Mullen and Mullen (Child support)

This matter concerned an appeal by the father, Mr. Mullen, against a child support administrative assessment made by the Registrar of the Child Support Agency. The dispute centred on the father's income for the purposes of calculating his child support liability, specifically whether the Registrar had correctly estimated his income based on available information. The appeal was heard by the Federal Magistrates Court of Australia.

The primary legal issue before the Court was whether the Registrar had erred in estimating the father's income for the relevant child support period. This involved determining whether the Registrar had sufficient grounds to depart from the income declared by the father and whether the estimation method employed was reasonable and in accordance with the *Child Support (Registration and Collection) Act 1988* (Cth). The Court also considered the adequacy of the information available to the Registrar at the time the assessment was made.

The Court found that the Registrar had not been provided with sufficient information to make a reliable assessment of the father's income and had therefore acted on insufficient grounds in estimating it. The Court noted that the father had provided some income details, and while these may have been incomplete, the Registrar had not adequately explored alternative avenues for verification or sought further clarification before proceeding with an estimation. Consequently, the Court determined that the administrative assessment was not soundly based. The Court set aside the Registrar's decision and substituted its own assessment, taking into account the available evidence and applying the principles of the *Child Support (Registration and Collection) Act 1988*.