You have lived in France since before Brexit, or you arrived after it with a visa and a carte de s\u00e9jour<\/i> (residence permit), and now you are asking the next question: can I become French without giving up being British, and what happens if the administration says no? Since 1 January 2021 British citizens have been third-country nationals in France. That single fact reshapes the whole route to French nationality. Before the end of the transition period your right of residence derived from European Union law; today it derives from the Withdrawal Agreement or from an ordinary French residence permit, and every naturalisation file starts with proof that your residence is lawful, stable and centred in France. The good news is that France accepts dual nationality and the United Kingdom does too, so naturalisation does not require you to renounce your British passport. The harder news is that naturalisation by decree (naturalisation par d\u00e9cret<\/i>) is a favour, not a right: the Minister examines your residence, your assimilation, your language, your livelihood and your character, and may refuse or adjourn even a file that looks complete. This guide explains, for a British reader, the two routes that matter \u2014 naturalisation by decree after five years and acquisition by marriage declaration (d\u00e9claration \u00e0 raison du mariage<\/i>) \u2014 the documents and tests the prefecture (pr\u00e9fecture<\/i>, the local office of the State) will demand, and exactly how to challenge an inadmissibility decision (irrecevabilit\u00e9<\/i>), a rejection (rejet<\/i>), an adjournment (ajournement<\/i>) or an opposition to a marriage declaration.<\/p>\n
French terms appear in italics with a plain-English explanation at first use, because the prefecture interview and every decision letter will use them. All statutory references are to the provisions in force on 10 October 2026, checked on L\u00e9gifrance for this article, and every court passage quoted was read in the full text of the decision. The procedure described is the online filing route now generalised across France, with the two-month hierarchical appeal (recours hi\u00e9rarchique<\/i>) to the Minister and then the Administrative Tribunal of Nantes (tribunal administratif de Nantes<\/i>), the single court that hears naturalisation refusals for the whole country. Readers who are still securing their underlying residence should first read our guide to renewing the Withdrawal Agreement card and challenging a refusal or removal order: British WARP Card in France After Brexit: Renewing Your Withdrawal Agreement Residence Permit, Travelling on an Expired Card, and Challenging a Refusal or OQTF<\/a>.<\/p>\n The starting rule of naturalisation by decree is stated in one sentence of the Civil Code: Article 21-15 of the Civil Code<\/a> provides that “l’acquisition de la nationalit\u00e9 fran\u00e7aise par d\u00e9cision de l’autorit\u00e9 publique r\u00e9sulte d’une naturalisation accord\u00e9e par d\u00e9cret \u00e0 la demande de l’\u00e9tranger.” In plain English, nationality by decree is granted by the public authority on application; nothing is automatic, and the burden of proving each condition lies on you. The first condition is residence, and for British applicants since Brexit it has two layers: the European layer that used to protect you is gone, and the French layer must be proved document by document.<\/p>\n The residence condition itself has two limbs. First, the five-year qualifying period (stage<\/i>, literally the waiting period): Article 21-17 of the Civil Code<\/a> states that “la naturalisation ne peut \u00eatre accord\u00e9e qu’\u00e0 l’\u00e9tranger justifiant d’une r\u00e9sidence habituelle en France pendant les cinq ann\u00e9es qui pr\u00e9c\u00e8dent le d\u00e9p\u00f4t de la demande.” You must therefore show habitual residence in France throughout the five years before you apply. Habitual means more than physical presence on scattered dates. The prefecture looks for the centre of your material interests and family ties: where you work or run your life from, where your spouse and children live and go to school, where you pay tax as a resident, where your home actually is. The English-language service-public.fr page puts the warning bluntly for every applicant: that you must still be resident in France when the naturalisation decree is signed And it adds the sentence that sinks many files: that where the applicant lives in France while a spouse or children live abroad, French nationality may be refused For a British family that kept a house in Kent while renting in Lyon, with children still schooled in England, that warning is the whole case in miniature.