brokerage accounts are a separate duty. Article 1649 A of the CGI 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.” The form is 3916 or 3916-bis. An ISA is not invisible because it is tax-free in Britain. Residence in France makes the account a foreign account. The same article adds that sums transferred through undeclared accounts “constituent, sauf preuve contraire, des revenus imposables.” That presumption is why a first return that lists the pension and forgets the Halifax current account is more dangerous than it looks. The detailed treatment of interest, ISAs and form 3916 is in our article on UK savings and bank accounts. The first-year point is simpler: you declare the accounts for the year in which you became resident, including accounts opened, held, used or closed after the move, and you do not wait until the second French year “when you have a login”.
UK rental income on a house you kept in Kent or Manchester is declared as foreign property income, not as if the UK return were enough. The treaty typically gives the United Kingdom the primary right to tax immovable property situated there, with France taxing its resident and giving credit. The mechanics sit on form 2047 and in the credit boxes of the 2042. They are not a reason to omit the rents. Our article on UK rental income of French residents deals with the credit and the social charges. On the first return the recurring error is to declare the rents from 1 January even though article 166 counts only from the day domicile was established, or the opposite error: to declare nothing because the UK agent already sent a statement to HMRC.
Family status goes on the same 2042. Married couples and partners bound by a French pacte civil de solidarité (PACS, the civil solidarity pact) generally file a joint household return. An unmarried British couple who have not entered a PACS file separately. Children in the French home affect the family quotient. A spouse who remained in Britain is not a detail for later: it is evidence on the foyer itself, which is why the residence article and this filing article have to be read together. If the family home is still in Surrey, the first 2042 filed as a French resident is the wrong document. If the family home is now in Lyon, omitting the spouse and filing as a single person is a different kind of wrong document.
Proof should be assembled before the envelope goes. The date of arrival can be shown by the lease or the notarial occupancy, school enrolment, utility contracts, the residence permit or Withdrawal Agreement card, and the day the UK address ceased to be the household address. Income is shown by UK P60s, pension payslips, bank statements and, where a credit is claimed, evidence of UK tax actually paid. BOI-INT-DG-20-20-100 is explicit that a credit equal to foreign tax paid presupposes tax “établi conformément” to the convention. A withholding that HMRC should have refunded is not a French credit. Keep the paper file. The first-year online space, if you later obtain one, will not contain the paper 2042 you posted unless the office has scanned it.
II. What if the first avis d’impôt is wrong or I missed the deadline?
A. How long do I have to challenge the first income-tax bill?
The first French bill is often the first time a British arrival realises that France has annualised a partial year, ignored a treaty article, or taxed UK interest that should have carried a credit. The remedy is not a complaint to HMRC and it is not a phone call that “puts a note on the file”. It is a réclamation contentieuse (a formal claim) under the livre des procédures fiscales (LPF, the tax-procedure code). Article L. 190 of the LPF sends to the contentious jurisdiction claims that seek “soit la réparation d’erreurs commises dans l’assiette ou le calcul des impositions, soit le bénéfice d’un droit résultant d’une disposition législative ou réglementaire.” A wrong arrival date, a missing article 166 split, a missing treaty credit and a surcharge that should not have been applied are all in that list.
Time is short and it is not the British four-year window. Article R*. 196-1 of the LPF, in the version in force from 30 July 2026, provides: “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 ; b) Du versement de l’impôt contesté lorsque cet impôt n’a pas donné lieu à l’établissement d’un rôle ou à la notification d’un avis de mise en recouvrement ; c) De la réalisation de l’événement qui motive la réclamation.” For income tax the usual clock is 31 December of the second year after the year of mise en recouvrement (the date the assessment is put into collection). An avis issued in July 2026 for 2025 income is, if collected in 2026, generally claimable until 31 December 2028. Waiting “until we are settled” is how that date is missed.
The Cour administrative d’appel de Douai has applied that clock to a taxpayer who said he only saw the bill on his online account years later. In CAA Douai, 4th chamber, 19 December 2024, no. 23DA00997, the court quoted article R. 196-1 and held: “le délai de réclamation court, en ce qui concerne l’impôt sur le revenu, de la date de la mise en recouvrement. Toutefois, lorsqu’il est établi que le contribuable n’a pas reçu l’avis d’imposition du fait d’une erreur de l’administration, le point de départ du délai de réclamation ne court qu’à compter de la date où il a connaissance de l’impôt.” The taxpayer had given a postal address on his 2017 return, had not told the office he had moved to Portugal, and discovered the 2018 bill on his online account in June 2021. The claim of 1 July 2021 was late. The court would not treat a later login as the starting point in the absence of an administrative error in sending the notice. A British newcomer who files a paper 2042 with a UK forwarding address, then moves inside France without telling the office, is in the same trap. Change of address is not a courtesy. It is what keeps article R*. 196-1 running from a notice you actually receive.
