Moving from the United Kingdom to France does not make a share portfolio disappear from the tax map. The important questions are usually more precise: on what date did French tax residence begin, where was the seller resident when the contract was completed, what kind of shares were sold, and can the former country of residence still apply a temporary non-residence rule? The fact that a broker is in London, that the account is in pounds, or that the shares are held through a UK platform does not answer those questions by itself.

For a British citizen who has settled in France after Brexit, an ordinary disposal of shares will normally require a coordinated review of French residence, the France–UK double-tax treaty, French reporting forms and any remaining UK filing duty. The result can be different for shares deriving their value mainly from French land, for employee options, for a person returning to the UK after a short absence, or for a person who left France with substantial unrealised gains. This guide separates those situations, explains the evidence that should be kept, and gives a practical route through the French declaration process. It is designed for a private investor, not for the purchase of French property or the creation of a company.

I. Which country can tax UK shares after your move to France?

A. When France becomes your tax residence, the broker’s location does not decide the answer

The starting point is residence, not the nationality of the broker. French domestic law distinguishes a person whose tax domicile is in France from a person whose domicile is outside France. Article 4 A of the French Tax Code (Code général des impôts, or 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.” In plain English, a person resident in France is generally assessed on worldwide income, subject to treaty rules and the special regimes that apply to particular items. The same provision limits a non-resident to French-source income. Read the official wording in Article 4 A CGI.

French residence is fact-sensitive. A permanent home, the place where a family lives, the ordinary place of work, and the centre of financial interests can all matter. A British homeowner who spends time in France but keeps a UK home is not automatically non-resident in France; equally, a person who rents a French home and moves their family, work and daily life there should not assume that a UK bank account preserves UK residence. The domestic tests are then subject to the tie-breaker provisions of the treaty if both states regard the person as resident under their internal rules.

The treaty’s residence article uses concepts such as a permanent home, the centre of vital interests, habitual abode and nationality. It is therefore useful to assemble a dated residence file rather than rely on an assertion that the move happened “around the summer”. Keep the French lease or completion statement, utility records, school or medical registrations, travel history, employment or business evidence, banking changes, and the date on which the household actually moved. If the portfolio was sold close to the move, the timeline should show when the sale was agreed, when ownership passed, when the broker executed the order and when the proceeds became available. A trade entered before a move but settled afterwards can require careful contractual analysis.

The French tax return follows the same logic. A UK broker does not send a British taxpayer’s share gain directly into the French return in the way a French bank may pre-fill some figures. The taxpayer must gather the broker’s annual statement, transaction ledger, fees, corporate-action records and sterling values, then determine which French forms apply. Foreign-source status is not a reason to leave the gain out. Article 170 CGI requires a taxable person to file a detailed income declaration; its official text is available in the income declaration provisions of the CGI.

The calculation also does not begin with the cash balance shown by the platform. Article 150-0 A CGI brings gains from disposals of securities and equivalent rights within French income tax. The statutory wording covers “les gains nets retirés des cessions à titre onéreux” of securities and related rights. See Article 150-0 A CGI. Article 150-0 D then defines the net gain by comparing the effective disposal price, after seller-paid costs and taxes, with the effective acquisition price, subject to the statutory adjustments. See Article 150-0 D CGI.

That framework creates several practical traps for a British owner:

• A portfolio report in pounds is not a French tax calculation. Each relevant acquisition and disposal may need a euro value using a defensible exchange rate at the relevant date.
• A transfer between two accounts owned by the same person is usually not the same event as a disposal to a third party, but a change of broker or an in-kind transfer should be documented so that it is not mistaken for a sale.
• Reinvesting the proceeds does not normally defer French tax on an ordinary private share gain. The taxable event is generally the disposal, not the later decision to buy another security.
• A loss can matter even when no tax is payable on a gain in the same year. It must be calculated and reported correctly if it is to be used under the French carry-forward rules.
• Shares held in a UK ISA are still assets held by a French resident. The UK wrapper does not automatically create a matching French tax exemption; the French treatment of the underlying income and gain must be reviewed separately. The practical distinction between ISA treatment and ordinary securities should be kept with the portfolio records.

The French tax rate is also a moving part. The official French tax administration page on disposals of movable assets explains the ordinary private-investor regime, the flat-tax option and the alternative progressive-rate election. The current 2026 information published by the administration describes a standard overall rate of 31.4% for many ordinary securities gains, made up of income tax and social levies, but the exact result can change with the tax year, the taxpayer’s social-security position, the type of security, available losses and an election for the progressive scale. Consult the French tax administration’s page on movable disposals and do not copy a rate from an old broker statement.

