Interim Valuations and Application for Payments
Introduction
Interim valuations are the engine of construction cash flow. On any project lasting more than a few weeks, the contractor cannot be expected to finance the entire works until completion — interim payments allow regular compensation for work done, keeping the supply chain solvent and the project moving. For the quantity surveyor, preparing and certifying interim valuations is one of the most routine yet consequential tasks in practice. Get it right and the project runs smoothly. Get it wrong — over-value, miss a notice deadline, or certify without proper records — and you are looking at disputes, adjudication, and professional liability.
This article explains how interim valuations work under UK law and the two most common contract forms, walks through the gross valuation method, and flags the mistakes that catch out even experienced practitioners.
The Legal Framework
The Housing Grants, Construction and Regeneration Act 1996 (commonly called the Construction Act), as amended by the Local Democracy, Economic Development and Construction Act 2009, establishes the statutory basis for payment in construction. Any construction contract exceeding 45 days must include an adequate mechanism for interim and final payments. The Act prescribes a strict notice regime that the QS must understand thoroughly.
The paying party must serve a payment notice no later than five days after the payment due date, specifying the sum considered due and the basis of calculation (s.110A). If the employer intends to pay less than the notified sum, a separate pay less notice must be served no later than seven days before the final date for payment (s.111). Failure to serve a valid pay less notice means the employer must pay the full notified sum — no exceptions. The contractor also has the right to suspend performance if payment remains outstanding after the final date, provided seven days’ written notice is given (s.112). Suspension carries entitlement to both additional time and reasonable costs of remobilisation.
How Interim Valuations Work Under JCT
Under JCT SBC 2024 (Standard Building Contract with Quantities), interim valuation dates are specified in the contract particulars — typically monthly. The contractor submits a payment application to the quantity surveyor stating the sum it considers due and the basis of calculation. The QS then measures and values the work, and the architect or contract administrator issues an interim certificate within five days of the due date. The due date is typically seven days after the valuation date, and the final date for payment is 14 days after that.
Under JCT DB 2024 (Design and Build), the process is similar but the contractor applies directly to the employer, who is responsible for issuing the payment notice. There is no independent certifier — the employer must manage the notice regime directly or appoint an employer’s agent to do so.
Under both forms, the QS’s role is critical: they prepare the valuation that forms the basis of the certificate, and any error in that valuation flows directly into the payment.
How Interim Valuations Work Under NEC4
The NEC4 Engineering and Construction Contract takes a different approach. The Project Manager assesses the amount due at each assessment date (Clauses 50–53), certifying payment within one week. The standard payment cycle runs 21 days from assessment date to final date for payment.
The amount due is the Price for Work Done to Date (PWDD) plus other amounts, less retention. How PWDD is calculated depends on the main option selected. Under Option A (activity schedule), PWDD is the total of prices for completed activities — binary, either done or not. Under Option B (bill of quantities), PWDD is measured quantity multiplied by the applicable rate. Under Options C, D, and E (target and cost-reimbursable), PWDD is Defined Cost plus Fee — the actual costs incurred by the contractor plus an agreed percentage mark-up.
The Gross Valuation Method
Regardless of contract form, the QS builds up each interim valuation using a consistent methodology. The gross valuation comprises:
Measured work to date — the value of work physically completed, measured against the bills of quantities or schedule of rates. Preliminaries — site establishment, management, temporary works, and insurances, typically valued pro rata based on programme progress. Materials on site — items delivered and stored on site, eligible for payment provided the contract permits it and ownership is verified. Materials off site — items manufactured but not yet delivered, subject to stricter conditions including proof of title, surety bonds, and insurance. Variations — valued at contract rates where available, or by agreement. Loss and expense — compensation for disruption or delay where the contractor has a contractual entitlement. Fluctuations — inflation adjustments where the contract provides for them.
From the gross valuation, the QS deducts retention (typically 5%, capped at 3% once a stated threshold is reached) and previous payments to arrive at the net amount due.
Worked Example: Interim Valuation No. 3
Consider a 12-month project with a contract sum of £1,500,000. At the end of month three, the QS prepares the following valuation:
| Item | Amount |
|---|---|
| Measured work to date (30% complete) | £450,000 |
| Preliminaries (£120,000 contract allowance × 30%) | £36,000 |
| Materials on site | £42,500 |
| Materials off site (bonded) | £55,000 |
| Variations (approved) | £28,000 |
| Loss and expense (documented) | £12,500 |
| Gross valuation | £624,000 |
| Less retention (5%) | (£31,200) |
| Less previous payments | (£185,000) |
| Net amount due | £407,800 |
The employer must pay £407,800 by the final date for payment unless a valid pay less notice is served. Retention of £31,200 is held against this valuation — 50% released at practical completion, the remainder at the end of the defects liability period.
