Issue one pricing brief.
Start with a dated drawing register, a written scope and a finishes schedule. Tell each tenderer which documents to price and which earlier revisions have been superseded. If you only have a concept, ask for a budget estimate with assumptions stated so everyone understands how it may change.
Identify the site, intended use, delivery timing and constraints. For a tenancy, include landlord information and access rules. For a home, include the survey and available site investigations. A site visit can uncover issues that are invisible in the drawings.
Ask for the same breakdown.
Ask each builder to separate work included in the price, items allowed for at an estimated cost and work excluded. Check who is responsible for approvals coordination, consultant design, disposal, protection, temporary services and final testing. Confirm whether the price includes GST.
For example, two quotes can include joinery at very different levels of detail. Compare the number of units, hardware, finish, installation and coordination with electrical or plumbing work before comparing the price.
Write down the assumptions that could change the price.
Record selections still to be made, conditions that can only be checked after opening up and supplier lead times. Assign an owner and a decision date to each item. Where a hidden condition cannot be priced firmly, agree how it will be investigated and assessed.
Before accepting a price, compare the scope line by line and check the dates and documents referenced in the contract. This gives you a reliable baseline when you need to discuss a change.