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GST on Variations and Retentions in Australian Construction
By Rami Rajkumar, CPA · Founder & Partner, TechEdge Accounting · Updated 18 June 2026 TL;DR. Variations and retentions are the two most-mishandled GST events in AU construction. Variations are taxable supplies at the point of agreement (not on completion). Retentions follow the original supply's GST treatment — releasing a retention is not a new taxable supply. Tax invoice timing for variations matters: GST is payable when the variation is invoiced or when payment is received
May 278 min read
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