You moved back to Britain, but you kept the flat in France, and it is now let to a tenant. Every month the rent lands in your account, and every year two tax offices take an interest in it: France, because the flat stands on French soil, and the United Kingdom, because you live in Britain again and pay tax there on your worldwide income. After Brexit, this everyday situation worries many returning owners. Will the rent be taxed twice? Does leaving France mean lighter French paperwork, or heavier bills? Can you still choose the simple flat-rate cost allowance, or should you deduct your real expenses? And what happens if the French bill looks wrong — where do you complain from London, Manchester or Edinburgh, and what proof do you need?

This guide answers those questions in order. It is written for a British reader who is now resident in the United Kingdom for tax purposes and receives rent from letting a residential flat in France, usually unfurnished. A revenu foncier, meaning rental income from an unfurnished letting, follows different rules from a furnished letting, which France treats as a small business profit. Each French term is explained the first time it appears. The first part explains how France taxes that rent when the owner lives in Britain: which tax category applies, how the taxable profit is worked out, and which rates and social levies apply to a non-resident. The second part explains how the United Kingdom relieves the double burden through its Foreign Tax Credit Relief, and how you challenge an excessive bill on either side of the Channel, with the exact paperwork that wins refunds. All rates and thresholds are those in force for the 2026 filing season, checked against the official texts during this run.

I. How France taxes your French rent when you live back in Britain

A. Which French tax box your rent falls into and how the profit is worked out

France taxes the rent at source, because the property is in France, even though you now live in Britain. Article 164 B of the French General Tax Code (Code général des impôts, the main French tax statute) provides that “Les revenus d’immeubles sis en France ou de droits relatifs à ces immeubles” are treated as French-source income: article 164 B. In plain English, rent from a building standing in France is taxable in France first, regardless of where the owner lives. Whether you are still French tax resident is decided separately under article 4 B, which treats as French resident persons “qui ont en France leur foyer ou le lieu de leur séjour principal”, meaning those whose household home or principal place of abode is in France: article 4 B. Once your household home has genuinely moved back to Britain, France taxes you as a non-résident, a non-resident, but it keeps the right to tax the French rent.

The next question is the category. An unfurnished residential letting falls into revenus fonciers, rental income from bare property. Article 14 states that “sont compris dans la catégorie des revenus fonciers” the income from built property such as houses and factories, when it is not part of a commercial business: article 14. A furnished letting is different: it is taxed as bénéfices industriels et commerciaux (BIC), industrial and commercial profits, the business-profits category. The official impots.gouv.fr guidance for non-residents confirms the split: rent from bare premises is taxed on the progressive scale under revenus fonciers, while furnished rent is taxed under BIC, with social levies at 17.2% on the former and, for income received from 2025, 18.6% on the latter: impots.gouv.fr, non-resident rental income. The distinction matters because each category has its own return forms, its own flat-rate allowance and its own deficit rules, so identifying the right box is the first control before any figure goes on a return.

Within revenus fonciers, two methods compete. The starting point is gross receipts. Article 29 defines the base bluntly: “le revenu brut des immeubles ou parties d’immeubles donnés en location, est constitué par le montant des recettes brutes perçues par le propriétaire”, meaning gross income is what the owner actually receives, plus any expenses normally borne by the owner but passed to the tenant by the lease: article 29. From that gross figure, the régime réel, the actual-expenses method, deducts the real costs listed in article 31. That article opens with the principle that “Les charges de la propriété déductibles pour la détermination du revenu net comprennent” repair and maintenance spending, insurance premiums, co-ownership provisions, improvement works on dwellings, management fees, loan interest on the purchase and the taxe foncière, the French annual property ownership tax: article 31. The competing method is the micro-foncier, a simplified flat-rate scheme available when annual gross rent outside certain structures “n’excède pas 15 000 €”, in which case “le revenu imposable correspondant est fixé à une somme égale au montant de ce revenu brut diminué d’un abattement de 30 %”: article 32. In plain terms, below 15,000 euros of yearly gross rent you may simply declare the gross amount and France grants a 30% cost allowance, with no questions asked and no receipts to keep for the allowance itself.

