Answered by Shaykh Faraz Rabbani
I have a Trust Fund set up for my child, with myself acting as the Trustee untill she reaches the age of 18 (My name is in the account documentation). Do I need to pay Zakat on the money which I have saved for her? I look forward to hearing from you.

Walaikum assalam wa rahmatullah,
I pray that this finds you well, and in the best of health and spirits. May Allah grant you all good and success in this life and the next.
If ownership of those funds has been transferred to the child (with all that this entails, including those funds no longer being possible to return to the parent until the child becomes a discerning adult and willingly accepts) then no zakat is due on such funds until the child reaches puberty.
Once a child reaches puberty they are Islamically considered an adult, and are responsible to pay zakat. Their guardian is responsible to pay zakat on the money they keep in trust for them from this point.
See:
Signs of Puberty – answered by Sidi Sohail Hanif
[ref: Ibn Abidin, Radd al-Muhtar]
And Allah alone gives success.
Faraz Rabbani