COVID-19 has had a significant impact on the mental health and wellbeing of the Australian population. This paper provides detailed data on the mental health of those aged 18 years and under, as reported by an adult in their household. For children aged 2 to 4 years, parents and carers do not report a dramatic worsening in mental health outcomes. For those aged 5 to 18 years, however, it would appear that parents/carers think that COVID-19 has had a large negative impact on mental health. The mental health of adolescents and young adults aged 15 to 18 is of particular concern, with 71.0 per cent of adolescents and young adults in this age group reported to have had a worsening in mental health outcomes due to COVID-19, significantly higher than any other age group. A comparison of our results with those from a survey undertaken in July 2020 suggests that these negative mental health impacts have gotten worse. Outcomes appear to have worsened particularly for children who live in one of the states that have had long lockdown periods and where the parent/carer has high levels of psychological distress themselves. There is also some evidence of a greater worsening in mental health for those children whose parent/carer is Aboriginal and/or Torres Strait Islander,. The other main finding from the analysis is that there were significant barriers in finding mental health support. Around two-in-five carers reported that it was difficult or very difficult (39.9 per cent), with 12.2 per cent reporting that it was very difficult.