What Is a Provisional Sum?
A provisional sum is a placeholder, not a fixed price. Here is what it means on your quote and how to keep it under control.
The short answer
An allowance for what can't be priced yet. Settled at the real cost later.
A provisional sum is an amount included in a building quote for work or items that can't be priced accurately when the quote is written, such as something hidden until the job is opened up, or a fitting you haven't chosen yet. It is a placeholder, not a fixed price. When the real cost is known, the provisional sum is replaced with the actual figure, so the final bill can go up or down.
Provisional sums are a normal and honest way of dealing with unknowns. The thing to watch is their size and how they will be settled. The guide to provisional sums explained goes into more depth.
When they appear
Three common reasons for a provisional sum
Hidden condition
Timbers under a roof covering, the state of a wall behind plaster, or ground conditions under a new floor can't always be seen at the site visit.
Choices not yet made
If you haven't picked a finish or fitting, the contractor may include an allowance for it until you do.
Work that depends on others
Costs that rest on a third party's price or decision may be shown as an allowance until that figure is confirmed.
How it differs
Provisional sum or fixed price?
A fixed-price item
- Priced in full at the time of the quote
- Stays the same unless the work changes
- The contractor carries the risk of getting it wrong
A provisional sum
- A best allowance at the time of the quote
- Adjusted up or down to the actual cost
- You carry the difference, in either direction
Keeping control
Five questions to ask about any provisional sum
What is it for, exactly?
The quote should say what the allowance covers, not just give a figure.
How was the figure arrived at?
A realistic allowance is based on something: experience of similar jobs, a supplier's price, or a stated rate.
How will the final cost be worked out?
Agree whether it will be settled at cost, at an agreed rate, or by a separate price you approve.
Will you be told before it is exceeded?
Ask to be told, and to agree, before any provisional sum is overspent. Our answer on what happens if the price goes up covers the wider picture.
Can any of it be firmed up now?
If you can make a choice or allow an early look at a hidden area, the contractor may be able to replace the allowance with a fixed price.
Comparing quotes
Why provisional sums matter when you compare
Two quotes can treat the same unknown very differently. One contractor prices it in full; another shows a modest allowance. The second quote looks cheaper, but only until the real cost is known. When you compare, set the provisional sums side by side and ask each contractor what they expect the final figure to be. Our answer on how to compare quotes fairly explains the rest of the method.
If a provisional sum does grow, who pays depends on why. See who pays for extra work?
A quote made up mostly of allowances gives you little certainty about the final cost, however low the headline figure looks.
At the end of the job
How a provisional sum is settled
When the work covered by a provisional sum has been done, the allowance is taken out and the actual cost put in its place. If the real cost was lower, your bill goes down. If it was higher, it goes up by the difference.
It is reasonable to ask how the actual cost has been worked out: a supplier's invoice for an item, the time and materials used, or a price you agreed when the unknown was uncovered. The adjustment should be shown clearly on the final invoice, so you can see each allowance and what replaced it.
Settling provisional sums as you go, rather than all at the end, makes the final account much simpler for both of you.
For how changes to the work itself are agreed and priced, as opposed to allowances already in the quote, see variations and extra costs.
If you use Mortaro
Questions answered before you accept
If your quotation from us includes an allowance you'd like explained, ask us. We put the question to your contractor, who priced the work, and come back to you with the answer before you commit. See how quotations work.
Straight answers
Questions about provisional sums
Is a quote with provisional sums a bad quote?
No. It can be a sign of honesty about what isn't known yet. What matters is that each allowance is realistic and clearly explained.
What is a prime cost sum?
A similar allowance, usually for a specific item to be bought, such as a fitting you will choose later. It is adjusted to the actual price in the same way.
Can I ask for a provisional sum to be capped?
You can ask. Some contractors will agree a ceiling or agree to stop and consult you at a set figure. Whatever you agree, put it in writing.
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