You did everything sensibly. You moved to France, became French tax resident after Brexit, and drew the quarter of your British defined-contribution pension pot that can be taken free of United Kingdom tax. Then the French tax office, the fisc, taxed the whole lump sum as a pension, added social charges on top, and your adviser told you there was nothing to be done. That advice is often wrong, but the opposite belief is wrong too: the lump sum is not tax-free in France simply because no British tax was charged. France taxes its residents on their worldwide income, the France-United Kingdom double tax treaty leaves private pensions to the country where you live, and the French Tax Code contains a specific regime for retirement benefits paid in capital form. Inside that regime sits a little-known option that can cut the income tax on a lump sum to a flat 7.5 percent after a 10 percent allowance, provided the payment arrives in one single transfer and your contribution history qualifies. Take the money in two instalments, and an administrative court of appeal has confirmed that the option is lost with no excuse accepted, even where the split was driven by foreign pension rules. This guide explains, for a British reader living in France, why the lump sum is taxable here, how the 7.5 percent flat levy and the quotient averaging mechanism work, what social charges apply, how to declare the payment, and how to reclaim British tax wrongly withheld and challenge a French assessment before the deadline expires.

I. Why France can tax the lump sum you thought was tax-free

A. How French tax residence makes your worldwide income taxable in France

French income tax starts with one blunt rule. Article 4 A of the French Tax Code provides: “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.” In plain English, once France is your tax home, known in French as your domicile fiscal, you are liable to French income tax on all of your income, wherever it comes from. A British pension lump sum paid in London, Manchester or Edinburgh is therefore inside the French tax net from the moment you are French tax resident. You can read the provision here: Article 4 A of the Code général des impôts.

Many British newcomers misunderstand how that residence is tested. There is no single 183-day rule that decides everything. Article 4 B of the same Code lists three alternative tests: “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”, alongside holding the centre of your economic interests in France, and meeting any one of them is enough: Article 4 B of the Code général des impôts. Your foyer means your family home, the place where your spouse and children habitually live; your séjour principal means the country where you spend most of your time; the professional-activity test catches remote workers who live in France while working for a British employer. If your family home is in the Dordogne, your children attend a French school and you spend eight months a year in France, you are French tax resident even if you keep a flat in London and spend 170 days in Britain. The calendar count matters mainly as evidence of where your main stay is, not as a standalone threshold that protects you below some magic number.

The year of the move needs care. French residence can begin on the day you settle, so a lump sum drawn in the same calendar year as your arrival may fall into French residence or into non-residence depending on the precise chronology. Someone who draws the lump sum in March while still living in Kent and moves to France in September is in a very different position from someone who moves in February and draws in October. Keep boarding passes, the removal company invoice, the French lease or completion deed, school enrolment letters and energy contracts: the tax office asks for this paper trail whenever the date of arrival is disputed, and a lump sum gives it a reason to ask. If you drew the money just before leaving Britain, take advice on which country had the taxing right at the exact payment date rather than assuming the later French return covers everything.
A second confusion concerns the double tax treaty. The treaty does not exempt your pension; it allocates the right to tax it. France and the United Kingdom signed a full income tax treaty in London, and the French tax authority’s published commentary records that France and the United Kingdom signed their current double tax treaty on income and capital gains in London on 19 June 2008. You can consult that commentary here: BOI-INT-CVB-GBR-10, the French commentary on the France-United Kingdom treaty. For private pensions paid for past employment, the settled treaty outcome is the one the same published doctrine states for pensions generally: Private pensions and similar payments for past employment are taxable only in the state where the recipient lives, which is the outcome the published French treaty doctrine states for this category. In other words, a French resident’s British private pension, including a lump sum that replaces pension rights, is taxable only in France, and Britain should give up its tax. That exclusivity is good news and bad news at once: it lets you reclaim British emergency tax or withholding, but it confirms that France is entitled to apply its own rules in full, including rates far above zero.

