Telework Tracker"I'm allowed 34 days" and "I'm allowed one telework day a week" are two sentences you hear in the same conversations, from the same people. They belong to two distinct legal systems, with different units of measurement and different consequences.
Confusing them is the single most common cause of unpleasant surprises for Belgian residents employed in Luxembourg.
Both thresholds at a glance
- Tax threshold (where your pay is taxed)
- 34 days / calendar year
- Default social threshold (EU rules)
- < 25% of working time
- Social threshold with framework agreement
- < 50% of working time
- Framework agreement applicable since
- 1 July 2023
- Signatories (2026)
- 23 EU/EEA states + Switzerland
- Supporting document
- Portable document A1
- Validity
- 3 years maximum, renewable
Two counters, two logics
The first counter answers: who taxes your salary? It comes from the double taxation treaties — a bilateral text between Belgium and Luxembourg. Its unit is the day.
The second answers: which social security system are you affiliated to? It comes from EU social security coordination law. Its unit is the percentage of working time.
A day is not a percentage. Two rules, two clocks, two ways to be caught out.
The tax counter: 34 days per calendar year
For a Belgian resident employed in Luxembourg, the tolerance is 34 days of work performed outside the Grand Duchy per calendar year. Below the threshold, pay stays taxable in Luxembourg. Above it, the pay corresponding to days worked outside Luxembourg becomes taxable in Belgium — and not just the excess portion.
The count is strict: any fraction of a day counts as a full day, and business trips and training outside Luxembourg consume quota. The detail is covered in our article on the June 2026 circular.
The social counter: 25% by default, under 50% with the framework agreement
The baseline EU rule is simple: if you carry out 25% or more of your activity in your state of residence, you fall under that state's social security system — regardless of where your employer is established. For a Belgian cross-border worker, that means shifting to the Belgian system, with different contributions for employer and employee alike.
Since 1 July 2023, an EU framework agreement on cross-border telework allows that limit to be pushed back. Where it applies and an application has been filed, telework can reach less than 50% of total working time while affiliation stays in the employer's state — Luxembourg in our case.
Twenty-three EU/EEA states plus Switzerland have signed it, including Belgium, Luxembourg, France and Germany. It only applies if both states involved are signatories.
The framework agreement is not automatic. Without an application and a matching A1 document, the 25% threshold remains the reference — even if both countries have signed.
Side by side
| Criterion | Tax side | Social security side |
|---|---|---|
| Source | Belgium–Luxembourg treaty | EU regulation + framework agreement |
| Unit | Days | % of working time |
| Limit | 34 days / year | < 25% (or < 50% under the agreement) |
| Fraction of a day | Counts as 1 full day | Counted as actual time |
| Business trips | Count | Treated separately from telework |
| Prior formality | None | Employer application + A1 document |
| Effect of exceeding | Taxable in Belgium from day one | Affiliation shifts + contributions regularised |
| Who bears the cost | Mainly the employee | Employer and employee |
How to apply for the framework agreement
The step belongs to the employer, not the employee:
- The employer files the application with the competent institution of the state where it is established — in Luxembourg, the Centre commun de la sécurité sociale.
- The institution issues a portable document A1, certifying which social security legislation applies.
- The authorisation runs for three years at most and must be renewed by a fresh application.
That document is your evidence in an audit, on the Belgian side as much as the Luxembourg one. Without it, "my employer agreed" carries no weight.
What rules you out of the framework agreement
- More than two states involved — the agreement assumes one state of residence and one employer state, both signatories.
- Telework reaching or exceeding 50% of total working time.
- Activity other than telework carried out in the state of residence — client visits, sites, prospecting.
- Several employers established in different states.
- Self-employed activity in parallel.
The third point deserves a careful read: a salesperson who teleworks from Belgium and visits Belgian clients is not only teleworking in their state of residence. The framework agreement may then not cover their situation.
The "one day a week" trap
It is the most ordinary arrangement there is, and it illustrates perfectly why both counters must be tracked separately.
Social side — 1 day/week ≈ 20% of time Compliant
Well under the 25% limit, and nowhere near the 50% of the framework agreement.
Tax side — 1 day/week ≈ 45 to 47 days/year Exceeded
About 135% of the 34-day ceiling, before counting a single business trip.
The employee is perfectly in order as far as social security affiliation goes, and clearly over on the tax side. Nothing irregular happened under employment law: the employer did grant one telework day a week. It is simply that nobody converted "one day a week" into "roughly 46 days a year".
The reverse case is just as real: an employee authorised at 45% telework under the framework agreement is socially covered — and past 100 days a year, three times the tax threshold.
Always convert a percentage into days before reasoning. 34 days is roughly 15% of a full-time working year. It is the tax threshold, not the social one, that is almost always hit first.
The counter you are missing
The social side is settled once a year with your employer. The tax side plays out day after day — that is the one an app tracks for you, with an alert before the threshold and an exportable history.
See the appFrequently asked questions
Does the 34-day threshold also apply to social security?
No. The 34 days are a tax threshold from the double taxation treaties. Social security affiliation is determined separately, based on a percentage of working time performed in the country of residence.
How much telework is allowed to stay affiliated in Luxembourg?
By default, less than 25% of working time in the country of residence. The EU framework agreement, applicable since 1 July 2023, allows up to less than 50% where the conditions are met and an application has been filed.
How do I benefit from the EU framework agreement?
The employer files the application with the competent institution of the state where it is established. It leads to a portable document A1 certifying the applicable legislation, for three years at most, renewable.
What happens if I exceed the social security threshold?
Affiliation shifts to the country of residence, with contributions regularised over the period concerned. The impact covers contributions, but also entitlements: pension, health insurance, unemployment.
Can I telework one day a week without any problem?
One day a week is roughly 20% of working time, so the social threshold is met. But it equals about 45 to 47 days a year, far beyond the 34-day tax threshold. Meeting one threshold says nothing about the other.
Will the 34-day threshold increase for Belgian cross-border workers?
The subject comes up regularly between Belgium and Luxembourg, with a scenario around 25% of working time being discussed. Nothing is settled: the protocol raising the tolerance to 34 days is recent, and Belgian authorities have signalled they want to let it take effect before opening a new negotiation.
Sources
- CLEISS — Cross-border telework in Europe (framework agreement, signatories, A1 procedure).
- Centre commun de la sécurité sociale (Luxembourg) — Telework information notice.
- Les Frontaliers — Telework in Luxembourg: rules and thresholds.
This article sets out the general framework applicable to cross-border workers. It is neither tax advice nor social security advice. Your employer and the competent institutions remain the reference for your situation.