A worked example shows why the choice matters. Take a Lyon one-bedroom flat let bare for 900 euros a month, or 10,800 euros a year, owned outright by a former expatriate now living in Leeds. Under micro-foncier, the taxable amount is 10,800 minus 30%, which is 7,560 euros. Under the régime réel, suppose the owner paid 1,100 euros of taxe foncière, 950 euros of managing-agent fees, 600 euros of insurance, 1,400 euros of deductible co-ownership charges and 2,800 euros of loan interest, a total of 6,850 euros. Taxable profit would then be 10,800 minus 6,850, which is 3,950 euros — barely half the micro-foncier figure. Reverse the facts, with a debt-free flat, a reliable tenant and almost no charges, and micro-foncier wins. The practical rule is therefore to compute both every year: micro-foncier favours low-cost flats, while the real method favours mortgaged flats, recently refurbished flats and flats with heavy charges de copropriété, the service charges of a French co-owned block. One caution from the official guidance: owners must also declare each year, before 1 July, through the Gérer Mes Biens Immobiliers online property register, on what basis each property is occupied and who the occupier is where it is let: impots.gouv.fr, non-resident rental income. That declaration does not compute the tax, but missing it draws penalties that inflate an otherwise modest bill.

Furnished lettings deserve a short aside, because many returning owners furnish the flat to widen the tenant pool. Furnished rent is business profit, and the simplified micro-BIC scheme has its own turnover ceilings, including “1° bis 15 000 € s’il s’agit d’entreprises dont l’activité principale est de louer directement ou indirectement des meublés de tourisme”, meaning 15,000 euros for businesses mainly letting tourist-furnished accommodation: article 50-0. The allowance percentages and accounting duties differ from revenus fonciers, and recent case law confirms the categories must not be confused. On 13 March 2026 the Conseil d’État, France’s supreme administrative court, held that “Constituent des revenus d’immeubles au sens de ces dispositions les loyers issus d’immeubles situés en France, quelle que soit la catégorie d’imposition dont ils relèvent”, meaning rents from French buildings count as building income whatever tax category they fall into: Conseil d’État, 13 March 2026, no. 503496. The tenants in that case, Swiss residents letting a furnished villa seasonally, had argued that business-category rents escaped the solidarity levy on property income; the court disagreed and upheld the charge. For a British owner the lesson is symmetrical: choosing furnished or bare changes the income-tax computation, but it does not move the rent outside France’s taxing grasp.

B. The non-resident rates, the average-rate safety valve and the social levies that surprise British owners

Once the taxable profit is fixed, the rate is where non-resident status bites. France applies the same progressive scale to residents and non-residents, but it guarantees itself a minimum take from the latter. Article 197 A provides that “l’impôt ne peut, en ce cas, être inférieur à un montant calculé en appliquant un taux de 20 % à la fraction du revenu net imposable inférieure ou égale à la limite supérieure de la deuxième tranche du barème de l’impôt sur le revenu et un taux de 30 % à la fraction supérieure à cette limite”, meaning the tax on French-source income cannot fall below 20% on the slice up to the top of the second (11%) band and 30% above it: article 197 A. For income year 2025, declared in 2026, the 11% band tops out at 28,797 euros per share, so a non-resident with 7,560 euros of taxable rental profit pays at least 20% on it, about 1,512 euros before the UK credit, even if the ordinary scale would have charged less. Above the threshold the 30% floor applies. This floor has been heavily litigated, including a constitutional challenge transmitted to the Conseil d’État on 3 February 2023 concerning non-residents whose entire income is French-source: Conseil d’État, 3 February 2023, no. 468904. Owners should therefore treat the minimum as the default outcome and the lower scale charge as something to be claimed, not assumed.

The claim route is the taux moyen, the average-rate option. The same article 197 A adds that “lorsque le contribuable justifie que le taux de l’impôt français sur l’ensemble de ses revenus de source française ou étrangère serait inférieur à ces minima, ce taux est applicable à ses revenus de source française”, meaning that where the owner proves the French tax rate on all worldwide income would sit below the floors, that lower average rate applies to the French income: article 197 A. In practice the owner declares worldwide wages, pensions and rents to the French office for non-residents (Service des impôts des particuliers non-résidents, the tax office handling taxpayers living abroad), computes the average rate that worldwide picture would produce, and France applies that rate to the French rental profit if it is lower than 20%. A retired owner in York with a small UK pension and one modest French rent will often win a rate well under 20%; a City earner with a large London salary will not, and the 20%/30% floor will stick. The proof is documentary: the UK P60 or self-assessment computation, pension statements and evidence of family shares (quotient familial, the French system dividing income into shares by household composition). Because the French office cannot check HM Revenue and Customs records directly, a thin file is refused and the floor applied, so the average-rate claim lives or dies on the exhibits attached.