Two boundaries matter. First, the residence-state rule covers private employment pensions, personal pensions and self-invested personal pensions, the SIPP wrappers many British savers hold. It does not cover every payment with the word pension in it. British state retirement pensions, pensions paid under social security legislation, and pensions for former government service follow different treaty provisions with their own logic, and each needs separate analysis. Second, Brexit changed nothing in this treaty: the 2008 convention is bilateral and continues to apply exactly as before, and the Withdrawal Agreement protects residence and social security coordination, not income tax allocation. Anyone who tells you that Brexit moved pension taxation back to Britain, or that the treaty lapsed, is mistaken.

B. How French law turns a British tax-free lump sum into taxable pension income

French domestic law then does the taxing. Article 158 of the Tax Code, which defines the categories of taxable income, contains a special paragraph for retirement benefits paid in capital form: “Par exception au a et sous réserve de l’application du 6° bis de l’article 120 ou du II de l’article 163 bis, les prestations de retraite versées sous forme de capital, autres que celles qui sont exonérées en application du 4° bis de l’article 81” fall into a dedicated regime: Article 158, 5, b quinquies of the Code général des impôts. Your British lump sum is precisely a prestation de retraite versée sous forme de capital, a retirement benefit paid as a lump of capital rather than a monthly pension. Because it is not one of the narrow French statutory exemptions listed in Article 81, it is taxable in France even though Britain charged nothing. The British tax-free status is invisible to the French provision: France asks only whether the payment is a capital-form retirement benefit received by a French resident, and if the answer is yes, it taxes it.

The same paragraph then splits the lump sum into layers that many British taxpayers miss. For the part of the payment that corresponds to certain French-style deductible retirement savings, it provides that those amounts “Sont imposées sans application de l’abattement prévu au deuxième alinéa du a du présent 5” (Article 158, 5, b quinquies of the Code général des impôts), meaning the familiar 10 percent pension allowance does not apply to that slice. For the growth and product element attached to those savings, it sends the taxpayer to the flat-rate regimes of Article 200 A and Article 125 A. A British pension is not a French plan d’épargne retraite, the PER retirement savings plan, so the mapping is never mechanical: the tax office must characterise a foreign-law pension under French categories, and characterisation disputes are exactly where files are won or lost. What is certain is the default outcome if you do nothing: the lump sum joins your taxable income for the year and is charged at the progressive scale, where a large one-off payment can push a slice of your income into the 30, 41 or even 45 percent bands. Take a household that normally pays tax at 11 percent and draws the equivalent of 140,000 euros in one year: tens of thousands of euros of the lump sum can be taxed at 30 or 41 percent simply because the whole amount counts as one year’s income. That scale effect is why the planning options in Part II are worth more than any argument about the British treatment.

One practical consequence follows immediately. Because the treaty gives France the exclusive right to tax, any British tax deducted at source, through emergency code or otherwise, is in principle recoverable rather than creditable. Do not declare the British tax as a credit on your French return and move on; the French return has no British tax to credit where France taxes exclusively, and the remedy sits in Britain through a treaty reclaim. Keep every British document from the payment: the P45-style leaver statement, the pension scheme’s payslip showing the tax code applied, the bank credit advice with the payment date and the exchange rate. The payment date fixes the taxable year in France, the sterling-euro conversion fixes the taxable amount, and the British deduction paperwork founds the reclaim. Where the payer applied the wrong code and sent a third of your lump sum to HM Revenue and Customs, that paperwork is also the evidence your French lawyer uses to show the double charge is real and to sequence the two countries’ procedures correctly.

II. How to cut the bill and stay fully compliant

A. How to choose between the 7.5 percent flat levy and the quotient before you touch the money

French law offers an extraordinary way out, but only if you plan the payment before it lands. Article 163 bis, paragraph II, of the Tax Code provides: “Les prestations de retraite versées sous forme de capital imposables conformément au b quinquies du 5 de l’article 158 peuvent, sur demande expresse et irrévocable du bénéficiaire, être soumises à un prélèvement au taux de 7,5 % qui libère les revenus auxquels il s’applique de l’impôt sur le revenu. Ce prélèvement est assis sur le montant du capital diminué d’un abattement de 10 %.” Read it here: Article 163 bis, II, of the Code général des impôts. In English: on your express and irrevocable request, the lump sum can bear a discharge levy, a prélèvement libératoire, of 7.5 percent computed on the capital reduced by a 10 percent allowance, and that levy replaces income tax on the amount. A 100,000 euro qualifying lump sum therefore bears 6,750 euros of French income tax instead of whatever the progressive scale would have produced, which for a household already in the 30 percent band means a saving measured in tens of thousands. The request is made on the tax return for the payment year; express means ticked and written, irrevocable means you cannot try the scale first and switch later if the assessment disappoints.

