Telework for cross-border workers: count your days with homeoffice.lu

Nearly one employee in two in Luxembourg lives on the other side of the border. For these French, Belgian and German cross-border workers, teleworking has become a real matter of convenience… and a real tax issue. Beyond a certain number of days worked from home, taxation and even social security affiliation can switch. So that everyone can easily track their days, we have launched homeoffice.lu, a free tool, with no registration required, available in French, German and English.

Two counters, two different rules

The main source of confusion is that there are two completely independent thresholds: one concerns tax, the other social security. You can comply with one and exceed the other.

1. Tax: the 34-day rule

The tax treaties concluded by Luxembourg with France, Belgium and Germany allow a tolerance of 34 days per year worked outside Luxembourg. Below this ceiling, your salary remains fully taxable in the Grand Duchy: nothing changes for you.

Beyond it, the tolerance falls away entirely: it is not only the excess days that become taxable in your country of residence, but all days worked outside Luxembourg, from the very first one. Exceeding the limit by just a few days can therefore have far more serious consequences than you might imagine.

Points to watch:

• A half-day counts as a full day.
• It is not only telework days that count: business trips, training sessions or professional meetings abroad are also included in the count.
• On the other hand, the following do not count: holidays, weekends and public holidays when not working, sick days and cases of force majeure.
• For cross-border workers treated as residents (tax class 2, for example), telework may also affect Luxembourg taxation itself.

2. Social security: 25% or 49.9%

On the social security side, the European principle is simple: if you carry out 25% or more of your activity in your country of residence, you may be affiliated there. Since 1 July 2023, a European framework agreement on cross-border telework, signed notably by Luxembourg, France, Belgium and Germany, allows you to telework up to 49.9% of your time while remaining affiliated to the Luxembourg social security system.

But be careful: this scheme is not automatic. Your employer must request an A1 certificate from the Common Social Security Centre (CCSS), valid for three years at most. Without a valid A1, the 25% rule applies.

In practice, for a full-time employee, 49.9% represents around a hundred days a year, well above the 34 tax days. It is therefore almost always the tax threshold that is reached first.

What homeoffice.lu does

We designed homeoffice.lu to answer a very specific question: “How many telework days do I have left this year?”

• Two-threshold calculator: you enter your country of residence and your working days outside Luxembourg, and the tool shows where you stand against the 34 tax days and the social threshold.
• The reverse case: you live in Luxembourg but work partly from abroad? A dedicated section explains the applicable rules, particularly those concerning the A1 certificate.
• Proof of your count: in the event of an audit, it is essential to be able to prove your day count. homeoffice.lu generates a summary that you can print or receive by e-mail as a PDF, with your name and your employer’s name if you wish.
• A clear FAQ covering the questions that come up most often.
• Three languages: French, German and English.

Your data stays with you

The calculation is carried out entirely in your browser. No registration is required, and your days, your name or your employer are not stored on our servers. The PDF sent by e-mail is generated on request, without retaining the information you entered.

Our practical advice

1. Keep your count up to date as you go, rather than at the end of the year: it is much easier to correct course in October than in December.
2. Keep your evidence: calendar, badge records, expense reports, correspondence with your employer.
3. Put your telework arrangement in writing with your employer, and check that an A1 certificate has been requested if you exceed 25%.
4. Don’t forget business trips: a two-day training course in Metz, Arlon or Trier counts too.
5. If in doubt, seek advice: exceeding the limits can have significant consequences for your tax liability.

The two free homeoffice.lu apps: iPhone and Android

The simplest approach is to count your days as you go. That's why homeoffice.lu also exists as free apps for iPhone and Android. Your telework counter is always in your pocket: a day at home, a training course abroad, a trip to a client — you log it in a few seconds and always know where you stand relative to the 34 tax days and the social security threshold.

• Free, in French, German and English.
• Your day-by-day count, instead of a laborious reconstruction at year-end.
• Both thresholds at a glance: tax (34 days) and social security (25% / 49.9%).

Why does a real estate agent care about telework?

Since 2006, iMMOSOLUTIONS has been supporting buyers, sellers and tenants on both sides of the border. The choice between living in Luxembourg or in a neighbouring region increasingly depends on how many days you can spend at home — and on their tax consequences. homeoffice.lu follows the same logic as our other free tools, such as stop.lu: providing clear answers to concrete questions.

👉 Calculate my telework days on homeoffice.lu
📱 homeoffice.lu app for iPhone · for Android — free

The information in this article is provided for indicative purposes only and does not replace personalised tax or legal advice. The thresholds mentioned are those in force as of October 2026.