Back-charge
A back-charge is a cost the builder claims against you - rectification by others, cleaning, plant hire, supervision - typically deducted from your next payment under the contract's set-off clause.
Legitimate back-charges exist. The problems are procedural: charges raised without notice, without substantiation, long after the event, or at rates you never agreed. The contract's set-off and notice drafting decides whether you find out before or after the money is gone.
Why it matters to subbies
Respond to every back-charge in writing, promptly, even when small - silence reads as acceptance, and patterns set on small charges scale to big ones. If the deduction leaves a payment claim underpaid, security of payment machinery may apply to the gap.
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General information for Australian subcontractors, not legal advice - contract drafting and state legislation vary and change; your document and your state's Act govern. Written by Mat Kennedy at The Construction Contracts Co.