A provisional sum is an allowance that is inserted into tender documents for a specific portion of the works that lacks detail for tenderers to accurately price.
As the design progresses, along with the project, the contactor will eventually be able to provide a fixed price that replaces the provisional sum allowance.
There are two types of provisional sum: defined and undefined:
- 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. An example could be ironmongery to doors where the scope is known but the exact specification and manufacturer’s reference is unknown.
- Undefined provisional sums are less well described and so the contractor cannot be expected to make allowance for them in their programming, planning and pricing preliminaries. This means the contractor may be entitled to an extension of time and/or additional payments when the actual works are undertaken. An example could be external works but no layouts, details or specifications are available and thus is a complete unknown.
When describing a provisional sum it should contain: the nature of the works, its location, the quantity and any specific limitations. If this information is not provided or available it is considered undefined.