The first lies are a developmental milestone, awkwardly
Around four, most children begin to tell deliberate untruths. Parents find this alarming. Developmentally it is the opposite of alarming.
Lying requires knowing that another person holds beliefs that differ from yours and can be influenced. That understanding arrives in the same window, and the first lies are its clumsy first application — usually transparent, frequently about chocolate, and delivered while standing in the evidence.
Which does not make it fine
The milestone explains the behaviour; it does not license it. But it changes what a useful response looks like. Interrogation of a four-year-old about a lie generally produces more lies, because the skill is new and they are practising.
Make the truth cheap. A child who expects the roof to fall in has an obvious reason to try the alternative.
Stating what you saw rather than asking a question the child will be tempted to answer falsely avoids the whole contest: "the chocolate's gone and I can see it on your face — let's clean up" ends it without a test.