The Home Building Contracts Act governs the progress payment system, which is designed to protect all parties. This includes owner, Builder and tradespeople. The Act entitles an owner to inspect work, or have an independent inspector inspect on their behalf to ensure that a stage of work has been completed proficiently.
Payment should not be made if works are incomplete. Although you may find you are in breach of the Home Building Contracts Act if you withhold payment unreasonably.
The WA Building Commission provide useful information on building contracts and progress payments and should be consulted if you’re unsure of whether you should make a payment to your Builder.