Income tax is only half the French bill. Social levies come on top, and they are the line that most shocks British owners, because the United Kingdom has no equivalent surcharge on rental profit. The base rule sits in article L. 136-6 of the Social Security Code (Code de la sécurité sociale), which charges a contribution on property income “assise sur le montant net retenu pour l’établissement de l’impôt sur le revenu”, meaning assessed on the net amount used for income tax: article L. 136-6. For bare lettings the headline social-levy rate is 17.2%, as the official non-resident page confirms. Since 1 January 2019, however, persons covered by a compulsory social-security scheme of a European Economic Area state or Switzerland escape the CSG (Contribution sociale généralisée, the general social contribution) and CRDS (Contribution au remboursement de la dette sociale, the social-debt repayment contribution) components. The decisive point for this article’s readers is stated on the official page itself, which confirms that British residents keep the CSG-CRDS exemption despite the United Kingdom having left the European Union: impots.gouv.fr, non-resident rental income. What remains is the prélèvement de solidarité, the solidarity levy, and article 235 ter is explicit: “Le taux des prélèvements de solidarité mentionnés au I est fixé à 7,5 %”, the rate is 7.5%: article 235 ter. The 2026 Conseil d’État decision quoted above then closes the loop for doubters: “sont assujetties au prélèvement de solidarité prévu au 1° de l’article 235 ter du code général des impôts les personnes physiques non-résidentes, à raison des loyers qu’elles perçoivent, issus de la location d’immeubles situés en France”, meaning non-resident individuals are liable to the levy on rents from letting French buildings: Conseil d’État, 13 March 2026, no. 503496.

To claim the CSG-CRDS exemption in practice, the return must carry the signal. The official page instructs owners to report total property or business income, tick boxes 8SH (first declarant) and/or 8SI (second declarant) in section 8 of return 2042-C, and, for a bare letting where only one spouse of a married or civil-partnership couple qualifies, to state the exempt property income in box 8RF: impots.gouv.fr, non-resident rental income. Instalments (acomptes, advance payments) due from the September after the return are then computed without the social charges, with the 7.5% collected on the balancing bill. Two cash-flow points complete the picture. First, no tax is withheld from the rent itself: unlike wages, bare rents are paid gross by the tenant, and the owner is billed after assessment, so a reserve for the French bill should sit untouched all year. Second, where no property income remains in a later year, box 4BN of return 2042 should be ticked so the instalment machinery stops: the same official page gives that instruction expressly. Owners who sell the flat later face a different computation, capital gains on the sale, which is covered in our companion guide for British owners disposing of a former French home: leaving France and selling the former home. Keeping the letting and the later sale analytically separate avoids mixing the annual rental rates with the sale-time rules.

II. How the United Kingdom relieves the double bill and how you challenge an excessive charge

A. Declaring the French rent in Britain and claiming Foreign Tax Credit Relief

Residence in Britain brings the rent into the United Kingdom net. A person resident in the United Kingdom is taxable there on worldwide income, including rent from a flat abroad, which must be reported to HM Revenue and Customs on the foreign pages (SA106) of the self-assessment return, with allowable expenses deducted under United Kingdom rules. The France–United Kingdom double tax treaty of 19 June 2008, published in the official French tax commentary, allocates the primary right to tax rental income to the state where the property stands and obliges the owner’s state of residence to relieve the resulting double taxation: BOFiP, France–United Kingdom treaty. The United Kingdom gives that relief as Foreign Tax Credit Relief, explained in the official helpsheet for relief on foreign tax paid: GOV.UK, relief for foreign tax paid (HS263). The mechanism is a credit, not a deduction: each pound of French income tax on the same rent reduces the United Kingdom tax on that rent by a pound, but only down to zero — the credit cannot exceed the United Kingdom tax computed on the same income, and any French tax above that ceiling is simply unrelieved.