If the claim is rejected, or not fully accepted, article L. 199 of the LPF opens the administrative court: “En matière d’impôts directs et de taxes sur le chiffre d’affaires ou de taxes assimilées, les décisions rendues par l’administration sur les réclamations contentieuses et qui ne donnent pas entière satisfaction aux intéressés peuvent être portées devant le tribunal administratif.” Income tax is an impôt direct. The tribunal administratif of the département, in Paris the Tribunal administratif de Paris, is the court. You do not start in the judicial court. You do not start in the Conseil d’État. A claim that has never been put to the administration is not a court case. The two-month period for bringing the court action runs from notification of the decision on the claim, with a deemed rejection if the office stays silent for the statutory period. Diary both dates. Paying the bill does not stop the claim; collection continues unless a stay is sought and granted. A claim can ask for discharge of tax that article 166 did not allow, for a credit the convention requires, and for discharge of a surcharge that article 1728 did not allow.
A dual claim by HMRC and the French office is not solved by filing the French return alone. The 2008 convention contains a mutual agreement procedure. BOI-INT-CVB-GBR-10-30 records that the request “doit être présentée dans les trois ans qui suivent la première notification de la mesure qui entraîne une imposition non conforme aux stipulations de la convention ou, ce qui constitue une spécificité de cette nouvelle convention, dans les six ans qui suivent la fin de l’année fiscale ou de la période d’imposition au titre desquelles cette imposition est établie ou proposée, selon le délai le plus favorable au contribuable.” That procedure sits beside the French réclamation, not in place of it. Missing the French claim while waiting for a competent-authority letter is how both clocks run out. The Paris court of appeal’s reminder in no. 22PA00816 remains the method: French law first, then whether the convention displaces it. A first avis that taxed worldwide income from 1 January, although you only moved in October, is a French-law error under article 166 before it is a treaty error.
Typical first-bill defects are repetitive. The office has no date of arrival and taxes the British year in full. The office has the date but has left UK interest without the credit. The office has treated a UK ISA as undeclared income under the article 1649 A presumption because form 3916 was blank. The office has used a default withholding rate and then assessed a balance as if the default were a penalty. Each defect is a different legal plea. A catch-all letter that says “I am British, this is double tax” will be rejected. The claim should identify the year, the date of the avis, the date domicile was established, the income that belongs before that date, the income that belongs after it, the convention article invoked, and the documents. Attach the paper 2042 as filed. If you never filed, say so: the litigation then moves to the surcharge and to a late return, which is the next sub-part, not to a credit you never asked for.
B. Late-filing surcharges, undeclared UK accounts and a mise en demeure
The surcharge for a late or missing 2042 is in article 1728. In the version in force on 21 February 2026 it reads, so far as relevant: “Le défaut de production dans les délais prescrits d’une déclaration ou d’un acte comportant l’indication d’éléments à retenir pour l’assiette ou la liquidation de l’impôt entraîne l’application, sur le montant des droits mis à la charge du contribuable ou résultant de la déclaration ou de l’acte déposé tardivement, d’une majoration de : a. 10 % en l’absence de mise en demeure ou en cas de dépôt de la déclaration ou de l’acte dans les trente jours suivant la réception d’une mise en demeure d’avoir à le produire dans ce délai ; b. 40 % lorsque la déclaration ou l’acte n’a pas été déposé dans les trente jours suivant la réception d’une mise en demeure d’avoir à le produire dans ce délai.” There is also an 80 per cent rate for a concealed activity, which is not the ordinary case of a British pensioner who did not know the form existed. The 10 per cent applies if you file late without being chased, or if you file within thirty days of the warning. The 40 per cent applies if the warning expires unused.
The Cour administrative d’appel de Marseille has construed that thirty-day period as a délai franc (a clear period that does not include the starting day). In CAA Marseille, 3rd chamber, 13 July 2022, no. 20MA02135, a couple received a mise en demeure on 16 September 2017. The minister wanted 40 per cent because they had not filed inside thirty days as the office counted them. The court held: “Il résulte des dispositions précitées de l’article 1728 du code général des impôts que le contribuable dispose d’un délai de trente jours, qui est un délai franc, pour déposer sa déclaration à la suite de la mise en demeure qui lui a été adressée par l’administration.” The period ran from 17 September to 17 October. Proof of posting on 17 October, under article L. 286 of the LPF, saved them from 40 per cent. The minister’s appeal was rejected. The lesson for a British arrival is not to play chicken with the envelope. It is to treat the mise en demeure as a clock that starts the next day, to keep the postmark, and to file even an incomplete 2042 rather than wait for a missing UK P60. A later correcting claim is cheaper than 40 per cent of the tax.