Retention: How It Works Within Valuations
Retention is a percentage of the gross valuation withheld as security against defects and incomplete work. Standard JCT retention is 5%, often capped at 3% once certified payments reach a stated proportion of the contract sum. Half the accumulated retention is released when the architect certifies practical completion; the remaining half is released when defects have been made good at the end of the defects liability period (typically 6–12 months after PC). The QS should maintain a running retention schedule showing cumulative retention held, amounts due for release at each milestone, and reconciliation with the contractor.
Payment Notices: The Strict Regime
The notice regime under the Construction Act is unforgiving. The employer’s payment notice must be served within five days of the due date. If it is not, the contractor can serve a default payment notice, and the employer becomes liable for the sum stated. If the employer wishes to pay less, the pay less notice must be served at least seven days before the final date for payment. A pay less notice served one day late is invalid — and the employer must pay the full notified sum.
Courts have reinforced this strictly. Pay less notices must clearly state the sum considered due and the basis of calculation; vague or incomplete notices will be struck down. The practical lesson for the QS is simple: diarise every deadline, serve notices early, and ensure every notice contains both the amount and the reasoning.
Common Mistakes
Over-valuation. Including work not yet completed or materials not verified on site. This effectively pre-funds the contractor and creates exposure if the project stalls or the contractor becomes insolvent. Always conduct a site visit before each valuation.
Front-loading. Certifying disproportionately high amounts early in the project — whether through inflated preliminaries, generous materials valuations, or aggressive percentage-complete assessments. Spread the valuation evenly and challenge high early applications.
Missing notice deadlines. A single missed deadline strips the employer of the right to withhold payment. Create a payment notice calendar at project start and circulate it to all parties.
Inadequate records. If the contractor disputes a valuation, the QS needs evidence: site photographs, measurement schedules, signed agreements on quantities, and copies of every notice served. Without a valuation file, the QS is exposed in adjudication.
Not checking materials ownership. Paying for materials on site without verifying that the contractor owns them. If the contractor has not paid the supplier, title may not have transferred — and the employer could lose both the money and the materials.
Practical Tips
Maintain a valuation file for every interim certificate — contractor’s application, QS calculation sheet, site visit notes, photographs, copies of all notices served, and the retention schedule. Keep these for at least six years.
Visit site 2–3 days before each valuation date. Walk the site with the contractor’s QS, agree the extent of completed work, verify materials, and discuss any queries. A collaborative site visit reduces disputes.
Agree measurement with the contractor before finalising. Share your draft valuation, reconcile differences, and obtain sign-off on the calculation basis. This does not mean accepting the contractor’s figures — it means ensuring both parties understand the valuation before it is certified.
Track variations separately. Maintain a variation register and include only approved variations in interim valuations. Provisional or disputed variations should be flagged, not certified.
APC Relevance
Interim valuations sit squarely within two RICS APC competencies: Quantification and Costing of Construction Works (measuring work, valuing progress, applying contract rates) and Contract Practice (understanding payment mechanisms, notice regimes, and the QS’s role in contract administration). APC candidates should be able to explain the gross valuation method, describe the statutory payment notice requirements, and discuss the differences between JCT and NEC4 payment mechanisms.
Further Reading on ProQS
For more on related QS skills, see these ProQS articles:
Contract Administration: JCT vs NEC — how the QS administers payments and certifications under each contract form.
Final Accounts and Settlement — how interim valuations feed into the final account process.
Construction Law for the Quantity Surveyor — the statutory framework governing payment obligations and dispute resolution.
Variation Valuation and Claims — how variations are valued and included within interim certificates.
Key References
Housing Grants, Construction and Regeneration Act 1996 — the primary legislation establishing statutory payment requirements for UK construction contracts.
Local Democracy, Economic Development and Construction Act 2009 — the amending Act that strengthened payment notice and pay less notice provisions.
RICS: Interim Valuations and Payment — professional guidance on best practice for QS interim valuation procedures.
Designing Buildings Wiki: Valuation of Interim Payments — comprehensive reference covering interim valuation principles and practice.
JCT Contracts — the Joint Contracts Tribunal, publisher of JCT SBC 2024 and JCT DB 2024 standard forms.