If you have moved from the United Kingdom to France, or own a French home while remaining UK-resident, the practical problem can arrive before the tax analysis: France asks for a numéro fiscal, meaning a 13-digit French tax identification number, but you cannot create or access your online account. The account is called the espace Finances publiques, the secure online tax account used to view notices, send messages and complete many filings. A blocked account can leave a British owner unable to answer a tax notice, pay a bill or prove that a first return was sent.

Brexit did not create a separate tax number for British citizens. It changed the immigration and cross-border context in which the French tax administration assesses your file. You may be taxable in France without being French tax-resident, or tax-resident in France while still receiving UK income. The correct route therefore depends on your residence, the nature of the French tax due, whether a number has already been issued and whether this is your first declaration of income or assets in France. This guide, checked against the official sources available on 29 August 2026, gives a decision path for the account problem and the legal safeguards for a late or disputed return.

I. How can a British resident obtain a French tax number and unlock the online tax account?

A. Do I need a numéro fiscal if I only own a French property?

Yes, a British owner can need a French tax number even when the property is a second home, produces no rent and the owner remains resident in the UK. The number identifies the individual taxpayer. It is not a residence permit, it does not by itself make someone French tax-resident and it is not proof that French income tax is payable. It allows the administration to connect a person with local taxes, French-source income, a tax household and correspondence.

The first distinction is between the tax number and the underlying liability. A non-resident owner may receive a taxe foncière bill, meaning French property tax charged to the owner, or a taxe d’habitation bill, meaning the residence tax that can still apply to a furnished second home. A non-resident may also have French rental income, a French pension, a taxable capital gain or another French-source item. In those cases, the absence of French income tax liability does not mean that no taxpayer record should exist.

The second distinction is between French domestic residence and residence under the France–UK tax treaty. Article 4 B of the French General Tax Code identifies the French tax domicile through the home or principal stay, professional activity and economic interests, subject to an international treaty. The current text includes the words “Les personnes qui ont en France leur foyer ou le lieu de leur séjour principal”. That is a legal test, not a label attached to a British passport or a French address. Read the current Article 4 B of the French General Tax Code before describing yourself as resident or non-resident in a form.

The France–UK convention must then be applied if both countries treat you as resident under their domestic rules. The convention published by Decree no. 2010-20 of 7 January 2010 on Légifrance is the French official publication of the 2008 convention. The UK-side synthesised treaty text on GOV.UK gives the tie-breaker sequence: permanent home, closer personal and economic relations, habitual abode and nationality, with competent-authority agreement where necessary. The treaty definition also excludes a person who is taxable in a state only on income or gains from sources in that state. That is why a French property owner can have a French tax number and a French property tax bill without becoming treaty-resident in France.

Evidence matters more than the description used in an email. In CAA Paris, 18 June 2026, no. 23PA05246, the court examined family life, accommodation, professional work, expenditure and productive assets across France and the United Kingdom. It stated that, for the French domestic “home” test, “le foyer s’entend du lieu où le contribuable habite normalement et a le centre de ses intérêts familiaux”. The decision concerned a historic tax year and a property transaction, but its practical lesson is current: a London home, French accommodation, family arrangements and work evidence must be considered together.

An older decision shows why a UK tax document should be preserved rather than replaced by an assertion. In Conseil d’État, 14 February 1979, no. 06961, the court considered a British national with a pension and British tax. It referred to the lack of “tout document probant fourni par l’intéressé quant à sa situation de résident au regard de l’Income Tax”. That decision applied an earlier convention and must not be copied mechanically into a modern file, but the evidential point remains useful: nationality, a pension or tax paid in the UK does not replace documents proving treaty residence.

For a British owner, the practical consequence is straightforward. Request or recover the tax number so that the record can be corrected, but do not let the number decide the residence analysis. Keep separate folders for:

• the French property and its local-tax notices;
• French-source income and any withholding;
• days spent in France and in the UK;
• homes available to you, family location and professional activity;
• UK residence evidence, such as HMRC correspondence, council-tax records, utility bills, employment or pension documents and bank statements; and
• every message sent to the French tax service about the account or the filing.

This separation prevents a common error: telling the tax office that you are non-resident merely because you still pay UK tax, or telling it that you are resident merely because you own a house in France. Both statements may be incomplete. The number is an administrative gateway; residence and treaty relief are legal conclusions supported by facts.

B. What documents and first-return route should I use if I cannot create the account?

Start by identifying which of three situations applies.

First, you already have a French tax number and recent French tax documents. The official impots.gouv.fr guidance for non-residents creating an espace Finances publiques says that the number has 13 digits. For an existing income-tax record, the online-access number and the revenu fiscal de référence, meaning the reference taxable income shown on the tax notice, can also be requested. The number is normally printed on an income-tax notice or a local-tax document. Use the latest document, not a number copied from an old letter where a household or address has changed.

