How is the gross valuation for a JCT interim payment built up?
Work properly executed, materials on site and listed off-site items, plus the other amounts the contract adds, less retention and the total already certified.
Updated: 15 September 2026. By Jack Butler-Kettle, Quantity Surveyor & Claims Consultant.
The answer
The gross valuation is the cumulative value of everything the contract says is payable at the Interim Valuation Date, and the sum due is that figure less retention and less the amounts already certified. Under the interim payment provisions in section 4 of SBC/Q 2016 the valuation is built in layers. The first is the value of work properly executed, measured against the Contract Bills at the Interim Valuation Date and including Variations valued under section 5 and any adjustment the contract makes for approximate quantities; work that is defective and not made good is not properly executed and comes out. The second is materials and goods delivered to the site for the Works, provided they are there reasonably and not prematurely and are adequately protected against weather and damage. The third is listed items held off site, where the Contract Particulars list them and the conditions the contract attaches to them have been met. To those are added the other amounts the contract puts through the Interim Certificate, including loss and expense that has been ascertained and fluctuations where they apply; some of these carry retention and some do not, and the contract says which. Retention at the Retention Percentage is then deducted from the parts that carry it, along with any deductions the contract allows against the Contractor, such as the cost of work the Employer has had others carry out after the Contractor failed to comply with an instruction. Finally the total stated as due in previous Interim Certificates is deducted and the balance is the sum due for the period. The usual failures are valuing to the application date rather than the Interim Valuation Date, carrying forward last month's measure without checking what was actually done, taking materials on site that are unprotected or were delivered early, and applying retention to loss and expense, which the contract does not.
Example
The situation
At the fourth Interim Valuation Date, work properly executed measures £820,000 including £35,000 of Variations, materials on site are £40,000 of which £8,000 is unfixed plasterboard delivered two months early and stored outside, and £22,000 of loss and expense is ascertained to date.
What happens
- The plasterboard comes out, leaving materials of £32,000.
- Retention at three per cent applies to the £852,000 of work and materials, giving £25,560, and not to the loss and expense.
- The gross valuation is £874,000 and retention brings it to £848,440.
- The £720,000 stated as due in the first three certificates is deducted.
The valuation in figures
| Item | Amount |
|---|---|
| Work properly executed, including £35,000 of Variations | £820,000 |
| Materials on site after the plasterboard comes out | £32,000 |
| Loss and expense ascertained | £22,000 |
| Gross valuation | £874,000 |
| Less retention at three per cent, £25,560 | £848,440 |
| Less £720,000 previously certified, sum due | £128,440 |
The outcome
The Interim Certificate states £128,440 as the sum due, with the £8,000 of plasterboard excluded and retention held only on work and materials.
Left in, the plasterboard would have put £8,000 in the certificate for material the Employer could refuse at the next valuation once the damage showed.