In order for children to fully understand finances and how money “works,” they have to learn about debt. The age of your child will determine how you define debt so they can understand.
Make sure you use terms and examples that they are already familiar with.
You can begin with the concept of borrowing something such as a toy from a friend. Explain the need to return the toy to its owner. And if the toy can’t be returned in its original condition then it needs to be replaced by a similar item of equal value. Your child should be able to understand that until that item is replaced, paid for, he is in debt to the person who owned the item.
For the “tween” set you can use real money items and examples. Set up a scenario where your child wants something, a new bicycle, for instance. Write down and discuss the amount of money the bike costs, the amount of money your child has, the amount of money he earns through allowance, or anticipates receiving for a gift, etc.
Talk about whether or not he can “afford” the bike right now, and if he can pay it off within a reasonable amount of time. This discussion will include installment payments where instead of paying back the “loan” with all of their allowance each week, they pay smaller amounts so as to keep some money for their usual “living expenses.” It’s important to work financial terms into the conversation as soon as you child is able to understand them.
Then, actually carry out a transaction. Keep it written down; sign a contract, have them make payments and even set up an amortization schedule so they can see how interest works. Going through this process will give your child an excellent opportunity to learn about personal finances.