If the general withdrawal agreement is not ratified, three scenarios, which may overlap, are possible.
French residents receiving UK-source income: taxpayers are liable, on their income from assets and revenue from investments, to the unlimited levying of tax and social security contributions in France subject to the provisions of the France/UK Double Taxation Convention of 19 June 2008 which provide, inter alia, that the relevant taxpayers are entitled to a tax credit in the same amount as the British tax for capital gains on property or a tax credit in the same amount as the French tax for property income. As social levies are covered by the Convention, the tax paid in the UK may be offset against the social levies where applicable.
British residents receiving French-source property income: as a matter of principle, property income (rent and capital gains on property) is subject to social levies under domestic law. Pursuant to the France/UK Double Taxation Convention of 19 June 2008, the UK should consider that French social levies provide entitlement to a tax credit which will be offset against the British tax assessed on this income.
Irrespective of the place of residence, persons who are not affiliated to a compulsory French social security scheme but who are governed by social security legislation subject to the provisions of Regulation (EC) No 883/2004 on the coordination of social security systems are concerned by a provision laid down in the Social Security Budget Bill (PLFSS) for 2019 which exempts them from the General Social Security Contribution (CSG) and the Social Security Debt Repayment Contribution (CRDS) assessed on income from assets and revenue from investments. Exemption from these two contributions applies on the basis of legislative conditions to all non-affiliated persons in France who are affiliated to a compulsory social security scheme in the UK. If the general withdrawal agreement is not ratified, these persons will no longer be entitled to the exemption as British social security legislation will no longer be subject to the provisions of the above-mentioned EU Regulation.
Lastly, the solidarity levy assessed on income from assets and revenue from investments will be maintained after the UK leaves the EU for all taxpayers, regardless of whether the latter are affiliated to a compulsory social security scheme in the UK or not.