The United Kingdom may still have a role, but it is not established merely because the shares were bought through a UK broker. The GOV.UK guidance on selling shares explains the UK domestic reporting framework, annual exempt amounts and payment mechanics. A person who is resident in France must then test that domestic position against the treaty and any special UK rule, including temporary non-residence. If the UK return reports a gain that the treaty assigns to France, the answer is usually not to pay twice; it is to analyse residence, the treaty article, the UK charge and the relief mechanism in the correct order.

The date of residence should therefore be treated as a legal finding supported by evidence. It should not be inferred from the date a French tax number arrived, the date an estate agent handed over keys, or the date a broker changed an address. Those facts can be relevant, but none is conclusive in every case. A clear chronology is the first protection against a tax authority treating the move as later, earlier or temporary than the family understood.

B. How Article 14 of the France–UK treaty separates ordinary shares, property-rich shares and former residents

The France–UK tax treaty is central for a British resident in France who sells shares. The treaty currently published by the UK government is available in the GOV.UK France tax-treaty collection, while the French implementing decree and treaty text appear in Decree no. 2010-20 on Légifrance. Article 14 is the capital-gains provision. It does not put every asset into one bucket.

First, gains from French immovable property are treated differently from gains on an ordinary portfolio. The state in which the land or building is situated generally retains taxing rights. The same treaty article addresses shares or comparable rights that derive more than a stated proportion of their value from immovable property. A share in a property-rich company may therefore need a different analysis from a listed company whose business merely owns an office or factory as part of its wider operation. The balance sheet, the relevant valuation date and the treaty wording must be checked rather than assuming that every company with French premises is “property-rich”.

Second, Article 14 paragraph 5 contains the ordinary rule for other assets. The official French text says: “Les gains provenant de l’aliénation de tous biens autres que ceux qui sont visés aux paragraphes 1, 2, 3 et 4 ne sont imposables que dans l’Etat contractant dont le cédant est un résident.” In translation, gains on assets outside the earlier categories are generally taxable only in the state of which the seller is resident. For an ordinary listed share disposal by a person who is resident in France at the relevant time, that points towards France, not the UK, even where the company is British and the broker is British.

Third, paragraph 6 preserves a limited former-resident rule. It says: “Les dispositions du paragraphe 5 n’affectent pas le droit d’un Etat contractant de prélever, conformément à sa législation, un impôt sur les gains tirés de l’aliénation de tout bien par une personne qui est, et qui a été à un moment quelconque pendant les six années fiscales précédentes, un résident de cet Etat contractant ou par une personne qui est un résident de cet Etat contractant à un moment quelconque de l’année fiscale au cours de laquelle le bien est aliéné.” The six-year language is important, but it is not a universal power to tax every gain after Brexit. The domestic charge must exist, the treaty conditions must be met, and the facts must fit the particular asset and year.

The wording is especially relevant when someone leaves the UK, becomes resident in France and sells shares during the following years. The UK temporary non-residence regime can also interact with a return to the UK. HMRC’s current HS278 guidance for 2026 describes the conditions under which certain gains made while temporarily non-resident can be brought into a later UK assessment. The rule has detailed residence-history and absence-period conditions. A person planning a return should not treat a short stay in France as a clean separation for UK capital-gains purposes without testing those conditions.

French exit tax is a separate issue. It concerns certain unrealised gains when a person who has been French tax resident transfers their domicile out of France. Article 167 bis CGI refers to taxpayers resident in France for at least six of the ten years before the transfer and includes thresholds and conditions for significant holdings. The statutory provisions, including payment deferral rules, are set out in Article 167 bis CGI. It usually concerns a person leaving France, not a British person making an ordinary disposal after first arriving in France. Still, it can matter later if that person moves back to the UK with a substantial portfolio.

The Conseil d’État, France’s highest administrative court, has repeatedly treated residence and treaty allocation as fact-driven. In decision no. 357576 of 29 April 2013, available on Légifrance, it examined the French exit-tax regime and held, in substance, that the regime did not by itself prevent a person from leaving France. That decision is not a shortcut for a British share sale, but it shows why exit-tax analysis and ordinary disposal analysis must not be conflated.

