Teleworking rules for France–Switzerland cross-border workers: the 40% telework tax agreement

The rule is deliberately simple to state and easy to get wrong in practice.

• The unit is annual working time, not days. Up to 40% of your yearly working time may be performed as telework from your home in France while the whole salary continues to be taxed under the normal rules of your canton — as if you had worked on Swiss soil.
• On a standard five-day week, 40% is roughly two days a week, averaged across the calendar year. A heavier week here and a lighter week there is fine, provided the full-year total stays at or below 40%.
• Your frontalier status is preserved. Teleworking within the 40% ceiling does not, by itself, change which country taxes your income or make you lose the frontalier regime.
• Up to 10 days of temporary missions outside Switzerland (client visits, training, conferences in France or a third country) can be counted as telework inside the 40%.

The French Treasury and the Swiss State Secretariat for International Finance describe the mechanism the same way — see economie.gouv.fr and sif.admin.ch.

The single most common mistake is treating "the telework rule" as one number. There are two, they come from two different legal instruments, and they do two different jobs.

The practical takeaway: because 40% is lower than 49.9%, the tax threshold bites first. If you plan your year around 40%, you are automatically inside the social-security limit too. Plan around 49.9% and you can accidentally break the tax rule. Always steer by the 40% number.

The 40% telework rule sits on top of an existing split in how frontalier salaries are taxed. Which canton your employer is in decides the base regime; the 40% rule simply protects it.

For the source-taxed cantons, the avenant adds a balancing payment: the employer state pays the residence state 40% of the tax it collects on the teleworked portion. The Geneva cantonal administration sets out the details, including the treatment of the 10 mission days, on ge.ch. In every case, staying within 40% keeps you in the regime you are already used to.

For readers who want the primary references rather than a summary, here is the chain of authority.

1. The base treaty is the France–Switzerland convention of 9 September 1966 (as amended) for the elimination of double taxation on income and wealth.
2. The telework framework comes from the avenant signed in Paris on 27 June 2023, which adds a permanent rule for salaried telework.
3. France published it through Décret n° 2025-838 du 21 août 2025 (JORF n° 0195 of 23 August 2025) — the full text is on Légifrance.
4. The avenant entered into force on 24 July 2025; its telework provisions apply from 1 January 2026, with earlier interpretative agreements having bridged the transitional years since 2023.

The operative wording deems telework performed within 40% of activity from the state of residence to be carried out in the employer state, keeps taxation there, and provides the 40%-of-tax compensation to the residence state. The list of conventions is indexed on impots.gouv.fr.

Crossing the line is not a fine — it is a change of tax and social status that can be costly and administratively heavy.

On the tax side (over 40%):

• The remuneration for your telework days becomes taxable in France from the first day, not just the excess above 40%.
• Any temporary mission days are pulled into the French-taxable side too.
• You lose the neutrality and face a dual declaration in both countries, with the risk of adjustments.

On the social-security side (over 49.9%):

• Your affiliation shifts to France for the whole activity.
• French social contributions apply, which are generally higher, and your employer must run a French-standard payroll for you.
• Your rights (health, pension, unemployment) are recalculated under French rules.

Because the 40% tax line is the lower of the two, most people who overshoot hit the tax consequences first. Track your telework rate across the year, not just week by week.

The new regime is enforceable precisely because it is now backed by reporting and data-sharing.

• A1 certificate (social security). To keep you insured in Switzerland while you telework, your employer must hold a valid A1 certificate, requested through the Swiss ALPS platform (Applicable Legislation Portal Switzerland). It is valid for up to three years and renewable.
• Automatic exchange of information (tax). The first exchange takes place in 2027, covering 2026 data. Swiss employers transmit, via the cantonal authorities, each frontalier's telework rate or days, gross remuneration and identifying data, which is shared with the French tax administration.
• Automatic breach detection. Because the data now flows both ways, exceeding 40% can be detected without a manual audit. The Swiss social-security position is set out by the Federal Social Insurance Office.

Practically, this means your telework days are no longer invisible. Agree a clear telework policy with your employer and make sure the days recorded match reality.

The whole regime rewards one discipline: counting across the full calendar year and leaving a margin.

1. Set a weekly baseline you can defend. Two days a week is a safe rule of thumb for a five-day schedule, but confirm it against your own contracted hours.
2. Keep a running telework log. Date, location and hours. It is your evidence if the annual rate is ever questioned in the 2027 exchange.
3. Budget your 10 mission days. They live inside the 40%, so a heavy travel year eats into your home-office room.
4. Leave a buffer. Aiming for ~35% rather than a hard 40% absorbs an unexpected week at home without any risk of tipping over.
5. Model the money before you decide. If you are weighing more home days against a possible change of tax or social status, run the numbers first.

The Net Frontalier tool from AdminLanding lets you estimate your net cross-border salary and see how the telework rules interact with your canton, so your planning starts from a real figure rather than a guess.