In Australia, changing a child’s surname is considered a major long-term decision under the Family Law Act 1975. This means both parents who share parental responsibility must agree to the change.

If both parents agree, the process is relatively straightforward:

• You can apply through your state’s Registry of Births, Deaths and Marriages (e.g. in Queensland, through the Queensland Registry).
• You'll need to complete the relevant forms and provide evidence of consent from both parents.

If the other parent does not consent, you cannot unilaterally change your child’s name. In this case, you’ll need to:

1. Apply to the Family Court or Federal Circuit and Family Court of Australia, asking for an order to allow the change.
2. Provide a strong justification as to why the change is in the best interests of the child.

The court will consider several factors, including:

• The child’s relationship with each parent
• The impact of the name change on the child’s identity
• The age and views of the child (especially if they are mature enough to express a preference)
• Any potential confusion caused by having a different surname to one parent
• The reason for the name change (e.g., safety concerns, domestic violence, or practical issues at school)
• Depending on the child age and maturity, the child's views may be taken into consideration

You can apply to change your child’s surname after separation, but if both parents don’t agree, you’ll need to go through the court. The key consideration for the court is always the best interests of the child, not the wishes of the parents. If you’re thinking about changing your child’s name, it’s wise to speak with a family lawyer to understand your rights and options.