Aiboni and Howald (Child support)

This matter concerned an appeal by the father against a decision of the Child Support Registrar who disallowed his objection to a child support assessment. The dispute arose from the use of the mother's provisional income for two years of child support calculations, which were later updated following the submission of her tax returns. This correction led to the cessation of the assessment and the identification of the case for service recovery work. The father contended that a system error had resulted in the incorrect use of provisional income, impacting the assessment.

The primary legal issue before the Member was whether the Registrar was obliged to amend the child support assessment to correct the error arising from the use of provisional income, notwithstanding that the father had no knowledge of the mother's actual incomes during the relevant period and the mother had not objected to the assessment. The Member was required to consider the provisions of the *Child Support (Registration and Collection) Act 1988* (Cth) and the *Child Support Assessment Act 1989* (Cth) in determining the Registrar's discretion and obligations in such circumstances.

The Member reasoned that while a system error had occurred, the Registrar retained a discretion regarding the amendment of assessments. The father's argument that he bore a significantly greater proportion of the child's costs and that the amount of the error was insignificant were factors considered. However, the Member found that the Registrar was not *obliged* to amend the assessment to correct the error, particularly as the mother had not objected and the father had not demonstrated that the error caused him prejudice beyond the general operation of the assessment. The Member concluded that the Registrar's decision to disallow the objection was not unreasonable in the circumstances.

The decision of the Registrar was set aside and substituted with a finding that the objection was disallowed.