Subcontractor Substitution Rules

Once a contract is awarded, the subcontractors performing it are not simply interchangeable. European public procurement law and contract conditions impose rules on when a main contractor can replace a subcontractor, ensuring that the authority retains oversight of who is performing publicly funded work.

What are subcontractor substitution rules?

Article 71 of Directive 2014/24/EU establishes the framework. Where a contracting authority has exercised its right to require information about subcontractors, it must also be notified when a proposed subcontractor changes during contract performance. The authority then has the right to verify whether the proposed replacement subcontractor is subject to any mandatory exclusion ground, in the same way it can verify the original subcontractor.

In practice, substitution rules operate in two tiers:

Notification-only substitutions. For subcontractors who were not relied on to satisfy selection criteria and who were not specifically evaluated as part of the award, the main contractor is often required only to notify the contracting authority of the change (and to provide a completed declaration for the replacement). The authority reviews the replacement's eligibility but does not have a broad approval power over the commercial choice.

Approval-required substitutions. Where a named subcontractor was relied on to satisfy a selection criterion (for example, their specialist certification or sector experience) or was individually evaluated as part of the award criteria, the contracting authority has a stronger interest. The authority may require that the replacement firm meets equivalent qualifying standards before approving the substitution. If it does not, the authority may refuse to accept the substitution.

A mandatory substitution also arises where the authority discovers, after award, that a subcontractor is subject to a mandatory exclusion ground. In this case, Directive 2014/24/EU requires the contracting authority to demand that the main contractor replace the subcontractor.

UK position. The Procurement Act 2023 requires contracting authorities to publish a contract change notice where a material change is made to a contract. Replacing a subcontractor who was named in the contract documents or who was evaluated as part of the award is likely to constitute a material change requiring publication.

Contract modification limits. Subcontractor substitution must also be read alongside the rules on substantial contract modifications under Article 72 of Directive 2014/24/EU. Where a proposed substitution would effectively change the economic balance of the contract, or would have resulted in a different award decision had it been known at the time, it may constitute an unlawful modification requiring a new procurement.

Why it matters for bidders

For main contractors, the substitution rules mean that post-award subcontractor management requires more than a commercial decision. Any change to a subcontractor that was disclosed to the authority must be notified, and some changes require advance approval. Substituting a subcontractor without the required notification is a contract breach that can expose you to damages, suspension, or termination.

For subcontractors, the rules provide a degree of contractual protection. If you were named in a bid on which the prime relied on your qualifications, the prime cannot simply drop you in favour of a cheaper alternative without the authority's involvement. You are not wholly protected (the prime retains the right to propose a substitute), but the process creates friction and scrutiny that acts as a deterrent to opportunistic substitution.

Example

A German construction company wins a hospital extension contract. It names a specialist lift installation company in its bid and relies on that company's documented experience to meet the technical selection criteria. Midway through the project, a commercial dispute arises and the prime wishes to replace the lift company. Because the original subcontractor's qualifications were part of the selection assessment, the contracting authority requires the prime to demonstrate that the proposed replacement has equivalent qualifications. The prime submits the replacement's credentials; the authority reviews them, finds them satisfactory, and approves the substitution.

Frequently Asked Questions

Must a contractor notify the authority of every subcontractor change?

Only for subcontractors that were disclosed to the authority (for example, because the authority required disclosure or because the contractor named them voluntarily). If an undisclosed, low-value subcontractor is replaced, the contract conditions will determine whether notification is needed. Many contracts set a threshold: substitutions above a percentage of the contract value, or involving subcontractors performing critical elements, must be notified.

Can the contracting authority refuse a substitution that does not involve selection criteria?

In limited circumstances, yes. If the proposed replacement subcontractor is subject to a mandatory exclusion ground, the authority must refuse or require further replacement. Beyond exclusion grounds, the authority's powers over commercial subcontractor choices are narrower, though contract conditions may confer additional approval rights.

What happens if a substitution is made without authority notification?

It constitutes a breach of the notification obligation in the contract. The consequences depend on the severity of the breach and the specific contract terms. For a substitution that involved a mandatory exclusion ground, the breach is serious and may justify termination. For a technical notification failure with no substantive impact, the remedy may be a formal warning or cure notice.