Secondly, you have no usable online credentials but the French administration has already issued a number. The same official page provides a route for a person who has a tax number but is not liable for French income tax, including a person liable for taxe d’habitation on a second home or taxe foncière. The form asks for civil status, a foreign postal address and a copy of an identity document. After the identity check, the administration sends an email allowing the account to be created with the tax number and date of birth. You then choose an email address and password and must click the validation link within eight hours. Save the submitted form, the acknowledgement and the validation email.

Thirdly, this is your first French declaration of income or assets. The official instruction is important: if you wish to declare income or patrimoine, meaning assets or wealth, in France for the first time, the declaration cannot be completed online. The non-resident page directs you to send a paper return to the relevant tax service. A blocked account is not a legal reason to wait until the online system becomes available. Send the paper return by a trackable method, keep a complete copy and retain the postal proof of delivery. If you are moving to France and need to understand the first return, the firm’s related guide on the first French tax return, split-year residence and UK bank accounts addresses the wider transition; this article focuses on the access and dispute problem.

The paper route does not mean that every British person must file every French form. It means that the first filing must be allocated correctly. The relevant return can depend on French-source income, rental activity, capital gains, property status and the person’s tax residence. A first return may require supporting schedules, a declaration of foreign accounts or evidence explaining the UK position. Do not send a blank or contradictory form simply to obtain a number. Explain the reason for the first filing in a covering letter and state whether you are asking the administration to open an account, issue a number, process a return or correct a residence classification.

The legal basis for the income declaration is Article 170 of the French General Tax Code. The current provision says that “toute personne imposable audit impôt est tenue de souscrire et de faire parvenir” a detailed income declaration, with the contents depending on the situation. The duty is driven by liability and the relevant tax rules, not by whether the taxpayer can log in. Conversely, the existence of a number does not prove that all of the person’s worldwide income is taxable in France.

If you are French tax-resident, check the separate obligation for UK bank accounts and other accounts held abroad. Article 1649 A of the French General Tax Code requires individuals domiciled or established in France to declare qualifying foreign accounts alongside the income return. The article states that the references to accounts “ouverts, détenus, utilisés ou clos à l’étranger” must be declared in the prescribed circumstances. A UK current account, savings account or investment account may need separate analysis; the fact that it was opened before Brexit does not settle the question. An ISA, pension arrangement or QROPS can raise additional classification questions and should not be forced into a standard bank-account box without checking its nature.

Prepare one evidence pack before contacting the administration:

• a clear copy of the British passport or other accepted identity document;
• proof of the current UK and French addresses, with dates;
• all French tax notices, property references and correspondence;
• the date you acquired or occupied the French property and whether it was rented, vacant or used as a second home;
• UK tax references and documents showing the tax years concerned;
• a calendar of days spent in France and the UK if residence may be disputed;
• details of any French income, withholding, pension or property income; and
• a chronology of each attempt to create, access or unblock the online account.

In the contact form, select the problem that matches the request: creation of a private account, access to online services, income tax, local taxes or a formal claim. A French tax office can ask you to deal with the Service des impôts des particuliers non-résidents, abbreviated SIPNR and meaning the Non-Residents’ Tax Service, or with a local service for property-related matters. The official impots.gouv.fr contact and appointment page asks the user to identify whether they live outside France and what the request concerns. Quote the tax number if known, the property address, the tax year and the exact notice. This is much more effective than sending a general message saying that the account “does not work”.

II. What should I do if the account is blocked or a late return brings a tax penalty?

A. How do I unblock the account, preserve proof and challenge the assessment?

Treat the account problem as an urgent operational issue and the tax assessment as a separate legal issue. A technical block does not automatically cancel a filing deadline, a payment date or a right to make a claim. At the same time, the administration should be told immediately that access prevented an online action and should receive the evidence of the attempted action.

The official impots.gouv.fr blocked-account guidance asks the taxpayer to check FranceConnect history, look for an unexpected connection email and change the passwords of the relevant identity providers and email account. FranceConnect is the French single-sign-on service used by several public services. If the security checks do not reveal a compromise, request removal of the block from the centre des Finances publiques shown on the latest document or found through the contact page. The guidance states that identity must be proved with an original identity document at the counter, not a photocopy.

The official Service-Public procedure for accessing the tax account adds a practical timetable: after failed authentication, a six-digit unblocking code is sent by post in approximately one week; if it has not arrived within ten days, the user is directed to attend the tax office with identification. A British resident abroad should contact the service before travelling and ask whether an appointment, a consular solution or another identity route is available. Do not assume that a UK address removes the identity requirement. Keep screenshots of the error, the date and time of each attempt, the browser or FranceConnect route used, the automatic emails, the postal envelope and every reply.

