DEPUTY COMMISSIONER OF TAXATION -v- SADLEIR [2026] WASC 73 | Case summary

On the basis of the evidence adduced by the plaintiff, I am satisfied the plaintiff has made out a prima facie case.
Mr Mitchell verifies in the First Mitchell Affidavit that, as at 29 October 2025, at about the time the Application was made, the total amount due and payable by the defendant to the Commonwealth of Australia in relation to the unpaid income tax for the Income Tax Periods and GIC less payments and/or credits, was $2,886,620.67.[24]
Attached to the First Mitchell Affidavit is a certificate signed by Julian Nicholas Roberts, a Deputy Commissioner of Taxation, made pursuant to s 350‑10(3) in sch 1 to the TAA, which certifies the defendant's tax-related liabilities and that, as at 29 October 2025, the amount of $2,886,620.76 was due and payable by the defendant in respect of his liability for unpaid assessed income tax and GIC.[25]
Mr Mitchell verifies in the Second Mitchell Affidavit that, as at 9 March 2026, the total amount payable by the defendant to the Commonwealth of Australia in relation to the unpaid income tax for the Income Tax Periods and GIC, less payments and/or credits, was $2,998,865.67.[26]
Attached to the Second Mitchell Affidavit is a further evidentiary certificate dated 9 March 2026 signed by Julian Nicholas Roberts, a Deputy Commissioner of Taxation, pursuant to s 350‑10(3) in sch 1 to the TAA, which certifies the defendant's tax-related liabilities and that the amount payable by the defendant in respect of the unpaid assessed income tax and GIC was $2,998,865.67.[27]
I accept the plaintiff's submission to the effect that the operation of the conclusive evidence provisions outlined, and the evidentiary certificates adduced is that the defendant is liable to pay the amounts of assessed income tax and GIC claimed. As submitted by the plaintiff, the effect of the conclusive evidence provisions in s 350-10 of sch 1 to the TAA is that the defendant does not have any legal or factual basis to resist judgment. Nor has he sought to raise any.
As stated by the majority of the High Court in Broadbeach, 'harsh though the operation of these provisions may be, they implement a long‑standing legislative policy to protect the interests of the revenue.'[28]

DEPUTY COMMISSIONER OF TAXATION -v- SADLEIR [2026] WASC 73 | Case summary | Zoe

On the basis of the evidence adduced by the plaintiff, I am satisfied the plaintiff has made out a prima facie case.
Mr Mitchell verifies in the First Mitchell Affidavit that, as at 29 October 2025, at about the time the Application was made, the total amount due and payable by the defendant to the Commonwealth of Australia in relation to the unpaid income tax for the Income Tax Periods and GIC less payments and/or credits, was $2,886,620.67.[24]
Attached to the First Mitchell Affidavit is a certificate signed by Julian Nicholas Roberts, a Deputy Commissioner of Taxation, made pursuant to s 350‑10(3) in sch 1 to the TAA, which certifies the defendant's tax-related liabilities and that, as at 29 October 2025, the amount of $2,886,620.76 was due and payable by the defendant in respect of his liability for unpaid assessed income tax and GIC.[25]
Mr Mitchell verifies in the Second Mitchell Affidavit that, as at 9 March 2026, the total amount payable by the defendant to the Commonwealth of Australia in relation to the unpaid income tax for the Income Tax Periods and GIC, less payments and/or credits, was $2,998,865.67.[26]
Attached to the Second Mitchell Affidavit is a further evidentiary certificate dated 9 March 2026 signed by Julian Nicholas Roberts, a Deputy Commissioner of Taxation, pursuant to s 350‑10(3) in sch 1 to the TAA, which certifies the defendant's tax-related liabilities and that the amount payable by the defendant in respect of the unpaid assessed income tax and GIC was $2,998,865.67.[27]
I accept the plaintiff's submission to the effect that the operation of the conclusive evidence provisions outlined, and the evidentiary certificates adduced is that the defendant is liable to pay the amounts of assessed income tax and GIC claimed. As submitted by the plaintiff, the effect of the conclusive evidence provisions in s 350-10 of sch 1 to the TAA is that the defendant does not have any legal or factual basis to resist judgment. Nor has he sought to raise any.
As stated by the majority of the High Court in Broadbeach, 'harsh though the operation of these provisions may be, they implement a long‑standing legislative policy to protect the interests of the revenue.'[28]

DEPUTY COMMISSIONER OF TAXATION -v- SADLEIR [2026] WASC 73 (12 March 2026)

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Cases Cited (13)