Before you start

A French tax number, issued after your first declaration
Records of worldwide income for the year, including any German salary
A record of days worked outside the border zone, if you commute to Germany
Credentials for impots.gouv.fr, once you have a number

Step-by-step

1
Establish whether the frontier-worker regime applies to your German job
It requires that you live in the French border zone — for these purposes, the departments of Bas-Rhin, Haut-Rhin and Moselle — and that you work in a German commune lying wholly or partly within 30 km of the border, returning home as a rule each day. If you meet it, the salary is taxable in France and not in Germany.
OnlineWho: YouBefore starting the job
2
Get the exemption certificate to your German employer
Without the certificate confirming frontier-worker status, your German employer will withhold German wage tax as normal and you will be reclaiming it. The document is form 5011, completed by you and your employer and validated by your French tax office before it goes to the German tax office covering the company. Do this before the first payroll run rather than afterwards.
Via employerWho: You and your employerBefore the first payslip
3
Count your days outside the zone, because 45 is the limit
You may work outside the border zone, or not return home, on up to 45 days a year without losing the status. Working from home inside the border zone does not count against that limit. Exceeding it costs you the regime for the whole year, so keep a calendar rather than an impression.
OnlineWho: YouContinuously
4
Understand that social security follows Germany even when tax follows France
The frontier-worker regime is a tax rule. Social security under EU coordination follows the place of work, so a German employer means German contributions, a German sickness fund and German pension rights, with a portable document registering your entitlement to be treated in France. The two systems answer different questions and give different answers.
Via employerWho: You and your employer
5
File the French declaration and report the German income
Report the German salary on the appropriate schedule. If the frontier regime applies, it is taxable in France in the ordinary way. If it does not, Germany taxes it and France relieves the double taxation while still taking the income into account for the rate applied to the rest of your household's income.
OnlineWho: YouSpring annually
6
Declare every foreign account, including any German one
French tax residents must list all foreign bank accounts, life insurance contracts and digital asset accounts annually, whether or not they generated income. A German salary account is exactly the kind of account people forget because it feels local.
OnlineWho: You

Documents you’ll need

French tax number, once issued
German payslips and annual employer statements
The frontier-worker exemption certificate validated by the French tax office
A calendar of days worked outside the border zone
Marriage or PACS documentation, for household parts

Things most newcomers don’t know

Unlike Lille and Belgium, the France–Germany frontier-worker regime is alive — but it is conditional and it is checked.

Live in Bas-Rhin, Haut-Rhin or Moselle, work in a German commune wholly or partly within 30 km of the border, and return home as a rule each day, and your German salary is taxable in France rather than Germany. That is a materially different answer from the one a French resident working in Belgium gets, and it is one reason Strasbourg and Lille are not comparable cross-border cities. The conditions are specific and the status is assessed annually.

Source: convention fiscale franco-allemande

The 45-day limit is the thing that catches people, and telework at home does not count against it.

You can spend up to 45 days a year working outside the border zone, or not returning to your French home, before frontier status is lost for the whole year. Business travel to a client in Berlin, a training week in Munich and a conference in Hamburg add up faster than people expect. Working from your own home inside the border zone is not counted, which is a genuinely favourable rule — but only if you know where the line falls.

Source: Frontaliers Grand Est / convention fiscale franco-allemande

Without the exemption certificate, your German employer withholds German tax anyway.

Frontier-worker status does not apply itself. The employer needs a certificate, validated by the French tax office, releasing them from German wage tax withholding. Start work without it and German Lohnsteuer comes out of every payslip while you are also liable in France, and unwinding that is a reclaim procedure rather than a correction. Get the paperwork done before the first payroll run.

Source: impots.gouv.fr / Frontaliers Grand Est

The droit local changes a great deal in Alsace, but it does not change your income tax.

Local law here governs health cover, public holidays, Sunday work, land registration, personal insolvency and sick pay. It does not create a regional income tax or alter the national scale — France, unlike Spain, has no regional income tax component at all. Newcomers who have read about droit local sometimes assume there is a local tax dimension to find. There is not; the tax questions worth your time are the household quotient and, if you work in Germany, the frontier regime.

Source: impots.gouv.fr / Institut du droit local

Common mistakes to avoid

Starting a German job without the exemption certificate and having German wage tax withheld.
Losing frontier status by quietly exceeding 45 days outside the border zone.
Assuming the tax rule and the social security rule give the same answer — they do not.
Not declaring German income in France because you believe the regime handles it invisibly.
Failing to declare a German bank account on the French foreign accounts form.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.