A cross-border worker who lives in France and works in Switzerland chooses their health insurance once: the Swiss LAMal, or the French scheme, often called the "CMU frontalier". The choice is made within three months of starting work in Switzerland, it cannot be undone, and without an explicit choice the LAMal applies (CLEISS, "Droit d'option des frontaliers France-Suisse").
The two options are usually compared on health: the LAMal premium on one side, the French contribution on the other, and what each one reimburses. This article leaves that comparison aside. It looks at the other half of the choice, the one people often discover years later when they sell securities: what each scheme takes from your investments.
The rule: 7.5% instead of 18.6%
A French tax resident insured under the compulsory social security of Switzerland, or of another EEA state, who is not covered by a compulsory French scheme, owes no CSG or CRDS on income from assets and investments. Only the 7.5% solidarity levy remains due (service-public.gouv.fr, page F2329, checked 30 June 2026; CSS art. L136-6 I ter and L136-7, from the LFSS 2019; CGI art. 235 ter).
Why 7.5% and not zero: since 2019 the solidarity levy funds the State budget rather than social security. It therefore escapes the European rule that a person contributes to one scheme only, the rule the Court of Justice of the EU applied in the de Ruyter ruling of 26 February 2015. The 18.6% of social charges on gains and dividends in 2026 break down into 10.6% of CSG, 0.5% of CRDS and the 7.5% solidarity levy; the 17.2% on rents, life insurance and home-savings plans into 9.2%, 0.5% and the same 7.5%.
A cross-border worker who chose the French scheme is "covered by a compulsory French scheme": they owe the full social charges, like an employee in France. Income tax does not change from one scheme to the other: 12.8% under the flat tax, or the progressive scale if the overall election is made.
What it changes, income by income
| income (2026) | French scheme | insured under the LAMal |
|---|---|---|
| gain or dividend on a brokerage account (flat tax) | 31.4% | 20.3% |
| gain on crypto | 31.4% | 20.3% |
| PEA over five years old (gain) | 18.6% | 7.5% |
| PEA under five years old (gain) | 31.4% | 20.3% |
| life insurance under eight years old (gain) | 30% | 20.3% |
| life insurance over eight years old (gain) | 17.2% of social charges, plus 7.5% income tax above the €4,600 allowance (€9,200 for a couple) | the 7.5% solidarity levy, plus the same income tax above the allowance |
| PEL or CEL opened since 2018 (interest) | 30% | 20.3% |
| CEL opened before 2018 (interest) | 17.2% | 7.5% |
| rents (property income) | income-tax scale + 17.2% | income-tax scale + 7.5% |
| gain on property | 19% + 17.2%, after the holding-period allowances | 19% + 7.5% |
The PEA is France's equity savings plan; the PEL and the CEL are its regulated home-savings plans.
Income tax and social charges in 2026, rents counted in the 30% bracket. The gap is €1,110 on a brokerage-account or PEA gain, €970 on life insurance under eight years old or on rents: that is the CSG and the CRDS, 11.1 points on gains and dividends, 9.7 points on the rest. IgniFI's calculation from service-public.gouv.fr, page F2329.
An example, to set the orders of magnitude. A €30,000 gain on a brokerage account, realised in 2026, bears 31.4% in the French scheme, that is €9,420. Insured under the LAMal, the same gain bears 20.3%, that is €6,090: €3,330 less, the CSG and the CRDS. On a PEA over five years old, a €30,000 gain costs €5,580 in the French scheme and €2,250 under the LAMal.
The capital of the Swiss pillars
The droit d'option also reaches what comes out of the 2nd pillar. Paid in one go to a French resident who worked in the private sector, that capital is taxed in France (a Swiss public employee's stays taxed in Switzerland): on election, a 7.5% levy after a 10% allowance, that is 6.75% of the gross capital (CGI art. 163 bis II and 158-5 b quinquies). It is a replacement income: the CSG, CRDS and Casa on pensions, 9.1% at the standard rate in 2026 (service-public.gouv.fr, page F2971), are owed only by someone covered by the French health insurance. In all: 6.75% under the LAMal, 15.85% in the French scheme.
