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Practical completion and defects liability calculator

From the date of practical completion, work out when the defects liability period ends, when each retention moiety is released, and when the final claim is due under your contract form.

1. Contract form

AS 4000 provides a final payment claim within 28 days after the last of the DLP expiry and the completion of defects rectification.

These are the periods the standard form commonly uses. The executed contract and its Annexure or schedules always govern. Every field below is editable.

2. Your project

Date of Practical Completion

The date certified, not the date claimed.

Defects liability period (months)

Commonly 12 months. Set in the contract particulars.

Final claim period (days after DLP)

Missing this can extinguish the final claim.

Contract sum (AUD)

Optional: turns retention into a dollar figure.

Retention held (%)

Commonly 5%, released in two moieties.

First moiety released

Day counting basis

Most standard forms count calendar days. Check yours.

Your dates

Practical Completion

Wed 30 Sep 2026

Entered. The defects liability period starts on this date.

First retention moiety released

Wed 30 Sep 2026  ·  $300,000

First moiety released at Practical Completion

Defects liability period expires

Thu 30 Sep 2027

Practical Completion plus 12 months.

Second retention moiety released

Thu 30 Sep 2027  ·  $300,000

On expiry of the defects liability period, subject to defects being rectified.

Final payment claim due

Thu 28 Oct 2027

Defects liability expiry plus 28 calendar days.

Retention: $600,000 held in total (5% of $12,000,000), released as two moieties of $300,000.

Defects liability is not a warranty

The defects liability period is a contractual mechanism that gives the contractor the right and the obligation to come back and fix defects, and gives the principal security while they do. It is not the limit of the contractor’s liability.

Statutory warranties and the general law run well past the DLP, commonly six years for breach of contract, and longer again for certain building defects under state legislation. A defect appearing in year three is not automatically the principal’s problem just because the DLP expired in year one.

Indicative dates based on the periods commonly used in standard contract forms. Your executed contract and its Annexure or schedules govern, and special conditions frequently change these periods. Confirm against the contract and take advice before relying on any of these dates.

What practical completion actually triggers

Practical completion is the pivot point of a construction contract. It is not the end of the job; it is the moment when a cluster of consequences all start at once.

Liquidated damages stop running. Risk and insurance responsibility usually pass to the principal. The defects liability period begins. The first retention moiety typically becomes releasable. The clock starts on the final claim. In most forms, possession of the site returns to the principal.

Because so much hangs on one date, disputes about whether practical completion has been reached are among the most common in construction, and the reason they matter is not the date itself, it is everything the date sets in motion.

The defects liability period is not a warranty

The defects liability period is a mechanism, not a limitation of liability. During the period, the contractor has both the right and the obligation to return and rectify defects, and the principal must allow it.

That right matters commercially. Rectifying your own defect costs your rate; having the principal engage someone else and charge you costs theirs. A contractor excluded from rectifying during the period usually ends up worse off.

The period ending does not end liability for defective work. It ends this particular process for dealing with it. Statutory warranties and general contractual liability run on their own timeframes, which are considerably longer.

Two moieties, and the second one is the long wait

Retention is conventionally released in two halves. The first is released at or shortly after practical completion. The second is released at the end of the defects liability period, once outstanding defects have been rectified.

Ordinarily that second release is six to twelve months after practical completion, depending on the contract. On a job where retention was first withheld two years earlier, the money has been out of the business a long time.

Diarise both release dates when practical completion is certified, not when you get around to it. Retention is very frequently released only when somebody asks, and the person who asks is the person who wrote the date down.

Contract forms count these periods differently

The standard Australian forms do not agree on how these periods run, and the differences are not cosmetic. Some run from the date of practical completion, others from the date of the certificate, and the two can be weeks apart.

Whether the period is counted in calendar days, business days or months also varies, and month-counting has its own trap at the end of a month. A period added to the 31st has to land somewhere in a shorter month, and the contract may or may not say where.

This calculator handles the month-end rollover explicitly and shows which day-counting basis it applied. Where the tool is uncertain about a particular form’s convention, it says so rather than guessing, because a confidently wrong final claim date is worse than an acknowledged gap.

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