1. Your friend has a new job. Perhaps she has started it. You ask her: Have you started your new job yet?
2. Your friend has some new neighbours. Perhaps he has met them. You ask him: Have you met them yet?
3. Your friend has to pay her electricity bill. Perhaps she has paid it. You ask her: Have you paid your electricity bill yet?
4. Tom was trying to sell his car. Perhaps he has sold it. You ask a friend about Tom: Has Tom sold his car yet?