The threshold for price investigations is fixed: you can't simply raise it
If the specifications state that bids deviating more than 15% from the average must undergo a price investigation, you may not set that threshold at 25%, even to check deviations 'in both directions'.
What happened?
The City of Brussels tendered a works contract for road construction. The specifications themselves stated: whoever is more than 15% above or below the average gets a price investigation. However, the contracting authority worked with 25% instead of 15%. Three bids passed through, including the cheapest (which was chosen). The loser received a price investigation due to the 25% threshold. With the statutory 15% threshold, the cheapest bid would also have been questioned. The Council of State found: you may not simply raise the statutory threshold in your specifications.
Why does this matter?
This is about formal equal treatment. The rules must apply to everyone. When a contracting authority raises the threshold, it creates unequal treatment. This also affects trust: if tenderers see that rules change on the spot, they lose confidence in the process. The rule is now: stick to 15% unless you have legally justified reasons.
The lesson
Read the specifications extremely carefully regarding thresholds and criteria. Check whether those thresholds are legally correct — is 25% really permitted or not? If you have doubts, challenge it. A threshold that has simply been raised can infect an entire procedure.
Check yourself
Have I critically read the thresholds and deviation percentages in the specifications, and am I sure they are legally correct?