Submitting new plans after your bid is not 'correcting a material error' — it's modifying your offer
The Council of State rejects the emergency appeal of a design team that, after submitting its design-build offer, sent revised plans and a €40,000 price reduction to 'correct' elevation errors: such structural adjustments are a modification of the offer, not a correction of a material error within the meaning of article 34.
What happened?
The municipality of Silly launched an open procedure for a design-build contract: design and construction of the 'Les Petits Fripons' nursery for 28 children. An ambitious project with sustainability requirements (Q-ZEN, CO2 score, timber construction). The applicants — a team of seven companies centred on contractor CBD with architect WAX — submitted an offer. On 13 December 2023 the municipality requested clarification on the elevation of the planned construction relative to Saint-Pierre Street and the adjoining parking for the nursery. On 19 December 2023 the team replied: yes, we used incorrect contour lines, which wrongly introduced a crawl space beneath the building. The crawl space could be removed, yielding a €40,000 saving on the shell construction. Attached: revised plans and schemas with the correct contour lines and without the crawl space. On 18 January 2024 they gave their oral presentation to the municipality — using the revised plans, even though the specifications (art. A3.54) required the presentation to be 'strictly limited to information included in the offer'. On 13 February 2024 the municipality declared their offer substantially irregular (art. 76 of the 2017 Royal Decree) and awarded to a competitor. The team went to emergency proceedings at the Council of State with three grounds — including the argument that this was not an offer modification but merely 'simple information', and alternatively that it was a material error recoverable under art. 34. The Council of State rejects both readings prima facie. First: the applicants acknowledge in their own 19 December letter that they had used the wrong contour lines; they supply revised plans AND a price adjustment, and then use those revised plans in their presentation. That is plainly an offer modification, not mere information. Second: article 34 only permits the correction of 'arithmetic or purely material errors', and it must be strictly interpreted as a derogation from the principle of immutability of offers. Modifying the appearance and load-bearing structure of a building in the plans of a design contract is not the correction of a purely material error — it is a genuine modification of the offer. The third ground likewise fails. Emergency application rejected, procedural indemnity of €770 charged to the applicants.
Why does this matter?
Design-build contracts put enormous pressure on design teams: you must submit a detailed proposal including price on the basis of specifications that sometimes leave interpretation room. When, after submission, you discover you've made a fundamental error — wrong terrain elevations, wrong standards, outdated materials list — the temptation to 'administratively fix it' is strong. This judgment confirms that this route is closed for substantive errors. The distinction between a 'material error' (correctable) and a 'modification' (irregularity) is crucial: material errors are typographical, arithmetic or transcription errors where the bidder's intent is evident from the rest of the offer. Correcting structural elements — plans, structures, items — is not a material error, even if you call it 'simple information'. Nor may you show altered information during an oral presentation if the specifications prohibit it. For contracting authorities this judgment confirms that you stand firm when clarification answers bring in materials that modify the offer: you can then reject the offer as irregular.
The lesson
If, after submission, you discover your offer contains a structural error (wrong building levels, wrong materials, wrong calculation basis): think twice before sending revised plans or specifications. Article 34 of the 2017 Royal Decree only covers arithmetic and purely material errors — not conceptual modifications. If the design itself is wrong, there is no rescue: your offer is what it is, and fixing it leads to irregularity. And for oral presentations: show only information that is in your submitted offer. Even if no one comments during the presentation, using modified material is grounds for exclusion.
Ask yourself
Did you send a letter after submitting your offer that contains more than an answer to a question — for instance updated plans, a price reduction or a structural rethink? Then you are in the grey zone between 'clarification' and 'modification'. Ask yourself: do my documents change the appearance, structure, quantities or pricing of what I originally submitted? If yes: it is a modification and your offer is irregular.
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 →