Business administration
Support with day-to-day formalities, document preparation, administrative organisation and procedures related to running your company.
Ask about this serviceLuxembourg · Belgium
Your administrative partner for the construction industry in Luxembourg and Belgium.
We support construction companies with administrative procedures, document compliance and cross-border requirements.
Our services
Administrative support tailored to the needs of construction companies in Luxembourg and Belgium.
Posted workers and site compliance
Help with posting of workers: Limosa declarations, Checkinatwork, A1 documents, subcontractor files and administrative requirements in Belgium and Luxembourg.
Ask about this serviceTax, VAT and regulatory procedures
Administrative support with tax and VAT documentation, cross-border formalities, permits and documents required by the competent institutions.
Ask about this servicePDF guides and personalised support
Practical guides on formalities, documentation and procedures for construction companies. Online shop coming soon.
Ask about this serviceOur support is administrative; it is not legal or tax advice and does not guarantee any outcome with the authorities.
Why choose SONAS?
Our goal: save you time, keep your documentation better organised and help you reduce the risk of formal irregularities.
Construction specialists
We understand the administrative reality of construction companies and subcontractors.
Luxembourg and Belgium
Solid knowledge of the formalities specific to both markets.
An individual approach
For local businesses and foreign companies alike, including Polish firms.
One point of contact
A single contact for all your administrative matters.
Luxembourg & Belgium
SONAS supports companies active in both markets, including foreign businesses and subcontractors carrying out cross-border projects.
How we work
- 01
First contact
You tell us about your company and your needs.
- 02
Analysis
We review your case and define the required documents and the scope of support.
- 03
Delivery and follow-up
We carry out the agreed administrative tasks and keep you informed.
Insights & updates
All articlesConstruction in Belgium: new time-registration rules for 2027 and legal obligations for foreign subcontracting
Declaration of works to the ONSS, foreign subcontracting and planned changes to site attendance registration: the procedures to prepare for.
Read articlePosting workers to Belgium: which residence rules must be followed?
Short and long stays, EU and non-EEA workers, municipal procedures and the EES: the obligations to prepare for.
Read articleWorking legally on construction sites in Luxembourg: what you need to know!
ITM declarations, Social Badges, A1 certificates, non-EU workers, business permits and VAT: essential procedures before starting on site.
Read articleSONAS Luxembourg Sarl-S
About
SONAS Luxembourg Sarl-S is an administrative support and business management company. We help construction companies and their subcontractors keep their documentation in order and meet their administrative obligations in Luxembourg and Belgium.
Let's discuss your needs
A question about your company's administration or a specific project? Get in touch.
- officesonasluxembourg@gmail.com
- +32 471 81 35 97
- +48 695 028 727
- 9B Rue Basse, L-4963 Clemency, Luxembourg