You can read ten official pages about cross-border tax and still not know the only three numbers that decide your case: 30, 45 and 183. Here they are – with what sits behind them, and with the form numbers you actually end up needing.
As of 08/2026. Everything here assumes residence in France and employment in Germany. Sources at the end of the article.
First the fork in the road: two tax worlds
Almost all the uncertainty comes from two entirely different sets of rules circulating at once, with nobody saying which one is meant. There's the frontier-worker regime – a special rule in the France–Germany double taxation treaty – and there's the general case for everyone else. Three conditions decide which world you live in.
| Your situation | Where you're taxed | Which rule |
|---|---|---|
| Residence in 57/67/68 and workplace inside the 30 km zone and at most 45 days outside it | France – on the entire German salary | Frontier-worker regime of the France–Germany treaty |
| Any one of those three conditions is not met | Germany – for the days actually worked in Germany | General case: taxation in the state of activity, plus the 183-day test |
Simplified presentation of the France–Germany double taxation treaty. As of 08/2026.
The first row is the normal case for most people between Alsace and the Ortenau – and usually the gentler one financially, since French income tax on an average salary comes in below German wage tax. All the more reason to know what the status hangs on.
Conditions 1 and 2: residence and place of work
On the French side the border zone is pleasantly simple: the three departments Moselle (57), Bas-Rhin (67) and Haut-Rhin (68). Whether you live in Strasbourg right on the Rhine or down in Saint-Louis makes no difference – the whole department counts.
On the German side it works differently, in kilometres: what counts are municipalities whose territory lies wholly or partly within a 30 km zone from the border. Kehl, Offenburg and Schutterwald are clearly inside – our own location is about 13 km from the border. Lahr, Achern and Rastatt too.
Condition 3: the 45-day rule
This is the condition that most often tips the status over in practice. You may work at most 45 working days per calendar year outside the border zone. Go beyond that and you lose frontier-worker status – retroactively for the whole year, not just from day 46.
If the employment starts or ends mid-year, a pro-rata limit applies: 20% of the days actually worked, capped at 45 days. Starting in July therefore doesn't give you a full 45.
The most common question is what actually counts. The answer is pleasingly systematic: working days spent outside the border zone.
| Type of day | Counts? |
|---|---|
| A day at the office in Offenburg or Kehl | No – inside the border zone |
| Home office at home in Alsace | No – your home is itself in the border zone |
| A coworking day in Schutterwald | No – inside the border zone |
| Business trip to Berlin, Hamburg or Frankfurt | Yes |
| A working day in Paris or Lyon | Yes – outside the three border departments |
| Holiday, sick leave, public holiday, weekend | No – these aren't working days |
Principle: working days outside the border zone are counted. As of 08/2026 – confirm with the tax office in case of doubt.
The point almost nobody states: home office doesn't count
Plenty of articles treat "how many home-office days am I allowed as a cross-border commuter?" as an open riddle. In tax terms it hasn't been one for years. When you work at home in Alsace, you are working inside the French border zone – and days inside the border zone don't consume your 45-day allowance.
Good news with a catch: the real limit on home office isn't in tax law but in social security. There, 25% is the standard threshold and 49.9% applies under the framework agreement in force since 1 July 2023. So you can stay spotless on tax and still slide into the French system on social security. The two sets of numbers belong together – in detail in the health and social insurance overview and in the full worked example.
If you're not a frontier worker: the 183-day rule
Say you live in Strasbourg and work in Stuttgart. The residence fits, the workplace doesn't – Stuttgart is far outside the 30 km zone. So the treaty's general case applies: your salary is in principle taxed where you carry out the work, that is, in Germany.
The famous 183-day rule is the exception to that, and it gets misquoted a lot. It only moves taxation to the country of residence if all three conditions hold at once: you spend at most 183 days in the country of work within the relevant period, your employer is not resident there, and the cost isn't borne by a permanent establishment there. With a German employer, condition two is practically never met – which is why you pay German wage tax in this case.
If you work partly in Germany and partly in France, the salary is split – the familiar salary split. That's not a disadvantage, but it is administration: both countries want their share, and the days have to be documented cleanly.
The forms you actually need
The paperwork is manageable once you've seen it in the right order.
- Form 5011 – the frontier-worker certificate. Your French tax office confirms your status on it, your German employer files it, and no German wage tax is withheld. Without this piece of paper you pay in Germany first and reclaim it laboriously later.
- Form 2042 – the French income tax return. Everything lands here in the end.
- Form 2047 – declaration of income received abroad. Your German salary is entered here and carried over into the 2042.
- Form 3916 – declaration of foreign accounts. Every German account belongs here, even a plain salary account. The penalty for an undeclared account is €1,500 per account per year. It's the most expensive slip in a whole cross-border career.
- Elster – the German tax portal. Only needed if you have to file in Germany, for instance after a change of status or with a salary split.
The first-year cash-flow shock
Here is the warning that rarely appears in official leaflets and that regularly catches new cross-border commuters cold. In Germany, wage tax is deducted monthly from your pay – you never see it. As a frontier worker you pay in France, and your German employer naturally withholds nothing there.
France handles this through instalments debited straight from your account. But it takes time before the system knows about your new situation – and then the amounts arrive bundled. If you see your full gross salary land in your account in year one and treat it as net, you have a problem coming.
And where the place of work comes in
Everything above hangs on one single variable: where you actually worked on a given day. So the question of where your remote days happen isn't a comfort question – it's a tax and social security one.
A workspace on the German side of the Rhine has a quiet advantage here: it sits inside the border zone, so it doesn't count against the 45 days, and at the same time it is a working day in Germany for the social security percentage. For people from Alsace, Schutterwald is about 20 minutes from Strasbourg.
Frequently asked questions
Where does a cross-border commuter pay tax?
If residence (Moselle, Bas-Rhin or Haut-Rhin), place of work (a German municipality inside the 30 km zone) and the 45-day limit are all met, the entire German salary is taxed in France. If one condition drops away, German taxation applies to the days worked in Germany.
Do home-office days count toward the 45-day rule?
No. When you work at home in Alsace you are working inside the French border zone. Only working days outside the border zone count – business trips to Berlin, working days in Paris. The real home-office limit sits in social security, at 25% and 49.9%.
Does the 34-day rule apply to me?
No. The 34-day rule concerns other country pairs, not France–Germany. What applies to you is the 45 days in tax law and the 25% / 49.9% thresholds in social security.
What happens if I exceed the 45 days?
Frontier-worker status falls away for the entire calendar year, not just from day 46. Your salary is then taxed in Germany for the days worked there. Which is why it pays to document days as you go rather than reconstruct them at year end.
Do I have to declare my German bank account in France?
Yes, via form 3916 with your tax return – even if it's only a salary account. An undeclared account costs €1,500 per account per year. It's the most common and most avoidable mistake.
Takeaway
Three numbers, one form you collect from the tax office, and one account you declare – that's the core of it. The rest is documentation: if you note as you go where you worked on which day, you have both the 45-day limit and your social security percentage in view at all times. That's exactly what the home-office days calculator is for.
Official Sources
- impots.gouv.fr: am I a frontier worker? →Definition of frontier-worker status from the French side. Accessed 08/2026.
- Frontaliers Grand Est →Free advice service in the Upper Rhine – border zone, 45-day rule, forms.
- German Federal Ministry of Finance: tax treaties →Treaty texts and mutual agreement procedures Germany–France.
- Elster – the German tax portal →Only relevant if you have a German filing obligation.
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