In decision no. 442790 of 25 June 2021, the Conseil d’État considered the centre of economic interests and referred to a person’s financial interests, including property and securities. The official decision is CE, 25 June 2021, no. 442790. Its value for a British newcomer is practical: a portfolio can contribute to the residence analysis, but its existence alone does not prove that France is or is not the centre of the person’s life. The court looks at the overall pattern.

There are also treaty cases involving the United Kingdom that illustrate the need to classify the asset correctly. In decision no. 408763 of 18 October 2017, the Conseil d’État considered gains linked to employee stock options for a person resident in the UK. It held that the gain was taxable in France only to the extent that the activity remunerated by the option grant had been carried on in France. See CE, 18 October 2017, no. 408763. That is not a ruling that an ordinary share gain is apportioned by the employee’s workdays. It is a warning that options, employment remuneration and ordinary investment shares belong to different legal analyses.

Decision no. 360352 of 19 July 2016, also concerning the France–UK treaty, addressed a deferred gain connected with an exchange of securities and the timing of a later disposal. The decision is available at CE, 19 July 2016, no. 360352. It demonstrates that a later sale does not necessarily erase the tax consequences of an earlier transaction when France had taxing competence at the relevant stage. The details of that case should not be transplanted mechanically to a modern portfolio, but the timing lesson is valuable.

Finally, a treaty allocation does not replace domestic reporting. The treaty determines which state may tax and how double taxation is relieved; it does not prepare the French forms or prove the residence date. Article 24 provides the mechanism for eliminating double taxation in the relevant circumstances. If both countries have collected tax, preserve both assessments and calculate the credit or repayment route rather than simply netting the figures informally. The French convention text and its relief article are in the same Légifrance treaty publication.

The correct classification can be summarised as follows: ordinary shares are normally tested under the residence rule; shares deriving their value from French immovable property may be tested under the property rule; employee options require an employment-reward analysis; and a person who has recently left or returned to a country must check the former-resident rules. That is why the answer “the broker is British” is too short to be reliable.

II. How should you calculate, report and challenge the tax?

A. How to calculate the gain, convert sterling and complete the French forms

The safest process begins with a transaction ledger, not a tax-rate calculator. Ask the broker for a complete history covering every acquisition, disposal, transfer, stock split, merger, dividend reinvestment, rights issue and fee. A year-end statement may show the value of the portfolio but not the historic acquisition lots required to calculate a French gain. If the broker uses average cost, FIFO or another method for UK purposes, do not assume that its presentation is automatically the method required for France.

For each disposal, record the security identifier, number of units, order date, execution date, settlement date, gross proceeds, fees, withholding, acquisition lots, acquisition costs and any corporate action. Record whether the asset was an ordinary listed share, an option, a fund unit, an employment award, a property-rich holding or an interest in a closely held company. The legal classification affects both the treaty and the French form.

The French domestic calculation starts with the effective disposal price and acquisition price. Article 150-0 D CGI describes the gain as the difference between the disposal price net of costs and taxes paid by the seller and the acquisition price, with statutory adjustments. A translated summary is useful for working papers, but the controlling text remains the official Article 150-0 D provision. Keep the fee invoice that supports every deduction. Do not deduct an amount merely because the broker labels it “commission” if it relates to custody or an unrelated service.

Sterling-to-euro conversion requires a consistent method. A taxpayer should record the exchange-rate source, the date used and the reason for using it. The economically intuitive method is to convert each acquisition and disposal at a rate appropriate to that transaction, rather than converting the annual net cash profit at year-end. A broker’s own currency conversion can be evidence, particularly where the statement shows the rate and fee, but a third-party rate may be needed where the broker reports only pounds. Retain both the original sterling figures and the euro working.

Foreign exchange can change the result. A share bought for £10,000 when the pound was strong and sold for £12,000 after sterling weakened can produce a different euro gain from the £2,000 headline profit. Conversely, a smaller sterling gain can become a larger euro gain. This is why the French file should not simply reproduce the UK capital-gains computation. If a UK return has already been filed, reconcile its method with the French calculation and explain every difference.

The French tax administration’s page on share disposals explains that the total of gains and losses is reported through the income-tax return, with form 2074 used in situations requiring detailed calculation. The administration’s official page for form 2074 provides the current instructions and document. Where a bank or broker has calculated the figures in a form accepted by the French administration, a taxpayer may in some circumstances transfer the totals rather than complete every schedule, but a foreign broker’s report does not automatically satisfy that condition. The page addressing shares and declarations is available at the official French tax FAQ on share sales.

