Recording how much money they receive (income), how much they spend (outgoings) and how much is left (balance) is a good first step to helping your young person keep track of their money. They might find it helpful to write this down in a notebook or spreadsheet.
Additionally, encourage them to write down details of any subscriptions, paid-for apps and direct debits. Nobody wants to be paying for something they don't use!
The related links on this page provide more detailed support to help you support your young person keep track of their money and move towards greater financial independence.