<\/p>\n Second, residence must still exist on the day the decree is signed: Article 21-16 of the Civil Code<\/a> provides that “Nul ne peut \u00eatre naturalis\u00e9 s’il n’a en France sa r\u00e9sidence au moment de la signature du d\u00e9cret de naturalisation.” A file built on five solid years can therefore still fail if you move back to the United Kingdom while the file is pending, or if your centre of interests visibly shifts across the Channel during the eighteen months of examination. Keep your home, your tax residence and your daily life in France until the decree is published in the Journal officiel<\/i> (the official gazette in which decrees take legal effect).<\/p>\n Since Brexit, lawful residence has a specifically British layer. If you were settled in France before 31 December 2020, your lawful status is normally the Withdrawal Agreement residence card, the WARP card (carte de s\u00e9jour Accord de retrait du Royaume-Uni de l’Union europ\u00e9enne<\/i>), and the prefecture will check that it is valid and that you have not been absent so long as to lose the right. If you arrived after 2020, you hold an ordinary permit \u2014 visitor, employee, entrepreneur, family, student renewed into something stable \u2014 and the prefecture will check its continuity: gaps, expired cards left unrenewed, or long periods without any permit break habitual lawful residence even if you were physically in France. Students should note that years spent on a student permit count weakly and periods of unlawful presence count for nothing. Short absences for family visits or holidays do not break residence, but a six-month return to Britain to work, or a spouse and children permanently reinstalled in the United Kingdom, will be read as moving the centre of your life out of France.<\/p>\n The five-year period can be shortened in cases the Code lists exhaustively. The most useful for British readers is the two-year reduction: Article 21-18 of the Civil Code<\/a> reduces the stage to two years for a foreigner who has completed two years of higher education leading to a French university diploma, for a person who has rendered or can render important services to France by ability and talent, and for a person with an exceptional integration record in civic, scientific, economic, cultural or sporting life. A British graduate of a French university, a researcher recruited by a French laboratory, or an executive whose business record in France is genuinely remarkable should plead this reduction expressly with diplomas and evidence, not assume the prefecture will spot it. Full exemption from any waiting period (Article 21-20<\/a> covers French-speaking applicants schooled in French, and Article 21-19<\/a> covers refugees, veterans who served France and those who rendered exceptional services) rarely helps a standard British file, but a British spouse of a French citizen has a different and often faster route altogether, examined in Part II: the marriage declaration, which has its own four-year clock.<\/p>\n Practical consequences follow. Apply only when the five years \u2014 or the reduced two years with proof \u2014 are complete on the filing date, because the prefecture counts backwards from the receipt, not from the decision. File with unbroken evidence for every year: residence permits front and back, tax notices (avis d’imposition<\/i>), pay slips or business accounts, leases and utility bills, school certificates for children, and proof that absences were short and explained. If your spouse lives in Britain, either reunite the household in France before applying or expect an adjournment or rejection on centre-of-interests grounds, and take advice before paying for a file that the case law of the administrative courts will almost certainly uphold as refused. Where the household genuinely straddles the Channel for work reasons, document why France remains the centre \u2014 children schooled here, principal home here, tax residence here \u2014 rather than hoping the prefecture will not notice the London address.<\/p>\n Residence opens the door; four further filters decide whether you pass through. They are assimilation to the French community (assimilation \u00e0 la communaut\u00e9 fran\u00e7aise<\/i>), knowledge of French, stable livelihood and insertion (insertion professionnelle<\/i>), and good character (bonnes vie et m\u0153urs<\/i>). Each has refused real British and other Anglophone files, and each is documented in both statute and recent case law.