Are you planning a construction project in Spain as the main contractor? Will you subcontract part of the work to other companies or self-employed workers without employees? Or is your company based abroad but posting employees to Spain for a construction project? In all these cases, you must comply with the obligation to maintain a subcontracting book (Libro de Subcontratación).
What is the subcontracting book?
Subcontracting involves hiring other companies or self-employed workers to perform part of a construction project. Proper subcontracting ensures legal compliance, safety, and clear responsibilities on Spanish construction sites.
The subcontracting book is an official document required in the Spanish construction sector. It must be approved by the relevant territorial Labour Office (Dirección Territorial de Trabajo y Empleo) before work begins. In the book, the main contractor must chronologically document every subcontracting agreement – both with subcontractor companies and self-employed individuals without employees. The subcontracting book must always be available on the construction site.
Obligation applies to foreign companies as well
This obligation also applies to foreign construction companies acting as main contractors in Spain. If your company is contracted to carry out construction works in Spain and posts employees for the project, you must also obtain and maintain a subcontracting book.
When is maintaining a subcontracting book required?
The subcontracting book is mandatory when:
- Your company acts as the main contractor in a construction project in Spain
- You subcontract part of the work to other companies or self-employed individuals
- You post employees from another country to Spain as the main contractor
Each construction site requires a separate, individually approved subcontracting book.
Other obligations for foreign companies
Foreign companies working on construction projects in Spain must also meet additional administrative requirements. They must submit posting notifications to the Spanish Labour Office, register in the Registro de Empresas Acreditadas (REA), appoint a representative to liaise with Spanish authorities, and ensure that all posted employees have the proper health and safety training according to Spanish law. Failure to comply may result in fines or work stoppages.
Main contractor responsibilities
The main contractor is responsible for:
- Applying for approval of the subcontracting book before work begins
- Maintaining and updating the book on-site
- Making the book available to authorities (e.g., labour inspections) on request
Benefits of maintaining a subcontracting book
- Better control over the construction site and participants
Maintaining records allows for better oversight of who is physically present on site, which is essential for safety, access management, and workflow organization. - Clear information on who is working, with what staff, and under which terms
A properly maintained subcontracting book provides immediate answers: which company is on site, how many employees, and whether they are legally employed. - Prevention of unauthorized or unqualified companies
The register reduces the risk of unapproved companies entering the site without proper contracts or insurance, enhancing both legal compliance and safety. - Reduced legal and HR risk
Proper documentation can protect the main contractor from co-responsibility in case of irregularities, such as missing employee registrations. - Compliance during inspections
The subcontracting book – especially in digital form – simplifies inspections by Labour Authorities, safety officials, or investors, demonstrating due diligence. - Transparency towards investors or clients
Maintaining a subcontractor record signals professionalism, transparency, and legal compliance, which can be an advantage in public or private tenders.
If your company operates in the Spanish construction sector or plans to start, ensure the subcontracting book is properly prepared and maintained. Remember, before obtaining the subcontracting book, you must also register in the REA.
Contact us for assistance with preparing the required documents or legally posting employees to Spain. Most documents should be prepared in advance, and some need to be uploaded to online platforms provided by the main contractor.