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The Proportionality Guide limits requirements on references, turnover and consortia. This is how you recognise a requirement that is out of proportion.
Checked on 15-09-2026
According to PIANOo, the Proportionality Guide (Gids Proportionaliteit) is a mandatory guideline under the Dutch Procurement Decree, covering the whole tender procedure. It applies to European, national and multiple private tenders. The version on PIANOo is the third revision, dated 1 January 2022. If an authority deviates from its rules, it explains that choice in the tender documents.
For companies with 10 to 250 employees, the rules on requirements matter most. On references, rule 3.5 G says: the contracting authority asks for at most one reference per named core competence, and does not require reference projects to have a value of more than 60% of the estimated value of the contract. The Guide gives the example of a municipality that does not require a bidder to have designed the same building three times before, but lets the bidder choose references that show the required competence.
On turnover, the rule is that in principle no turnover requirement is set. If an authority does set one, it justifies this with weighty reasons and the requirement is no higher than three times the estimated value of the contract or of the lot. Under rule 3.5 H, the contracting authority sets no higher requirements for consortia of bidders than for a single bidder.
The size of the contract itself also falls under the Guide. Unnecessarily combining contracts, known as clustering, is not permitted by law, and if it does happen, the authority explains it in the tender documents. The Guide describes dividing contracts into lots as a way to give more companies the opportunity to take part and to widen the possibilities for SMEs.
What this means for you: compare the requirements in a tender with these rules before you decide to drop out. If an authority asks for a reference worth more than 60% of the estimated value, sets a turnover requirement without explanation, or has not divided a large contract into lots without giving reasons, you can raise this in the question round, citing the rule in the Guide. The authority does not have to adopt your suggestion, but a deviation from the Guide should be justified.
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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