On a capital of CHF 300,000, the gap is CHF 27,300: CHF 20,250 under the LAMal, CHF 47,550 in the French scheme. The tax the Swiss fund withholds at source is refunded on request, with a certificate from the French tax office, within three years of the payment.
A 3a paid from a salary taxed at source follows the same rule as the 2nd pillar. The 3a of a cross-border worker taxed in France, whose payments were never deductible, is taxed on its gains alone, at the flat tax: 20.3% or 31.4%, depending on the same choice of health insurance.
The French scheme's contribution
The French scheme has a cost the LAMal does not have in this form: a contribution of 8% of income above an allowance of €12,015 in 2026, a quarter of the annual social security ceiling (CSS art. L380-3-1; order of 22 December 2025, ceiling of €48,060). It is assessed on the income of two years before declared to the Urssaf, and that income is not only the Swiss salary: investment income, property income and gains on securities and property are part of it.
For savings, the consequence is rarely written down: as long as the household's income is above the allowance, each euro of gain realised in the French scheme adds 8 cents to the contribution two years later. The €30,000 gain of the example, taxed €9,420 in the year of the sale, then adds €2,400 to the contribution.
When the affiliation changes
The affiliation follows the moment of the income. It lasts as long as the cross-border worker works in Switzerland or, once retired, as long as they receive only a Swiss pension and stay with the LAMal. A cross-border worker who stops working in Switzerland before a Swiss pension is paid comes under the French health insurance: the full social charges apply again to what they sell from then on.
For anyone aiming at financial independence before retirement age, this is the point to keep in mind: gains realised in the years with neither a Swiss salary nor a Swiss pension are those of someone in the French scheme.
The tax return
The LAMal affiliation is reported in the tax return; our article on box 8SH explains where, and how to claim back past years. Income on which a French bank or insurer withholds at source may be withheld at the full rate: the excess is then claimed from the tax office, with proof of affiliation.
What IgniFI does
In Settings › Region & currency, or in the opening questionnaire, a French resident answers "Yes, cross-border", then gives their canton of work and their health insurance. From then on, every calculation that carries a social charge takes theirs: the withdrawal plan's pockets, the net dividends on the dashboard, the copy-trading simulator, the tax on a PEL's or a CEL's interest. A 2nd-pillar capital is planned at 6.75% or at 15.85%. Until the question is answered, the app uses the French charges: the rate that cannot flatter a figure.
Two things are not computed, and the app says so: the French scheme's 8% contribution, which falls on the whole household's income two years later, and a change of affiliation during retirement, since the plan applies today's declared cover to the whole of retirement. The page Personal finance for France–Switzerland cross-border workers goes through each rule, with what the app does about it.
Frequently asked questions
Does a cross-border worker under the LAMal still pay social charges on gains? Yes, the 7.5% solidarity levy. The CSG and the CRDS, 11.1 points on gains and dividends, are not owed. With the 12.8% of income tax, the flat tax of someone insured under the LAMal is 20.3% in 2026, against 31.4% in the French scheme.
Can the choice between LAMal and CMU be changed later? No, the droit d'option cannot be undone. The three-month window runs from the start of work in Switzerland, or from returning to work after unemployment, settling in France or retiring (CLEISS).
What does the gain on a PEA over five years old cost under the LAMal? 7.5% of the gain, the solidarity levy alone, since a PEA's gains are free of income tax after five years. In the French scheme, 18.6%.
Is the 2nd-pillar capital affected? Yes: 6.75% under the LAMal, 15.85% in the French scheme, because the CSG, CRDS and Casa on pensions, 9.1% at the standard rate, are owed only by someone covered by the French health insurance.
This article is informational and is not personalised tax advice. The rates are those of 2026, read on 16 October 2026. For a particular situation, a tax adviser who specialises in cross-border workers remains the reference.