<\/p>\n Assimilation is the broadest filter. Article 21-24 of the Civil Code<\/a> opens with the sentence that governs everything: “Nul ne peut \u00eatre naturalis\u00e9 s’il ne justifie de son assimilation \u00e0 la communaut\u00e9 fran\u00e7aise, notamment par une connaissance suffisante, selon sa condition, de la langue, de l’histoire, de la culture et de la soci\u00e9t\u00e9 fran\u00e7aises” The same article then details what assimilation means today: sufficient knowledge of the French language, history, culture and society, knowledge of the rights and duties of French nationality, and adherence to the essential principles and values of the Republic, with the language level and assessment method fixed by decree in the Council of State (Conseil d’\u00c9tat<\/i>, France’s supreme administrative court and legal adviser to the Government). In practice the prefecture tests assimilation twice: a civic examination on history, values and institutions, and a personal interview (entretien d’assimilation<\/i>) at the prefecture conducted in French. The interview report is the single most quoted document when files are refused. Prepare for it as an examination, not a chat: know the Republic’s symbols and principles, the meaning of la\u00efcit\u00e9<\/i> (secularism in public life), the organisation of the State, and be ready to explain in French why you want to become French and how you live in France day to day. The Conseil d’\u00c9tat controls these refusals strictly, and the control cuts both ways. On 29 May 2026 the Court annulled a Prime Ministerial opposition to a Moroccan spouse’s marriage declaration, holding: “Il ne ressort pas des \u00e9l\u00e9ments vers\u00e9s au dossier par le ministre de l’int\u00e9rieur, en particulier du rapport de synth\u00e8se du 26 septembre 2022 des services de la pr\u00e9fecture de l’Oise charg\u00e9s de l’instruction du dossier et du compte-rendu d’entretien compl\u00e9mentaire du 13 mai 2024, que Mme A… adopte un comportement ou soutient des th\u00e8ses manifestant un rejet des principes essentiels de la R\u00e9publique ou se tient d\u00e9lib\u00e9r\u00e9ment \u00e0 l’\u00e9cart de la communaut\u00e9 nationale.” (Conseil d’\u00c9tat, 29 May 2026, No 501856<\/a>). The lesson for British applicants is precise: the administration must evidence the lack of assimilation from the interview reports and the file, and a bare assertion is annulled \u2014 but a report that records concrete refusals of republican values, deliberate isolation from French life, or an inability to converse will be upheld.<\/p>\n Language is now the most mechanical cause of adjournment. The level is set by decree and currently sits at oral and written B1 of the Common European Framework for most applicants, with B2 increasingly discussed in reform proposals \u2014 so check the decree in force on your filing date and file the required diploma or approved test certificate (dipl\u00f4me ou attestation<\/i>) rather than relying on “I speak French at home.” Exemptions are narrow: age, disability certified by a doctor, and the French-schooled cases of Article 21-20. A British applicant who has lived ten years in the Dordogne speaking only English at the pub, with French limited to shopping, fails this filter as surely as any other nationality. Take an approved course, sit the approved test, and keep the certificate current for the file.<\/p>\n Livelihood and professional insertion form the third filter, and the courts give the administration very wide latitude here. The Court of Appeal of Nantes (cour administrative d’appel de Nantes<\/i>), confirming an adjournment, recalled the governing principle in these terms: “L’autorit\u00e9 administrative dispose, en mati\u00e8re de naturalisation ou de r\u00e9int\u00e9gration dans la nationalit\u00e9 fran\u00e7aise, d’un large pouvoir d’appr\u00e9ciation.” (CAA Nantes, 22 July 2026, No 25NT03094<\/a>). In that case the Minister had adjourned for two years because the applicant had not fully realised her professional insertion given the nature of her employment contract, while still considering her career since arrival \u2014 and the court upheld that reasoning as within the wide discretion. Transpose that to a British file: short-term contracts only, prolonged unemployment without resources, self-employment that never earns, or income so low that you depend on benefits will support an adjournment even after twenty years of residence \u2014 indeed that applicant had lived in France since 1989 with French children and French diplomas. The prefecture is not asking whether you survive; it is asking whether your economic life is durably anchored in France. Salaried applicants should show stable contracts and progression; the self-employed should show filed accounts, tax paid and a viable activity; early retirees and the financially independent should show durable, lawful resources and full tax compliance rather than a single large bank balance.