Modifying Public Contracts: When Is a New Tender Required?

Article 72 of EU Directive 2014/24/EU codifies the case law of the European Court of Justice on contract modifications. The general principle is that a substantial modification of a public contract during its execution requires a new procurement procedure. A modification is substantial if it renders the contract materially different from the original — in effect creating a new contract that, if put to market, would attract different tenderers or different bids.

The policy rationale is straightforward: allowing unfettered contract modification would undermine the competitive procurement that gives public contracts their legitimacy. A supplier that wins a contract at a competitive price could, without this rule, agree a series of variations that transform the contract into a fundamentally different and much more valuable arrangement that other suppliers would have competed keenly to win.

Article 72 sets out five categories in which modifications are permitted without re-procurement. First, modifications provided for in the initial procurement documents in clear, precise and unequivocal review clauses — including price revision clauses, option clauses and extension clauses. Second, additional works, services or supplies from the original contractor where a change of contractor cannot be made for economic or technical reasons and would cause significant inconvenience or substantial duplication of costs. Third, modifications necessitated by circumstances that a diligent authority could not have foreseen. Fourth, where the modification is not substantial as defined in the Directive. Fifth, a succession of a new contractor following restructuring, insolvency or acquisition of the original contractor, provided selection criteria are met.

For the second category (unforeseen circumstances), the modification value must not exceed 50% of the original contract value. For the third category, the same 50% cap applies and the modification must be documented with evidence of the unforeseeable circumstances. These categories are narrow exceptions to the general rule and should be applied with corresponding caution.

Article 72(4) defines a modification as substantial if it introduces conditions which, had they been part of the initial procurement, would have allowed for the admission of other tenderers or for the acceptance of a different tender; changes the economic balance in favour of the contractor; extends the scope of the contract considerably; and (where a new contractor replaces the original) the change was not provided for in the original contract.

A quantitative safe harbour exists: a modification that does not exceed 10% of the original contract value for services and supplies, or 15% for works, is presumed not to be substantial — provided the modification does not alter the overall nature of the contract. Authorities should note that this safe harbour is cumulative across multiple modifications: if the combined value of all modifications to a contract exceeds the threshold, the safe harbour no longer applies to the later modifications even if each individual modification was within the percentage.

For CWMF public works contracts, the modification rules interact directly with the variation regime under Clause 10 and the threshold tests in the GovIQ Threshold Engine. The CWMF's 50% statutory variation ceiling (Threshold T4) aligns with the Article 72 quantitative cap on modifications without re-procurement — exceeding 50% of the contract sum in variations generally requires a new tender, unless one of the specific Article 72 exceptions applies.

Authorities managing active construction contracts should monitor cumulative variation values against both the CWMF thresholds (which trigger governance and approval requirements) and the Article 72 thresholds (which trigger re-procurement risk). GovIQ's Threshold Engine monitors both concurrently and alerts the project manager when cumulative variations approach any applicable limit, preventing the authority from inadvertently crossing into re-procurement territory without legal analysis.