The statute then states the two conditions that destroy most files: “Ce prélèvement est applicable lorsque le versement n’est pas fractionné et que le bénéficiaire justifie que les cotisations versées durant la phase de constitution des droits, y compris le cas échéant par l’employeur, étaient déductibles de son revenu imposable ou étaient afférentes à un revenu exonéré dans l’Etat auquel était attribué le droit d’imposer celui-ci.” (Article 163 bis, II, of the Code général des impôts) The payment must not be split, and the contributions that built the rights must have been deductible from taxable income or attached to exempt income in the state that had the right to tax them. For a British saver this second test usually turns on the contribution history: salary-sacrifice amounts, employer contributions relieved in Britain, and personal contributions that received tax relief at source or through self-assessment. Assemble that history before drawing, because the French office will ask for it and British schemes answer slowly: annual statements, P60s showing the relief mechanism, and the scheme rules describing the tax-free cash element. Where contributions were paid from already-taxed income with no relief, that slice of the analysis weakens, and the file must be structured around whichever portion genuinely qualifies rather than presented as an all-or-nothing gamble.

The single-payment condition deserves its own warning because it is brutally strict. The administrative court of appeal of Lyon, in a case about a Swiss retirement capital paid in two instalments, upheld the tax office’s refusal of the 7.5 percent levy and held that “le versement de l’avoir de vieillesse a été fractionné, notamment au sens des dispositions précitées du II de l’article 163 bis du code général des impôts, lesquelles ne prévoient pas d’exception dans l’hypothèse où le fractionnement proviendrait d’une cause extérieure à la volonté du contribuable”: CAA Lyon, 28 November 2024, No 22LY01728. The taxpayer had split the payment to protect a Swiss tax advantage on recent buybacks, yet the court answered that the taxpayer’s choice to draw early, when waiting three years would have allowed a single payment, meant the split was voluntary and the flat levy was lost for both instalments. Transpose that reasoning to a British saver who draws the tax-free cash in stages, takes an uncrystallised funds pension lump sum, the UFPLS route, across two tax years, or phases withdrawals to stay in a British allowance: each staging choice risks being read as a fractionnement that kills the 7.5 percent option for the whole operation. If the levy matters to you, draw once, in one transfer, in one year, and keep the scheme’s payment confirmation showing a single credit. Anyone whose scheme rules force staged payments should model the scale cost first and consider whether delaying French residence, or drawing before the move, changes the picture more cheaply than fighting a lost levy claim afterwards.

Where the flat levy is unavailable or unattractive, the fallback is the quotient, an averaging mechanism for exceptional income. Article 163-0 A of the Tax Code provides that for income which by nature cannot be collected yearly and exceeds the average of the last three years’ taxable income, “l’intéressé peut demander que l’impôt correspondant soit calculé en ajoutant le quart du revenu exceptionnel net à son revenu net global imposable et en multipliant par quatre la cotisation supplémentaire ainsi obtenue”: Article 163-0 A of the Code général des impôts. The mechanism taxes a quarter of the exceptional amount at your marginal profile and multiplies the extra charge by four, which softens the scale-shock of a one-off receipt without matching the flat levy. A pension lump sum that dwarfs your usual income is the textbook candidate, but the three-year average test and the exceptional-nature test must both be met, and the option must be requested properly. In practice the ranking is simple: a qualifying single payment takes the 7.5 percent levy; a split payment or a weak contribution history falls back to the quotient; an unplanned payment with neither option prepared pays the full scale. Run the three calculations side by side before the draw, not after the assessment arrives, because the levy request cannot be invented retrospectively once the return has gone in without it.

