What is subcontracting on site
Subcontracting is the legal transaction by which a company, the subcontractor, agrees to execute part of the work or a service that was originally hired to another company, the contractor, by the developer. The contractual relationship thus remains at two levels: the main contract between developer and contractor, and the subcontract between contractor and subcontractor, each with their own obligations.
In the Spanish construction sector, this figure is specifically regulated by Law 32/2006, of October 18, regulating subcontracting in the Construction Sector, a law designed to limit excessively long subcontracting chains and ensure that each company involved in the work meets minimum solvency and prevention requirements.
How the subcontracting contract is formalized
The law requires that the subcontracting contract is always formalized in writing, detailing the object of the contract, the conditions of execution and the obligations of each party. A verbal agreement, however clear it may seem between the parties, does not meet the legal requirement and leaves the contractor without the documentary traceability that the law itself seeks to guarantee.
The contract must include the complete data of both companies, company name, Tax ID, registered address and legal representative, and in the case of the subcontractor, their registration number in the Register of Accredited Companies (REA) and their Social Security registration number. Without these data, the contract is incomplete even if the parties have already started working.
Requirements before contracting a subcontractor
Before signing the subcontract, the contractor should verify that the subcontracting company is registered in the REA and that its certificate is still valid, that it has the required prevention coverage for the work it will execute, and that it is up to date with its Social Security obligations, non-payment of a subcontract can transfer responsibility to the main contractor in certain cases.
Checking this before contracting is cheaper than discovering it after the subcontractor is already working on site: reversing access already authorized creates friction with the team and delays that prior verification would have prevented.
Permitted levels of subcontracting in the chain
Law 32/2006 limits the number of subcontracting levels allowed on a project, generally up to the third level, to prevent opaque chains where it is impossible to verify who actually executes each item and under what conditions. Each additional level of subcontracting must be justified and is subject to the same accreditation requirements as the previous level.
On site, keeping a record of at what level each company is in the chain, not just its name and contact, is what allows you to check at a glance whether subcontracting stays within the legal limit or has already exceeded it without anyone noticing.
What should be monitored during subcontract execution
Once the contract is signed, control does not end: it is advisable to monitor the validity of the subcontractor's REA certificate, modifications or scope expansions agreed upon as you go (which should be documented like the initial contract), and agreed payment deadlines, especially if the main contractor itself is subject to payment deadlines to the developer.
A subcontract without active monitoring tends to create the same problem on site: verbal changes that no one documents, and that are later difficult to reconstruct when a discrepancy arises about what was actually agreed.
Common errors when managing subcontracting
The most common errors are: granting access to a subcontractor before verifying their valid REA certificate, accepting verbal scope expansion agreements without leaving written record, not reviewing whether the subcontracting chain has exceeded the permitted level, and treating subcontractor documentation as a one-time procedure rather than a control that must remain valid throughout the work.
None of these errors is exclusive to large projects: on a small project with two or three subcontractors, the lack of monitoring goes unnoticed for longer precisely because there is less volume to make it evident.
How Bloqbase supports subcontractor management
Bloqbase can help maintain in one place the data of each subcontractor registered on the project, REA certificate validity, level in the subcontracting chain, documentation associated with the contract, instead of spreading them across folders and loose emails.
The software does not replace the drafting of the contract or legal advice on its content: the responsibility to formalize the subcontract in writing and verify the legal requirements of each subcontractor remains with the main contractor.