<\/p>\n Good character is the fourth filter and the least forgiving. Article 21-23 of the Civil Code<\/a> states: “Nul ne peut \u00eatre naturalis\u00e9 s’il n’est pas de bonnes vie et moeurs ou s’il a fait l’objet de l’une des condamnations vis\u00e9es \u00e0 l’article 21-27 du pr\u00e9sent code.” The cross-referenced Article 21-27<\/a> excludes, among others, anyone sentenced to six months’ imprisonment or more without suspension, anyone convicted of offences against the fundamental interests of the Nation or terrorism, and anyone under an unlifted expulsion order or unexecuted ban from French territory. Unpaid taxes, repeated driving disqualifications, domestic-violence convictions and fraud sentences all feed this assessment, and the administration consults the criminal record (casier judiciaire<\/i>) systematically. The filter does not stop at the decree’s signature. On 26 November 2024 the Conseil d’\u00c9tat upheld the withdrawal of a 2021 naturalisation from a man convicted in February 2022 to fifteen months’ imprisonment, twelve suspended, for violence and harassment against his wife, on the ground that he could not be regarded as satisfying the good-character condition: the decree of 10 August 2023 withdrawing nationality was held lawful under Article 27-2 of the Civil Code<\/a>, which provides that “Les d\u00e9crets portant acquisition, naturalisation ou r\u00e9int\u00e9gration peuvent \u00eatre rapport\u00e9s sur avis conforme du Conseil d’Etat dans le d\u00e9lai de deux ans \u00e0 compter de leur publication au Journal officiel si le requ\u00e9rant ne satisfait pas aux conditions l\u00e9gales ; si la d\u00e9cision a \u00e9t\u00e9 obtenue par mensonge ou fraude, ces d\u00e9crets peuvent \u00eatre rapport\u00e9s dans le d\u00e9lai de deux ans \u00e0 partir de la d\u00e9couverte de la fraude.” (Conseil d’\u00c9tat, 26 November 2024, No 492338<\/a>). For British readers the message is stark: a conviction after naturalisation can still undo it within two years, and fraud in the file extends that window from discovery. Declare everything, pay what you owe, and do not file while criminal proceedings are pending without advice.<\/p>\n One reassurance belongs here before procedure. Naturalisation does not cost you your British citizenship. The United Kingdom expressly permits it: that dual citizenship is allowed in the United Kingdom, so a British citizen may also become a citizen of another country and keep British citizenship (GOV.UK, Dual citizenship<\/a>). France likewise permits dual nationality for Britons, with no renunciation requirement. You will travel with two passports, vote in each country where entitled, and remain fully taxable as before \u2014 nationality changes your passport, not your tax residence. Children minor at the time of your decree can acquire with you under the effet collectif<\/i> (collective effect) if they live with you in France and your names are on the decree, so list them in the application rather than assuming they follow automatically.<\/p>\n Files are lodged with the prefecture of your home address, now overwhelmingly through the online portal, which issues a receipt (r\u00e9c\u00e9piss\u00e9<\/i>) once the file is complete. That receipt starts the legal clock: Article 21-25-1 of the Civil Code<\/a> provides that “La r\u00e9ponse de l’autorit\u00e9 publique \u00e0 une demande d’acquisition de la nationalit\u00e9 fran\u00e7aise par naturalisation doit intervenir au plus tard dix-huit mois \u00e0 compter de la remise de toutes les pi\u00e8ces n\u00e9cessaires \u00e0 la constitution d’un dossier complet contre laquelle un r\u00e9c\u00e9piss\u00e9 est d\u00e9livr\u00e9 imm\u00e9diatement.” The English service-public.fr page confirms the same rule for applicants: a maximum of 18 months from the issue of the receipt to answer an application for naturalisation or reintegration The period falls to twelve months if you prove ten years of habitual residence at the receipt date, and it can be extended once by three months on a reasoned decision (service-public.fr, Naturalisation fran\u00e7aise par d\u00e9cret<\/a>). Silence is not consent: if no answer comes, chase the file in writing and keep proof, because the remedy clock runs from the express decision, and an implied refusal must be evidenced before the judge.<\/p>\n The examination has three stages. First the prefecture checks completeness and admissibility (recevabilit\u00e9<\/i>): age, lawful residence, permits, criminal record extract, civil-status documents with apostille and sworn translation where needed \u2014 British birth and marriage certificates must be legalised for French use and translated by a sworn translator (traducteur asserment\u00e9<\/i>) \u2014 tax notices, proof of resources and the language certificate. British documents deserve care: order full birth certificates, not short ones, and allow weeks for the apostille (apostille<\/i>, the Hague Convention stamp that authenticates a foreign public document). Second comes the assimilation interview plus the civic test, recorded in the report that will make or break assimilation challenges. Third, the prefect either forwards the file with a favourable proposal to the Minister for Naturalisations (ministre charg\u00e9 des naturalisations<\/i>), who grants or refuses, or the prefect refuses directly by a