Hi, tl92. I am thinking he knew he would likely be fussed at if he admitted he didn't mow, and he was trying to put it off. Surely he knew you would notice at some point.

I suggest you tell him what you told us. Maybe say something like, "Son, I feel betrayed and frustrated because you didn't tell me the truth about the yard. First of all, I am wondering why you didn't mow it after I asked you to, and second, I am wondering why you told me you did mow it when you didn't."

Then see what he says. Perhaps a talk about his now being an adult and having adult responsiblities, and needing to pitch in as part of the family team. After all, he is getting room and board for free. And everybody needing to treat each other as adults. But lying is more of a young person's behavior.....