The ATO has published an interim Decision Impact Statement in relation to the decision of the Full Court of the Federal Court in Chemical Trustee Limited v FCT  FCAFC 27. The taxpayer's application for special leave to appeal from the Full Court's decision was refused by the High Court on 15 August 2014 - see  HCATrans 169.
The case concerns whether the Commissioner, having obtained judgment for an income tax debt, is prohibited from obtaining judgment for an income tax debt arising out of an amended assessment for the same income year. The Full Court held that the cause of action arising from an amended assessment of income tax is a separate cause of action from that arising from an earlier assessment for the same year of income. Consequently, the doctrine of res judicata does not prevent the Commissioner from recovering on an amended assessment if he already has judgment for the original assessment. The High Court in refusing special leave confirmed the correctness of the Full Court's decision.
The Commissioner states that he agrees with the decision. He states that if he obtains judgment for an income tax debt and that judgment is not set aside, he will not sue again on the same notice of assessment. However, if the assessment is amended and the amendment gives rise to additional tax, the Commissioner may sue to recover the additional tax.