If a first return or a correction is due, send the paper filing or a written explanation at the same time as the request to unblock the account. On the first page, state that the online route was unavailable, identify the tax year and attach the delivery evidence. If you later obtain access, upload the same material through secure messaging without deleting the paper proof. The account route is then documented twice, while the substantive filing remains traceable.

If the notice is wrong, use a formal réclamation contentieuse, meaning a formal tax claim seeking cancellation or reduction of an assessment, rather than relying only on a service message. Article L190 of the French Tax Procedures Code places claims about errors in the tax base or calculation, and claims based on a statutory or regulatory right, within the contentious tax procedure. This is the route for arguing, for example, that France treated a UK-resident owner as French-resident without applying the treaty, that income was allocated to the wrong year, that a tax was duplicated or that a penalty was calculated on an incorrect principal amount.

The first claim normally goes to the territorial tax service. Article R*190-1 of the French Tax Procedures Code states that a taxpayer who wishes to challenge all or part of a tax must first send a claim to the appropriate territorial service. Use the service shown on the notice or the service identified by the official contact questionnaire. Keep proof that the claim was sent and received. A secure message may be useful, but for a time-sensitive formal claim use a channel that proves the content and date.

The claim must be complete enough to be understood without a later conversation. Under Article R*197-3 of the French Tax Procedures Code, “Toute réclamation doit à peine d’irrecevabilité” identify the tax challenged, explain the grounds and conclusions, bear the author’s signature and include the notice or evidence of payment. In practical English, the document should state:

• your full name, tax number, address and contact details;
• the exact tax, notice number, year and amount challenged;
• the relief requested, such as cancellation of the residence adjustment, reduction of tax, withdrawal of a surcharge or repayment;
• the facts in date order, including the failed account attempts;
• the legal grounds, including Article 4 B, the treaty or the relevant filing rule;
• the evidence proving the UK position, the French property facts and the filing history; and
• a signed copy of the notice or the payment evidence required for the particular tax.

A request for a remise gracieuse, meaning a discretionary request for relief from a penalty or payment difficulty, can be added when the facts show good faith, hardship or an administrative access problem. It is not the same as a legal claim that the assessment is wrong. Make both requests distinct: the contentious claim protects the legal argument and the discretionary request explains why relief should be granted. If the principal tax is correct but a penalty is excessive, say so. If the principal tax is itself wrong, challenge the principal first and address the penalty consequentially.

The account block may support the narrative, but it is rarely enough by itself. Explain why the filing was late, when you first tried to comply, what the administration told you, when the return was sent and whether you corrected the position voluntarily. A British owner who simply waited for an online account can face a different assessment from a taxpayer who repeatedly requested a number, sent a paper return and kept proof. The file should make that difference visible.

B. Which deadlines, penalties and France–UK treaty points control the appeal?

The amount on a French notice may contain several components. Separate the principal tax, a declaration surcharge, late-payment interest and a payment surcharge. Their legal tests and possible arguments are not identical.

For a late or missing declaration, the current Article 1728 of the French General Tax Code provides a 10% increase where a declaration is late and there has been no formal notice, or where it is filed within thirty days after a formal notice. A mise en demeure, meaning a formal demand to file within a stated period, can lead to a 40% increase if the return is not filed within the following thirty days. The text also contains an 80% category for concealed activity. Those rates do not mean that every first return by a British person automatically receives a 10% surcharge. The administration must identify the filing obligation, the due date, the notice and the facts supporting the rate.

Article 1758 A is a different provision. The current Article 1758 A of the French General Tax Code concerns late or inaccurate income declarations that reduce tax or increase a credit. It sets a 10% increase and raises it to 20% when the late filing occurs within thirty days of a formal notice, subject to its own exclusions and interaction with Article 1728. If the tax office has applied both provisions, ask it to identify the legal basis and explain why the combination is permitted.

Late-payment interest is not the same as a declaration surcharge. Under Article 1727 of the French General Tax Code, “Le taux de l’intérêt de retard est de 0,20 % par mois.” The article also sets the calculation start and end points and specific rules for income tax, an assessment following a late declaration and spontaneous regularisation. Check the dates used in the calculation rather than accepting a total copied into the notice. A taxpayer who files promptly, pays the principal or agrees a payment arrangement may have arguments about the calculation, but the result depends on the exact tax and procedural history.

Payment after the deadline can create another increase. Article 1730 of the French General Tax Code provides for a 10% increase for late payment of specified liabilities, including income tax, second-home taxe d’habitation, property taxes and wealth tax, with the provision describing the relevant notice and forty-five-day period. This is distinct from the filing penalties in Articles 1728 and 1758 A. A challenge should show which part of the notice is being disputed and whether payment was attempted or prevented by the account problem.