Form 2042-C may be needed to carry the relevant totals into the main income-tax return. The exact boxes depend on the year, the type of transaction, the use of form 2074 and whether losses are carried forward. Use the instructions for the relevant tax year rather than an old screenshot. If a UK ISA, pension wrapper, investment fund or employee scheme is involved, determine whether the underlying transaction belongs in the same category before entering a figure.

The account itself can create a second filing obligation. Article 1649 A CGI requires French residents to declare the references of accounts opened, held, used or closed abroad at the same time as the income declaration. The official text is at Article 1649 A CGI. A UK brokerage account may fall within the foreign-account rules depending on its legal operation and the way the institution makes the account available. A securities account and a bank cash account should be inventoried separately. Do not assume that declaring the share gain also declares the account.

A practical French filing pack should contain:

1. The residence chronology, including the date France became the centre of the person’s daily life and any treaty tie-breaker analysis.
2. The broker’s full transaction history, annual tax statement and fee schedule.
3. A euro-conversion table for each acquisition and disposal, with the source and date of every rate.
4. A lot-matching schedule explaining inherited shares, gifts, reorganisations, splits, reinvested distributions and transfers.
5. The French forms actually filed, the submission receipt and the calculation behind every total.
6. The UK return, payment confirmation or HMRC correspondence if the UK has asserted a charge.

If a gain is large, seek a review before filing rather than after an automated assessment. A filing that omits the gain can create interest, penalties and an avoidable credibility problem. A filing that reports the gain twice can create a cash-flow problem and then require a treaty claim. The best time to resolve a classification issue is before the return becomes the only record of what happened.

The year of sale also matters. Tax rates, social levies, annual allowances and forms change. The 2026 French page on movable disposals should be checked alongside the year-specific return instructions. Where the taxpayer is affiliated to the UK social-security system under a coordination rule, the social-levy analysis may differ from the headline private-investor rate; that point should be evidenced rather than assumed from nationality.

The UK side should be kept parallel. HMRC’s rates and allowances guidance is updated by tax year. If the person is non-resident in the UK, the domestic charge may be limited, but temporary non-residence or a special asset category can change that conclusion. If a UK return is not required, preserve the residence evidence and treaty analysis anyway. The absence of a UK filing does not prove that the French calculation is right, and a French filing does not prove that HMRC has accepted the treaty position.

The calculations should be readable by someone who did not make the trades. A table with one line per disposal, a separate table for losses, and a short note on the treaty classification are more persuasive than a single spreadsheet total. If the broker’s statement cannot identify the acquisition lots, request a corrected statement or reconstruct the lots from contract notes. Do not silently replace missing data with an estimate when the amount is material.

B. What evidence protects you in a residence dispute, double-tax case or HMRC challenge?

Evidence is not an administrative afterthought. In a dispute, the tax authority may ask not only “how much was the gain?” but also “where were you resident, when did the disposal happen, and why does the treaty article apply?” The file should answer those questions in chronological order.

Start with residence. Build a calendar for the tax year showing nights and working days in France, the UK and elsewhere. Add the household’s permanent homes, travel bookings, utility consumption, insurance, school arrangements, medical appointments, vehicle records and correspondence with tax authorities. A calendar is not conclusive, but it helps connect the documents. If the person maintained two homes, explain which one was available for permanent use and where the family actually lived. If the person worked remotely for a UK employer, keep the employment agreement, payroll records and evidence of where duties were performed; employment income and share gains must not be confused.

Next, record the treaty tie-breaker analysis. The France–UK convention’s residence rules should be read with the domestic tests in both states. The treaty does not ask only where a passport was issued. It looks at the quality of the home, personal and economic relations and habitual living pattern. If both countries issued residence certificates, keep both and explain how the conflict was resolved. If one country never issued a certificate, do not treat silence as a ruling; use the factual record.

Then prove the legal identity of the asset. Keep the prospectus or issuer description for a fund, the articles or annual report where a company may be property-rich, the option plan for an employee award and the account terms for an ISA. A listed UK company with a French subsidiary is not automatically a share deriving its value from French land. Conversely, a holding company whose principal asset is French property may trigger the treaty’s immovable-property rule. The valuation and ownership chain should be available if that issue is plausible.

