Your 8 year old now understands about actions and consequences. For instance, he knows if homework is not done, there will be trouble later. In order to escape trouble, children at this age can get into lying.
What you need to know
It’s very important to give the assurance to your child that no matter what has happened, you will help him through, but he has to speak the truth.
Your child is no more a child; at the same time he lacks maturity of an adult. At this critical stage, it becomes very important to tell him the consequences of lying. Tell him what’s wrong with lying. It breaks down the trust and both of you have to trust each other. Once he understands this and finds you calm when he comes to you with the truth, he will replace fear and anxiety with open communication and trust.
What you can do
Help your child solve problems. If he has lost a book, help him trace it. He is growing up; let him explore his ability to find solutions to problems rather than resorting to lying. Above all as a family, lay down some rules like “No lying allowed in the house by any family member"."We tell the truth even when it is hard to do".
By being calm, building trust and modeling the right behaviour, you are teaching your child the value of speaking the truth always, which develops his moral and emotional strength.