Practical Completion

Practical completion is a formal milestone in construction contracts that marks the point at which works are substantially complete and the client can take possession of the building or site - even if minor defects remain outstanding. The term is used in JCT, NEC, and most standard-form construction contracts, with "substantial completion" used as the equivalent concept in US practice. In most contracts, practical completion triggers a chain of simultaneous consequences that directly affect how and when a contractor is paid.

What Practical Completion Triggers

The moment a contract administrator or architect certifies practical completion, several contractual events begin. The most significant for contractors is retention release: typically 50% of the total retention withheld during the project is released at practical completion, with the remaining 50% held until the end of the defects liability period.

Alongside retention, practical completion starts the defects liability period (DLP) - the contractual window, usually between 6 and 24 months, during which the contractor has the right to return and remedy defects before the final retention is released. Liquidated and ascertained damages (LADs) - the daily or weekly financial penalty for late completion - stop accruing from the date of practical completion. Insurance responsibility for the works typically transfers from the contractor to the client on the same date.

For invoicing purposes, practical completion is also the point at which most contracts allow the contractor to submit the final account - the document setting out all contract sums, agreed variations, and outstanding adjustments before the final payment is calculated.

Practical Completion vs. Final Completion

Practical completion and final completion are distinct milestones separated by the entire DLP. At practical completion, works are substantially done but minor defects are expected and acceptable. The client takes occupation, but the contractor retains responsibility for correcting any defects notified during the DLP.

Final completion - sometimes called making good of defects or final account settlement - marks the end of the DLP. Once the contract administrator confirms all notified defects have been rectified, the remaining retention is released and the final account closes. In practice, the gap between practical completion and final completion is often six to twelve months on commercial projects, and up to two years on larger schemes.

Contractors who do not actively track both dates face two consequences: missing the final retention invoice trigger entirely, or failing to respond to defect notices within the DLP and losing the right to remedy defects rather than face a deduction from the final retention. Zigaflow's job and project tracking tools allow contractors to log both milestone dates at contract stage and set reminders ahead of each retention release point.