reasoned decision of inadmissibility, rejection or adjournment. Understand the vocabulary because the remedy is the same but the reasoning differs: inadmissibility says a legal condition is missing (residence, regularity, completeness); rejection says naturalisation is inopportune on the merits (insertion, assimilation, character); adjournment (ajournement<\/i>) postpones and sets a delay or conditions, classically two years to stabilise work or complete language, after which you must file again \u2014 the adjourned file is not kept warm. The decree of 30 December 1993 governing procedure states the Minister’s power in exactly these terms, as quoted by the Nantes court: that where the minister responsible for naturalisations considers that naturalisation or reintegration should not be granted, he rejects the application, and that he may instead adjourn it subject to a time limit or conditions File a fresh, strengthened application when the delay expires; a new request sent before the period ends may simply be dismissed.<\/p>\n British spouses of French citizens should measure the marriage route before joining the decree queue. Article 21-2 of the Civil Code<\/a> provides: “L’\u00e9tranger ou apatride qui contracte mariage avec un conjoint de nationalit\u00e9 fran\u00e7aise peut, apr\u00e8s un d\u00e9lai de quatre ans \u00e0 compter du mariage, acqu\u00e9rir la nationalit\u00e9 fran\u00e7aise par d\u00e9claration \u00e0 condition qu’\u00e0 la date de cette d\u00e9claration la communaut\u00e9 de vie tant affective que mat\u00e9rielle n’ait pas cess\u00e9 entre les \u00e9poux depuis le mariage et que le conjoint fran\u00e7ais ait conserv\u00e9 sa nationalit\u00e9.” The community-of-life period rises to five years where the foreign spouse cannot prove three years of uninterrupted regular residence in France since the marriage or cannot prove the French spouse was registered abroad \u2014 a frequent British configuration where the couple lived in London after the wedding. The declaration is made to the prefecture, a receipt issues, and the Government then has two years to oppose by decree in the Council of State for indignity or non-linguistic lack of assimilation: Article 21-4 of the Civil Code<\/a> states that “Le Gouvernement peut s’opposer par d\u00e9cret en Conseil d’Etat, pour indignit\u00e9 ou d\u00e9faut d’assimilation, autre que linguistique, \u00e0 l’acquisition de la nationalit\u00e9 fran\u00e7aise par le conjoint \u00e9tranger dans un d\u00e9lai de deux ans \u00e0 compter de la date du r\u00e9c\u00e9piss\u00e9 pr\u00e9vu au deuxi\u00e8me alin\u00e9a de l’article 26 ou, si l’enregistrement a \u00e9t\u00e9 refus\u00e9, \u00e0 compter du jour o\u00f9 la d\u00e9cision judiciaire admettant la r\u00e9gularit\u00e9 de la d\u00e9claration est pass\u00e9e en force de chose jug\u00e9e.” Without opposition in that period, nationality is acquired and recorded. The 29 May 2026 annulment quoted above shows the control is real: opposition for defective assimilation must be evidenced, not asserted. Note the trap in the other direction: separation, divorce proceedings or a break in shared life before the declaration defeats it, and a declaration signed while the couple already live apart is refused. Couples in difficulty should take advice on timing rather than filing a declaration the prefecture’s enquiry will describe as a separated household.<\/p>\n Paris and \u00cele-de-France add practical texture. Files from the capital region are examined by the prefectures of Paris, Hauts-de-Seine, Seine-Saint-Denis, Val-de-Marne, Essonne, Yvelines, Val-d’Oise and Seine-et-Marne, each with its own backlog and interview scheduling; Paris-region interviews are frequently several months after the receipt, and applicants should keep every document updated for the interview date, not just the filing date \u2014 fresh tax notice, current permit, recent pay slips. Bring originals plus copies, answer in French even if the agent offers English, and correct any error in the interview report on the spot or immediately afterwards in writing. Keep copies of everything lodged online: portal confirmations, the receipt, and every message, because the remedy judge in Nantes will reconstruct timeliness from your papers if the administration’s file is silent.<\/p>\nI. Can a British Citizen Be Naturalised? Residence, Assimilation and Good Character After Brexit<\/h2>\n
A. Five Years of Habitual, Lawful and Centred Residence in France<\/h3>\n
B. Assimilation, French Language, Livelihood and Good Character: the Four Filters That Refuse British Files<\/h3>\n
II. Filing, Deadlines and Remedies: Getting the Decree and Challenging Every Refusal<\/h2>\n
A. Where and How to File, the Interview, the 18-Month Clock and the Marriage Shortcut<\/h3>\n
B. Refused, Adjourned or Opposed: the Two-Month Hierarchical Appeal and the Nantes Judge<\/h3>\n