The French court decisions provide useful warnings about facts and timing. In CE decision no. 389198 of 27 March 2017, the court considered Article 4 A and the evidence relevant to French residence; the official record is CE, 27 March 2017, no. 389198. In CE decision no. 421612 of 26 July 2018, the court addressed the interaction between French taxation and a foreign state’s taxation and refused to treat every difference as a breach requiring France to neutralise the other country’s tax; see CE, 26 July 2018, no. 421612. These decisions do not decide a British investor’s file, but they show why a general fairness argument is weaker than a documented residence and treaty argument.

If both countries tax the same disposal, identify the legal route before paying or claiming. The treaty may allocate the gain exclusively to one state, or it may permit one state to tax with a credit in the other. The credit mechanism can depend on the character of the income, the tax actually paid, the assessment year and the documentary proof. A UK payment receipt is not enough if it does not identify the gain; a French assessment is not enough if it includes several income categories. Preserve the computation, assessment, payment date and exchange rate used for the credit claim.

Communications with the UK broker deserve special care. Ask for confirmations in a format that shows the original currency, security identifier, number of shares and execution date. Download statements before changing the address or closing the account. If the platform reports a “cost basis” calculated under UK rules, label it as such and reconcile it to the French schedule. For inherited or gifted shares, obtain the probate valuation, gift documentation and historic acquisition evidence. For employee shares or options, keep the grant, vesting, exercise and sale dates together.

The six-year language in Article 14 paragraph 6 means that a departure from the UK should be documented even if no immediate sale occurs. Keep the final UK residence evidence, the date the French residence began, the portfolio value at the move and all disposals during the following years. If the person returns to the UK, preserve the French departure evidence and the unrealised portfolio value at that date. The same file can become important under the UK temporary non-residence rules, which are based on detailed residence history and the duration of the absence.

A person who moved to France after Brexit should also distinguish legal status from tax status. A residence permit, visa, settled status, national-insurance record or French social-security number can support the chronology, but none automatically decides where a capital gain is taxable. The portfolio evidence, treaty residence and disposal date remain central. For broader residence and first-return questions, the site’s guide to the first French tax return after moving from the UK can be read alongside this narrower share-gain analysis.

Before answering an information request, prepare a short chronology and a schedule of disputed points. If the authority asks why France is entitled to tax, point to the residence facts and Article 14. If it asks why the UK is not entitled, identify the ordinary-share rule and test paragraph 6. If it asks for the amount, provide the lot-by-lot euro calculation. If it asks about the account, provide the foreign-account analysis under Article 1649 A. A targeted response is easier to verify than a large unindexed upload.

Deadlines must be treated as live. French income returns, correction periods, requests for information and claims for relief have different time limits. HMRC deadlines differ again. Use the date on the assessment or request, not the date on which the letter was opened, and keep proof of electronic submission. If a payment is due while the treaty position is being challenged, consider the consequences of paying under protest, requesting a suspension or seeking a repayment; do not ignore the assessment while waiting for an adviser’s informal view.

The strongest challenge file usually contains four layers: facts, calculations, treaty text and correspondence. The facts prove residence and asset identity. The calculations prove the amount. The treaty and domestic provisions prove the allocation. The correspondence proves what was disclosed and how the authorities responded. This layered approach is more durable than citing a blog post or relying on the broker’s label.

The same principle applies to a voluntary correction. If a previous French return omitted a UK share disposal, identify the year, reconstruct the calculation, calculate any interest and penalty exposure, and make a coherent disclosure. If the gain was reported in France but also taxed in the UK, do not file a second unexplained amendment. Explain the treaty position and attach the documents needed for the relief route. A correction should make the file clearer, not create a new contradiction.

Conclusion

For a British person settled in France, UK shares are usually analysed through four questions: where was the seller treaty-resident at the time of disposal, what kind of asset was sold, does a former-resident or temporary-non-residence rule apply, and what evidence supports the euro calculation? An ordinary portfolio disposal is not decided by the broker’s address or by the currency of the account. The France–UK treaty, French Articles 4 A, 150-0 A, 150-0 D, 1649 A and, where relevant, 167 bis, must be read with the facts of the move.

The practical next step is to freeze the records: download the complete broker history, create the residence calendar, preserve the acquisition evidence and separate ordinary shares from options, funds and property-rich holdings. Then prepare the French forms and any UK filing or treaty claim from the same reconciled schedule. If the amount is material, the sale occurred close to the move, or both states have issued assessments, obtain advice before submitting a correction or relying on a tax credit.