The principle behind tax treaties is simple: a salary is taxed where the work is physically carried out. For a cross-border worker employed in Luxembourg, every day spent working elsewhere — at home, travelling, in a third country — therefore falls in principle to their country of residence. The tolerance is the exception that makes that principle liveable: a number of days per year that may be worked outside Luxembourg without changing anything about the taxation.
34 days for all three neighbouring countries
The three treaties arrived at the same figure, but not at the same time.
Belgium. The tolerance was 24 days; the protocol signed on 31 August 2021 raised it to 34 days, applicable from income year 2022.
France. The 2018 treaty provided for 29 days; the protocol of 7 November 2022 aligned the tolerance at 34 days, applicable from tax year 2023.
Germany. The tolerance was 19 days; the protocol of 6 July 2023 raised it to 34 days as of 1 January 2024.
The figure is the same, but each tolerance lives in its own treaty, with its own counting rules. In case of doubt, the text applicable to your country of residence is what governs.
What counts as a day
The rule that surprises most: a fraction of a day counts as a whole day. A video call taken from home before setting off, an afternoon at a Belgian client's site — the day is counted, even if most of it happened in Luxembourg.
Days counting against the tolerance are those on which any professional activity, however small, is carried out outside Luxembourg territory:
- working from home, even partly;
- business travel in the country of residence;
- assignments in a third country — a trade fair in Paris, a training course in Frankfurt count too.
Not counted: holidays, public holidays, weekends not worked, sick leave, and the commute itself — travelling is not carrying out an activity.
A ceiling, not a budget
The tolerance is not an allowance to be "spent" serenely down to the last day. It is a tipping threshold: as long as you stay at 34 days or below, the whole salary remains taxable in Luxembourg; on the 35th day the logic reverses — and not only for the days in excess. That mechanism has an article of its own, but the practical consequence fits in one sentence: the last days of the tolerance are expensive, and a count kept as you go beats a reconstruction in December.
Tax is not social security
These 34 days concern tax only. Social security — the scheme you belong to, the one that pays for care and pension — follows an entirely different count, in percentage of working time rather than in days. The two counters cross without seeing each other: you can be compliant on one and not on the other. The social count has its own article too.