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Last edited 05 Sep 2018
A provisional sum is an allowance (or best guess), usually estimated by a cost consultant, that is inserted into tender documents for a specific element of the works that is not yet defined in enough detail for tenderers to accurately price.
In the case of Midland Expressway Ltd v Carillion Construction Ltd & Others, Court of Appeal Civil Division, 15 June 2006, Lord Justice May suggested that:
The term 'provisional sum' is generally well understood in the construction industry. It is used in pricing construction contracts to refer either to work which is truly provisional, in the sense that it may or may not be carried out at all, or to work whose content is undefined, so that the parties decide not to try to price it accurately when they enter into their contract.
A provisional sum is usually included as a round figure guess. It is included mathematically in the original contract price but the parties do not expect the initial round figure to be paid without adjustment. The contract usually provides expressly how it is to be dealt with. A common clause in substance provides for the provisional sum to be omitted and an appropriate valuation of the work actually carried out to be substituted for it. In this general sense, the term 'provisional sum' is close to a term of art but its precise meaning and effect depends on the terms of the individual contract.
As provisional sums are replaced by valuations of the work actually done as the project progresses, the contract sum may increase or decrease. In addition, depending on the degree to which the works that the provisional sum relates to can be defined at the tender stage, the actual works that are undertaken may affect the contractor’s programming, planning and pricing preliminaries:
Defined provisional sums are those which have been described in sufficient detail that the contractor is expected to have made allowance for them in their programming, planning and pricing preliminaries.
- The nature and construction of the work.
- A statement of how and where the work is fixed to the building and what other work is to be fixed thereto.
- A quantity or quantities that indicate the scope and extent of the work.
- Any specific limitations and the like.
Provisional sums are provided for in different ways in different forms of contract, and some forms of contract can be a little vague about how provisional sums should be handled, in particular regarding adjustments to the programme. There may also be issues if the employer decides to omit work related to a provisional sum from the contract, as the contractor may claim for loss of profit, unless the contract allows the work to be omitted. It is important therefore that parties to the contract familiarise themselves with the exact wording and meaning of the relevant clauses that are being used.
For these reasons, provisional sums should only be used as a last resort, they should not be an easy fall-back position for consultants when designs are incomplete or information is difficult to obtain. The risks are significant enough that the NEC Engineering and Construction Contract (NEC3) does not have any allowance for provisional sums.
 Find out more
 Related articles on Designing Buildings Wiki
- Prime cost sum
- The difference between a prime cost sum and a provisional sum
- Preliminaries in construction
- Provisional quantity
- Bill of quantities BOQ
- Prime cost in construction contracts
- Contingencies in construction
- Lump sum contract
- Prime cost price
- Tender documentation for construction projects
- Procurement route
- Architect's instruction
- Midland Expressway Ltd v Carillion Construction Ltd & Others
- Attendance for construction
- Contract sum
- Variations in construction contracts
- New Rules of Measurement
- Cost vs price
- Defined provisional sum
- Construction contract
- Dayworks in construction
- Nominated sub-contractor
- Approximate bill of quantities
 External references
- Expressway Ltd v Carillion Construction Ltd 2006 - the meaning of provisional sum.
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