What is a provisional sum, and how is the work valued?

The sum sits in your price as a placeholder, not a promise of payment. Nothing is due against it until your main contractor instructs the work. Once it does, the work is valued under your subcontract's valuation rules, much as a variation is. The allowance comes out of the account and the valued work goes in, so the final figure can be higher or lower. Many contracts split provisional sums into two kinds. A defined provisional sum describes the work well enough for you to plan and price around it. An undefined one does not. The difference matters for your money. With a defined sum, you are usually treated as having allowed for its effect at tender. That covers its effect on your programme and your preliminaries, your site running costs. With an undefined sum, those effects can be valued in full when the work is instructed. A prime cost sum is different again: an allowance for work or goods from a named specialist or supplier. So when a provisional sum is instructed, treat it as a variation from day one. Put it on your variation register with the instruction date. Measure the work, keep daywork sheets for anything that cannot be measured, and price the effect on your preliminaries. Never let the allowance stand in the account as if it were the value of the work. Our Variation Claim service values provisional sum work under your subcontract's rules and presses it to agreement.