The ceiling is where owners lose money through inattention, so it deserves a worked example. Suppose the Leeds owner from Part I has 7,560 euros of French taxable profit and pays 1,512 euros of French income tax plus 567 euros of solidarity levy at 7.5%. Converted at a steady rate, say 8,600 pounds of gross rent with 4,600 pounds of expenses allowable under United Kingdom rules, the United Kingdom profit is 4,000 pounds. If the owner’s marginal United Kingdom rate on that slice is 20%, the United Kingdom tax on the rent is 800 pounds. The credit for French income tax is then capped at 800 pounds: the remaining French income tax is not refunded by London, and the French social levy, which is not an income tax covered in the same way, generally does not enter the credit computation at all. Three consequences follow. First, the French computation directly controls the unrelieved cost: every euro shaved off the French taxable profit by the régime réel or by the average rate reduces dead tax that London will never give back. Second, expense timing differs between the two systems — French loan interest and co-ownership provisions are not always mirrored in the United Kingdom computation — so both returns should be prepared from one reconciled schedule rather than in isolation. Third, the French assessment (avis d’imposition, the official tax bill) is the proof HM Revenue and Customs expects: file the United Kingdom return with the French figures estimated where the French bill has not yet arrived, then amend once the avis lands, keeping the amendment within the United Kingdom time limits. Owners who report the gross rent in one country and the net in the other, or who claim the credit before the French assessment exists, invite enquiries on both sides.

B. Proof, deadlines and challenges: the paperwork that wins refunds

Whether the dispute is French or British, the file decides the outcome, and the file is built during the year, not after the bill arrives. On the French side the backbone is the annual return: article 170 requires that “toute personne imposable audit impôt est tenue de souscrire et de faire parvenir à l’administration une déclaration détaillée de ses revenus et bénéfices”, meaning every person liable must send the administration a detailed return of income and profits: article 170. For a bare letting that means return 2044 (or the 2044-SPE special form) detailing each property’s receipts and charges, carried to return 2042, plus 2042-C boxes 8SH/8SI and 8RF for the CSG-CRDS exemption described above. Around that core, the winning file holds the lease and its renewals, the rent ledger or bank statements showing receipt, the managing agent’s annual statement (relevé de gérance), invoices for every deducted repair, insurance certificates, loan-interest statements, taxe foncière bills, co-ownership charge calls and general-meeting minutes approving works, and, for an average-rate claim, the household’s worldwide income proof with a short reconciliation between the sterling documents and the euro figures declared. Keep translations short and factual where an exhibit is challenged; a one-page certified-equivalent summary beats a bundle of unexplained statements.

Deadlines structure both systems. In France the online return for non-residents generally falls in May or June, the Gérer Mes Biens Immobiliers occupancy declaration runs to 1 July each year, and any complaint (réclamation, the formal challenge to an assessment) goes through the secure messaging of the impots.gouv.fr personal account or by letter to the non-residents’ tax office, with the assessment reference, the precise ground — wrong category, forgotten charges, missed average rate, wrongly charged CSG-CRDS — and the exhibits attached. If the administration maintains the bill, the dispute moves to the administrative court (tribunal administratif), where the two Conseil d’État decisions cited in this guide show how judges read the texts: categories do not defeat the solidarity levy, and the 20%/30% floor is applied as written unless the average rate is proved. In the United Kingdom, the self-assessment return is due by 31 January online following the tax year, the SA106 foreign pages carry the French rent and the credit claim, and errors are corrected by amending the return within twelve months of the filing deadline, with overpayment relief running four years from the end of the tax year as a longer stop. Interest runs on late-paid tax in both countries, and France applies surcharges for undeclared property income, so a challenge should always be paired with payment of the undisputed part: contesting the whole bill while paying nothing converts a rate argument into a penalty file. The recurring pattern in successful cases is unglamorous — right category, both computations compared yearly, exemption boxes ticked, worldwide proof attached, French assessment kept for London — and it beats every shortcut.

Conclusion

A British owner back home who lets a French flat answers to two treasuries in a fixed order: France taxes the rent first because the building is French, and the United Kingdom taxes it second with a credit capped at its own charge. Within France, the owner’s three decisions set the bill — bare or furnished category, flat-rate 30% allowance or real expenses, minimum 20%/30% rate or proved average rate — and the social-levy position for British residents is now settled in the owner’s favour at 7.5% solidarity with CSG-CRDS exempted, provided the return carries the right boxes. Within Britain, the credit relieves the French income tax but never more than the United Kingdom tax on the same rent, which makes the French computation the decisive battleground. Build one reconciled file during the year, declare in both countries from it, tick the exemption boxes, attach worldwide proof for any average-rate claim, and challenge a wrong bill with the assessment reference and exhibits rather than with silence. Done that way, the cross-Channel rent stays what it should be: a second income, not a second dispute.