Milestone Payments for Large UK Construction Projects: JCT Contracts and Interim Valuations

For trade contractors taking on larger projects — extensions, full refurbishments, commercial fit-outs, or multi-phase installation contracts — managing cash flow over the duration of the project is one of the most critical challenges. A plumber who spends six weeks on a commercial project cannot wait until practical completion to invoice; the materials alone may represent a significant portion of monthly turnover. Milestone-based payment structures, underpinned by JCT contract provisions and the Construction Act 1996, are the standard mechanism for ensuring that contractors are paid progressively as work is completed.

What Milestone Payments Are and Why They Matter

A milestone payment is a partial payment made to a contractor upon the completion of a defined stage of work, rather than on a time-based or final completion basis. Milestones are typically tied to observable events in the construction programme: completion of groundworks, completion of the structural shell, first fix electrical and plumbing, plastering, second fix, and practical completion are common milestone stages on a domestic extension or renovation. On commercial projects, milestones may be defined by reference to programme dates, percentage of overall works completed, or specific deliverables such as commissioning of plant and equipment. Milestone payments reduce the contractor's working capital requirement by ensuring that income arrives before all work is complete, and they give the client a mechanism for checking that progress is on track before releasing each payment. The Construction Act 1996 underpins this by providing a statutory right to stage payments for any project lasting more than forty-five days.

JCT Contracts and Interim Valuations

The Joint Contracts Tribunal produces a range of standard form contracts that are widely used in the UK construction industry. For large residential projects, the JCT Homeowner contracts or JCT Minor Works contracts are commonly used. For commercial work, JCT Intermediate and JCT Standard Building Contracts provide a more detailed framework. In JCT contracts, the standard mechanism for progressive payment is the interim valuation: the contractor submits a valuation of the work properly executed to date, including any materials on site, and the contract administrator — typically an architect or quantity surveyor — certifies the amount due within a specified period. The certified amount is then payable by the employer within a further period, commonly fourteen days from the certificate date. If the contract administrator under-certifies the work, the contractor can challenge the valuation through the adjudication process.

Setting Up Milestone Stages and Payment Applications

For contractors who are not working under a formal JCT contract — for example, on smaller domestic jobs with a bespoke agreement — defining clear milestones in the contract documentation at the outset is essential. Each milestone should describe the work to be completed, the percentage of the contract sum released on completion of that milestone, and the basis on which the milestone will be determined as achieved. Ambiguously defined milestones are a common source of dispute: if a milestone is described as "first fix complete" without specifying which trades are included, a client can refuse to certify the milestone as achieved because the first fix plumbing is done but the first fix electrical is not. Detailed milestone definitions in the contract protect both parties by making clear what is expected before each payment is due.

Retention: How It Works and When It Is Released

Retention is a mechanism in JCT and other standard form contracts whereby the employer withholds a percentage — typically 3 per cent to 5 per cent — of each interim payment, holding it as security against the contractor's obligations to complete the work and remedy any defects. Retention is usually divided into two halves: half is released at practical completion of the works, and the remaining half is released at the end of the defects liability period — typically six or twelve months after practical completion — provided that any notified defects have been made good. Retention can represent a significant sum on large projects: on a £200,000 contract with 5 per cent retention, the contractor may be owed £10,000 in retained funds that will not be released until the defects liability period expires. The Construction Act requires that retention funds be protected, and there have been longstanding industry discussions — not yet resolved in legislation — about mandatory trust funds for retention monies to prevent main contractors from using subcontractors' retention as working capital.

Practical Completion and the Defects Liability Period

Practical completion is the point at which the works are sufficiently complete for the employer to take possession of and use the building, even if minor snagging items remain. In JCT contracts, practical completion is certified by the contract administrator and triggers several important events: the release of the first half of retention, the commencement of the defects liability period, the transfer of insurance responsibility for the completed works to the employer, and the start of the final account assessment period. After practical completion, the employer notifies the contractor of any defects that appear during the defects liability period. The contractor is obliged to make good those defects at no extra cost, and only once they are made good to the contract administrator's satisfaction is the final certificate issued and the remaining retention released. Contractors should retain all site records, inspection reports, and completion sign-offs as evidence of the standard of work delivered at practical completion.

Variation Orders and Final Account

Construction projects rarely proceed exactly as initially specified. Changes to the scope of work — whether client-initiated variations, design changes, or unforeseen site conditions — must be managed through a formal variation order process to ensure that the contractor is paid for additional work and the client knows what additional costs are being incurred. Each variation order should describe the change, identify the contract clause under which it is being issued, and state the additional or omitted sum. In JCT contracts, variations are valued by reference to the rates and prices in the bill of quantities or schedule of works where applicable, or by reasonable rates where no applicable rates exist. The final account is the final reconciliation of all sums due under the contract, incorporating the original contract sum adjusted for all variations, any claims for loss and expense, and any other adjustments, less the amounts already paid. The final account should be agreed and the final certificate issued within the timeframe specified in the contract.

How QuotCraft Manages Milestone-Based Projects

QuotCraft's project management tools support milestone-based payment structures from the initial quotation through to final payment. When setting up a project, you define the payment stages with their descriptions, trigger conditions, and percentage of the contract sum. QuotCraft then automates the issuance of payment applications at each stage: when you mark a milestone as complete, the platform generates the appropriate payment application or invoice and sends it to the client, with a reminder system that follows up if payment is not received within the specified period. Retention tracking is built into the milestone structure, so QuotCraft automatically calculates the net sum due after retention at each stage and tracks the total retention outstanding. When the defects liability period expires and the retention becomes due for release, QuotCraft flags this for action and generates the retention release invoice. The complete payment history and document trail is stored in the project record, providing the contemporaneous evidence that any construction dispute — whether through adjudication or in court — will require.