B. How to declare correctly, pay the right social charges and reclaim any British tax

Declaration comes first because errors here compound everywhere else. A French resident declares worldwide income on the French return, and a British lump sum belongs on the return for the calendar year of payment, converted into euros at a justifiable rate with the bank advice kept alongside. Report the gross amount and let the French computation do the work; never declare only the net after British withholding, and never omit the payment on the theory that Britain already taxed it. Tick the 7.5 percent option box for the capital pension and attach the express request where the form invites it, or claim the quotient expressly in the alternative, because neither benefit is automatic and an unclaimed option is treated as a choice of the scale. Our companion guide to British private pensions in France walks through the declaration and treaty-relief routine in detail: UK Private Pension in France After Brexit: How to Declare It, Recover UK Tax Withheld and Claim Treaty Relief. Where the payment straddles the arrival year, file consistently with the residence position you can evidence, and disclose the chronology rather than leaving the office to discover the transfer through automatic exchange of information, which it increasingly does.

Social charges, the CSG and CRDS levies that sit on top of income tax, are the second layer and the most commonly miscalculated. The base rule sits in the Social Security Code: persons fiscally domiciled in France are subject to the contribution on capital income assessed on the net amount used for income tax, and the provision lists the income families concerned: Article L. 136-6 of the Code de la sécurité sociale. The rate rule then states: “Sont assujetties à la contribution au taux de 8,3 % les pensions de retraite, et les pensions d’invalidité”: Article L. 136-8 of the Code de la sécurité sociale. A French resident’s pension income therefore normally carries the 8.3 percent charge plus the accompanying debt-repayment contribution, even where the 7.5 percent income-tax levy applied, because the levy replaces income tax, not social charges. The one genuine exit concerns health coverage: where you remain insured under the British system through a portable S1 healthcare certificate, so that France is not the state competent for your health cover, the French social charges linked to health coverage can be disputed on the assessment. That dispute is technical, document-heavy and time-limited, so raise it with the S1, the British coverage attestation and the assessment in hand rather than by simply not paying.

The courts have recently underlined how seriously the social-charge base is policed on foreign pensions. The Conseil d’État, ruling on a Swiss capital-form survivor’s pension received by a French resident, held that the coordination rules “n’interdisent pas à l’Etat membre compétent d’assoir les cotisations sur la totalité des pensions perçues de deux ou plusieurs Etats membres par une même personne”, meaning the competent state may assess charges on all the pensions a person draws from several states, not only the domestic one: Conseil d’État, 8th-3rd chambers combined, 25 October 2024, No 473997. The facts were Swiss rather than British, and the reasoning turns on European coordination instruments, but the signal for British files is clear: do not assume a foreign-source lump sum escapes the French social-charge base, and where you claim an S1-based exemption, frame it precisely around which state is competent for health cover rather than around where the money was paid. Conversely, the same decision confirms that the analysis is legal and checkable, which is exactly what a well-built challenge exploits.

That challenge has two fronts and one clock. In Britain, file the treaty reclaim for the tax wrongly withheld once France confirms, or the return demonstrates, French residence for the payment year; the treaty position is that the private pension was taxable only in France, so the British deduction should come back. In France, if the assessment applies the scale where the levy was requested, denies the quotient, or charges social levies despite a valid S1 position, file a formal claim, a réclamation, with the tax office that issued the bill. The admissibility deadline is strict: “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” of the collection or payment event: Article R*196-1 of the Livre des procédures fiscales. A 2026 assessment is therefore typically challengeable until 31 December 2028, but interest accrues and enforcement continues while you argue, so consider a payment deferral request alongside the claim. Send the claim by a traceable route, attach the payment proofs, the residence evidence, the contribution history and the S1 where relevant, and state each legal ground separately so that a partial admission remains possible even if the main ground fails.

Conclusion

A British pension lump sum drawn as a French resident is taxable in France, usually at the progressive scale unless you secured the 7.5 percent flat levy with a single payment and a qualifying contribution history, with the quotient as the fallback and social charges as the unavoidable second layer. The treaty protects you against genuine double taxation by assigning the pension to France, which means the practical fight is about the French rate and the French base, plus getting back whatever Britain withheld in error. Sequence the operation correctly: confirm your residence date, draw once, request the levy expressly, declare gross, verify the social charges against your health-cover position, and reclaim in Britain. And if the assessment has already landed, check the 31 December of the second following year before you assume the file is closed, because most of these cases are still winnable inside that window with the right documents.

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