Discount for multi-lot award? Then you must rank three times — not once
The Council of State suspends Idelux's award of nine waste-collection lots to Remondis because the intercommunal compared all offers against a single reference point (Remondis with discount) instead of ranking each scenario separately — a calculation error that shifted the outcome in Remondis's favour.
What happened?
Idelux Environnement, a Luxembourg-province intercommunal, issued a tender in February 2023 for door-to-door collection of household waste (organic and residual) across 55 municipalities, divided into 11 lots, for 8 years. Four offers. Belcyco offered a -1% discount for awarding two or more lots. Remondis offered a -10% discount conditional on receiving all of lots 1 through 9 together. The 31 March award gave lots 1-4, 6, 8, 9 to Remondis; 5, 7 to Belcyco; 10, 11 to Dureco. Remondis filed for extreme urgency under article 87 §1 paragraph 5 of the Royal Decree of 18 April 2017, which requires the contracting authority to choose the lot combination economically most advantageous for itself. Idelux withdrew its 31 March decision and on 16 May 2023 issued a new one: lots 1-9 to Remondis, 10-11 to Dureco. Belcyco received nothing and filed its own extreme-urgency application. The Council of State scrutinised the math. Idelux had assigned the maximum price points to 'Remondis with discount' for each lot and rated all other offers (including Remondis without discount) against that reference. Critical error, says the Council: 'Remondis with discount' only exists as an outcome if Remondis actually wins all 9 lots. The scenario where Belcyco wins some lots logically excludes 'Remondis with discount' as the highest reference. For lot 3 specifically: under Idelux's single ranking, Remondis-with-discount scored 975 points, Remondis-without 897, Belcyco-with 810, Belcyco-without 802. But scenario-by-scenario comparison yields different reference prices and substantially smaller gaps. Belcyco argued (correctly) that the authority should have ranked separately: (1) both without discount, (2) Remondis with discount + Belcyco without, (3) Remondis without + Belcyco with, then determined the most advantageous combination. The Walloon guidance for 'Marchés publics à lots' confirms this approach. The Council agreed: by maintaining a single ranking with Remondis-with-discount as universal reference, Idelux distorted the comparison. Idelux argued the balance of interests: the current contract expires 31 December 2023; a suspension would jeopardise waste collection for 17 weight-taxing municipalities. The Council rejected this: (1) the documents do not show absolute impossibility of extending the current contract — current operator Remondis had offered an extension with the only caveat that 100% weighing could not be guaranteed 'compte tenu de l'âge des camions'; (2) only 17 of 55 municipalities are affected; (3) Idelux had previously turned around a new procedure in three months, leaving room before 31 December 2023. Suspension of award of lots 1-9 to Remondis. Lots 10-11 to Dureco stand.
Why does this matter?
Multi-lot tenders with combination discounts are a calculation trap that even experienced contracting authorities fall into. The simple method — 'take the best price as reference and rate all others against it' — works without conditional discounts. The moment a discount depends on a specific lot combination, parallel scenarios appear: in scenario A discount X applies, in B discount Y, in C no discount at all. Each scenario has its own 'best price', which must serve as reference for offers within that scenario — not for the whole tableau. A single central reference distorts the comparison and leads to the wrong choice of economically most advantageous combination.
The lesson
For multi-lot contracts with combination discounts: rank scenario by scenario. Identify all possible award scenarios (and their associated discounts), compute scores within each scenario per the specifications method, and only then compare scenarios to choose the combination economically most advantageous to the authority. Document each scenario in your evaluation report and explain why the chosen scenario outperforms alternatives where multiple bidders win lots. The number of scenarios grows exponentially with lots — use a spreadsheet or script to avoid skipping any.
Ask yourself
In your evaluation report, did you separately compute price scores for every award combination, with the correct 'best price' as reference within that scenario? Did you explicitly include 'both without discount' when no combination discount applies? Can you explain why your chosen award is economically better than every alternative scenario, not merely better than the one you accidentally used as universal reference?
About this database
The Council of State (Raad van State / Conseil d'État) is Belgium's supreme administrative court. In disputes over public procurement — from contract awards to tenderer exclusions — the Council of State is the final arbiter. The rulings in this database are summarised by TenderWolf in plain language, with practical lessons for tenderers and contracting authorities. View all rulings →