If one parent is starting or returning to work, while the other parent remains on parental leave until a later date, you will only be eligible to apply once both parents have either returned to work or have a start or return to work date within one month of the start of term (that is, 30 September, 31 January or 30 April).
If you are on paid annual leave and receiving your salary as normal, this counts as having returned to work for the purposes of eligibility for the working parent entitlement.