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Which past contracts count as references, how far back and which limits the Proportionality Guide sets.
Checked on 15-09-2026
References show that you have already carried out comparable work well. The Dutch Public Procurement Act 2012 lists them as evidence of technical and professional ability (article 2.93). For works, this means a list of works from a period of at most the last five years, with certificates that the most important works were properly carried out. For supplies and services, it means the main contracts from at most the last three years, with amount, date and client. PIANOo indicates that a longer period is allowed only where the particular circumstances of the contract justify it.
The Act refers to public or private clients. Work for companies can therefore also serve as a reference; you do not need to have worked for a public body before.
The Proportionality Guide limits what an authority may ask. The authority sets core competencies that match the essential parts of the contract (rule 3.5 F). It asks for at most one reference per core competency, and a reference project need not exceed 60% of the estimated value of the contract (3.5 G). The Guide also calls for restraint in formal requirements for references, such as a newly signed form from the same client every time.
If you lack experience in one part yourself, you can rely on another company, which then fills in its own ESPD, or bid as a consortium. A consortium may not be given heavier requirements than a single bidder (3.5 H).
What this means for you: build a reference file now, before you see a tender. For each project, record the client, the contact person, the period, the amount, a short description and which competency the project demonstrates. Ask satisfied clients in advance whether you may name them as a referee. In a tender, choose for each requested core competency the project that comes closest to it.
These articles explain how public tendering works; they are not legal advice. If you are unsure about a specific tender, ask your question through the clarification round or consult a lawyer.
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