Inaccuracies on a return that was filed on time are not article 1728. They are article 1729 of the CGI: 40 per cent for a deliberate failure, 80 per cent for abuse of law or fraudulent conduct. A first-year omission of a UK pension, explained and repaired, is not automatically “deliberate”. The office has to establish intent. Silence after a mise en demeure is what turns a 10 per cent case into a 40 per cent case. A British taxpayer who never received the warning because it went to the holiday home, while the family lives in Paris, should say so in the réclamation and prove the living address. The Douai case shows that merely saying “I only saw it online later” is not enough if the office used the address you yourself declared.
Undeclared UK accounts are fined even if the underlying interest is small. Article 1736 of the CGI, IV, 2, 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.” The amount rises to €10,000 per account where the account is in a State that has not concluded with France an administrative-assistance convention giving access to bank information. The United Kingdom exchanges information with France. The ordinary first-year risk is therefore €1,500 per forgotten account, not the €10,000 tariff. Four forgotten ISAs and a current account are €7,500 before any tax on the interest. The presumption in article 1649 A that transfers through undeclared accounts are taxable income is the larger threat. The réclamation against that presumption is proof of the origin of the sums — savings accumulated while you were a UK resident, a house sale already taxed, a gift — not an argument that “ISAs are tax-free”.
A proposed correction, if the office opens an audit, arrives as a proposition de rectification under article L. 57 of the LPF: it “doit être motivée de manière à lui permettre de formuler ses observations ou de faire connaître son acceptation.” You have thirty days, extendable by thirty on a request sent before the deadline. The reply must meet the facts the office has used: the date of arrival, the UK income, the accounts. A general protest is treated as acceptance by silence. After the reply, or after silence, the assessment follows, and the réclamation clock of article R*. 196-1 starts from collection. Do not confuse the thirty-day L. 57 window with the thirty-day article 1728 window or with the two-year réclamation window. They are three different clocks on three different documents.
What you should not do is invent a nil return, backdate the move to 1 January to “keep it simple”, or leave the UK employed and claim to be a French non-resident while the children are in a French school. The Versailles court of appeal, in CAA Versailles, 1st chamber, 6 October 2020, no. 18VE03972, recalled articles 4 A and 4 B in a departure case and applied article 167 of the CGI to income up to the date of leaving France. Arrival is the mirror: article 166 from the date of coming. The administration can examine a personal tax position under article L. 12 of the LPF whether or not you still have a French domicile, if you have obligations in France. A first-year file that is internally consistent — date of move, income from that date, list of UK accounts, treaty credits that actually exist — is harder to reopen than a file that tries to be clever.
If the first campaign is already closed and you have filed nothing, file now. Article 1728 taxes the delay; it does not create an exemption. A spontaneous late 2042, with 2047 and 3916, still has to be assessed, but it is the 10 per cent world rather than the 40 per cent world, provided no mise en demeure has expired. If a mise en demeure is already in the house, count the clear thirty days, post the forms, keep the proof, and then claim against any tax that article 166 or the convention does not support. Paying a surcharge you do not owe, in order to “clear the name”, is how people finance a bill that a réclamation would have reduced.
Conclusion
The first French income-tax return after a move from Britain is not a translation of self-assessment and it is not the eighteen-year-old’s first 2042 described on Service-Public. Article 4 A taxes worldwide income once article 4 B finds a French domicile, unless the 2008 convention assigns residence to the United Kingdom. Article 166 then cuts the arrival year at the day domicile was established. Article 170 requires a detailed return. DGFiP’s own international pages say a first-time filer uses paper and declares from the date of arrival to 31 December. Form 2047 carries the UK income; form 3916 carries the UK accounts. Article 1649 A and article 1736 fine the forgotten account. Article 1728 fines the forgotten return, at 10 per cent and then at 40 per cent after a warning whose thirty days the Marseille court has treated as a clear period. Article R*. 196-1 gives until 31 December of the second year after collection to claim, unless the office itself mis-sent the avis. Article L. 199 then opens the administrative court. The cheaper file is the one that states the date of the move, lists the British income and the British accounts from that date, claims only the credits the convention actually gives, and diaries the claim period the day the first avis arrives.
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If you have just moved from the United Kingdom, cannot obtain a numéro fiscal, have received a first French income-tax bill that looks wrong, or have been given a mise en demeure to file, our firm offers a telephone consultation within 48 hours with a lawyer of the firm. Call +33 6 46 60 58 22 or write via our contact page. The firm advises clients in Paris and Île-de-France as well as British residents throughout France.