Do not put all of your legal argument into a general phrase such as “Brexit caused the error”. Brexit may explain why a British person no longer has the same EU administrative route, but it does not itself decide French tax residence or erase a French filing duty. Address the relevant facts:

• Where was your permanent home available during the tax year?
• Where did your partner and dependent children normally live?
• How many days did you spend in each country, and for what purpose?
• Where did you work, receive a pension or conduct a business?
• Which country held the centre of your personal and economic relations?
• Was the French property a furnished second home, a rented property, an occupied home or an asset held for another purpose?
• What did HMRC treat as your residence, and what evidence supports that conclusion?
• Did France tax only French-source income, or did the administration treat you as taxable on worldwide income?

The treaty tie-breaker is not a device for choosing the country with the lower bill. It coordinates residence when domestic rules overlap. The official treaty text uses the concept of a “permanent home available to him” and then compares closer personal and economic relations. If you rely on the treaty, attach evidence directed to each step. A UK tax return alone may show a UK filing, but a residence certificate, HMRC correspondence, the UK home’s use, family records and work evidence can make the argument more persuasive. French accommodation, substantial work, family life or productive assets can support the contrary conclusion.

The deadline for the formal claim must be checked against the tax type and the wording of the notice. Article R*196-1 of the French Tax Procedures Code states, for the ordinary categories described there, that claims “doivent être présentées à l’administration au plus tard le 31 décembre de la deuxième année suivant celle” of the relevant assessment, payment or event. The same article gives different rules for some local taxes, withholding and situations where the taxpayer learns with certainty that a direct tax was wrongly assessed or duplicated. Use the current notice and the current version of the provision when calculating the final date; never assume that one deadline applies to income tax, taxe foncière and a withholding claim.

The timing rule has a procedural safeguard. In Conseil d’État, 27 June 2005, no. 259368, published in the Lebon Reports, the court held that the absence of required information about the claim and its deadline could “faire obstacle à ce que les délais prévus par les articles R. 196-1 et R. 196-3 du livre des procédures fiscales soient opposables au contribuable”. This does not excuse delay in every British-owner case. It means that the notice, its appeal instructions and the way it was served should be checked. Keep the envelope, the electronic availability date, the account messages and any translation or forwarding evidence.

If the notice arrived while you had no number or no online account, make that chronology central but not exclusive. The better request is usually:

1. issue or confirm the French tax number and restore secure access;
2. accept and process the first paper declaration or late correction;
3. correct the residence or source-income classification if the evidence requires it;
4. withdraw or reduce any declaration and payment surcharges under the applicable rules;
5. recalculate late-payment interest from the legally correct dates; and
6. confirm the remaining amount, payment deadline or agreed arrangement in writing.

For a non-resident, a French property tax dispute may also involve the property’s address, ownership share, occupancy, exemption, payment mandate or the distinction between local-tax administration and the SIPNR. The owner’s online income-tax account is not always the only service involved. That is another reason to quote the notice number and tax type rather than sending the same message to every address.

Finally, consider what can be proved today. A useful appeal pack is not a collection of undated screenshots. It has a timeline, numbered exhibits and a short explanation of the legal consequence of each exhibit. Exhibit 1 can be the notice, Exhibit 2 the failed login, Exhibit 3 the request for a number, Exhibit 4 the identity documents, Exhibit 5 the paper return and delivery proof, and later exhibits the residence and treaty evidence. Translate only what is necessary, but provide the original documents and explain the translation. Ask for a written decision. If the administration rejects the claim or does not provide the requested correction, the next procedural step should be assessed from the rejection, the tax type and the competent court.

Conclusion

For a British person in France, the fastest safe route is not to argue about Brexit in the login screen. First establish whether a French tax number already exists. If it does, use the official non-resident route or request an unblock with the identity evidence required. If this is the first declaration of French income or assets, send the paper return and keep delivery proof; the official guidance expressly directs first-time declarants away from the online route. Then separate access, filing, residence, penalty and payment issues in the written record.

A French tax number is an administrative identifier, not a treaty verdict. Owning a French property can create a local-tax record without making you French-resident, while a move, family life, work or economic interests can create French residence despite continuing UK ties. If a notice contains a surcharge, calculate the deadline under the relevant tax rule, make a formal claim with the required notice and signature, and support the France–UK position with dated evidence. The central questions are what you had to declare, when the administration received it, what blocked compliance and which legal rule applies to each amount.

Official sources checked for this guide include the non-resident account guidance, the blocked-account guidance, Service-Public, the cited provisions of the French General Tax Code and French Tax Procedures Code, the cited decisions on Légifrance and the UK government treaty text.

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