If you are making gifts of cash or personal possessions, you will be asked if any of the intended recipients is under 18.
This is because a child cannot usually give a valid receipt for a gift under a will. And children under 18 cannot own real property (i.e. land).
If any of the beneficiaries is under 18, you can specify that their parent or guardian is authorised to give a receipt on their behalf, or that they can do so themselves if they have reached 16. The will then contains a clause which specifies the choice you’ve made.
Once such a beneficiary has reached 18, the need for a receipt on their behalf obviously disappears.
For more information see our page Providing for your children in a will.