Design verification and validation: what they check on cost

Three paragraphs of art. 42 of the public contracts code set out the essentials. The current version has been in force since 1 April 2023.

Verification takes place during design, not at the end. The contracting authority verifies that the design matches the documento di indirizzo alla progettazione (design brief, DIP) and complies with the rules in force while the design is being developed (Legislative Decree 36/2023, art. 42(1)). In a design-and-build contract (appalto integrato), the progetto di fattibilità tecnico economica (technical and economic feasibility design, PFTE) is verified before the award procedure starts, and the detailed design prepared by the successful bidder before the works begin.

Verification is an exchange between the parties, overseen by the RUP. It takes place as an exchange between the verifier and the designer, and the RUP oversees it (para. 2). The same paragraph sets out the incompatibility: for the same design, verification cannot be carried out by whoever handled the design, safety coordination, works direction or testing and acceptance.

Validation is the formal act that closes the process. It takes up the results of verification, is signed by the RUP, and the contract notice states its reference details (para. 4). A design that has not been validated should not go to tender.

Stage	What happens	Who	Outcome for the budget
During design	Verification of compliance with the DIP and the rules	Verifier, in an exchange with the designer, overseen by the RUP	Gaps identified while the design can still be changed
Before the tender	Validation of the design to be used as the tender basis	RUP	Estimate and economic summary adopted as the basis of the procedure
Design-and-build contract	Verification of the PFTE before the procedure, of the detailed design before the works	Contracting authority	Double check: on the design put to tender and on the successful bidder's design
Contract notice	Statement of the validation reference details	Contracting authority	Traceability of the economic basis of the tender

Verification is not an accounting check, but it touches cost at three points. The first is compliance with the economic limits: the design brief states "the economic limits to be respected and any indication of the financial cover for the works" (Annex I.7 to Legislative Decree 36/2023, art. 3(g), unofficial translation). Verifying that the design matches the DIP therefore means, in the logic of the rule, also verifying that the estimate sits within those limits, or that the gap has been acknowledged and covered by an explicit decision.

The second is the presence of the economic documents. For the technical and economic feasibility design, the documents include the "estimate of the works" and the "economic summary of the project" (Annex I.7, art. 6(7)(i) and (l)). For the detailed design, unless the contracting authority determines otherwise with reasons, they include the programme, the list of unit prices with the analyses, the computo metrico estimativo (priced bill of quantities) and the quadro economico (economic summary), the draft contract and the special specification (art. 22(4)(h), (i), (l), (m)). The RUP may adapt the list for the PFTE by a reasoned provision in the DIP.

The third is consistency between the documents. The quantities in the priced bill must match the drawings, the prices applied must match the price schedule, the works total must match the economic summary, and the timings in the programme must match the cost assumptions. This is the check that most often brings to light missing items, prices without analysis or quantities not updated after a design change. Preparing the bill of quantities for the detailed design is covered in the dedicated guide.

After validation, the estimate becomes the basis of the tender. The estimated value of the contract is fixed when the call for competition or contract notice is sent (Legislative Decree 36/2023, art. 14(7)), on the total amount payable net of VAT (para. 4). How the tender base amount is built up is explained in the guide to the priced bill of quantities.

A gap found at verification costs a revision; the same gap found at tender stage costs a procedure. If the design put to tender is underestimated, the bids will come in above the base and the contracting authority will be able not to award only if it provided for this in the contract notice; if it is incomplete, the missing items will become modifications during the works, to be funded from the sums in the economic summary.

The exchange is an opportunity, not a formality. It is the moment when the designer explains their choices and the verifier tests them. For the contracting authority, documenting the gaps and the corrections requested at that stage is the best way to reach validation with a defensible estimate.

The RUP holds the two sides together. The RUP oversees verification and signs validation, and is responsible for the project throughout its cycle, from programming to execution (Legislative Decree 36/2023, art. 15(1)). The RUP's role on the budget is covered in The RUP and RUP support: who holds the budget of a public project.

The bodies authorised to carry out verification and the value thresholds that determine them are not described here. Art. 42(5) refers to Annex I.7 for these rules; before organising the verification of a project, the contracting authority must read the current version of the annex for the value of its own works.

Nor are the make-up of the economic summary and the build-up of prices described. They are covered in the guide to the priced bill of quantities; what matters here is only what verification checks and its effect on the budget.

A private client is not required to carry out verification, but can copy its logic. Four elements carry over easily into a private appointment.

• A reference document written before the design. The private equivalent of the DIP is a brief with a dated spending limit, written into the designer's appointment. Without a reference, there is nothing to verify against.
• A check during the design, not at the end. Providing in the appointment for an estimate to be delivered at each stage, and for a mandatory revision when the estimate exceeds the limit, is the private equivalent of verification during design.
• An independent checker. A private client can entrust the check to a third-party professional, writing into the brief the same incompatibilities as art. 42(2): no design, safety coordination, works direction or testing role on the same project. The method is described in The independent cost check.
• A signed validation. Before going out to contractors, the client signs a note accepting the design and the estimate as the basis for the award, with any remaining gap and the decision taken. It is the document that, if there is a later dispute, states the basis on which the decision was made.