How do I claim variations after the job is finished?

Start with the deadlines. Every Australian state and territory has security of payment law, and each sets its own time limit for a payment claim, so check the law for your site. For example, under Queensland's BIF Act 2017 a claim must usually be made within 6 months of the work, or within the contract time if that is shorter. Check the contract notice rules too.

Gather the contract, drawings, programme, emails, diaries and cost records. Build a timeline of what changed and when.

Price each change from timesheets, invoices and subcontractor accounts. Be open about which costs are proven and which are estimated.

Send one claim with a register of changes and an index of proof. If it is refused, the same file supports adjudication.