There isn't a clear-cut answer to how long you have to take back a new car. If your contract allows for a cooling-off period, it should state exactly how long that lasts — a few days to a week is common. However, if you're filing a lemon law claim, you will need to return the vehicle to the dealer to allow them an opportunity to fix it. Each state has guidelines about how long you have to file a claim after purchasing a car that you deem to be a lemon. This can stretch anywhere from a few months to a few years, depending on where you live.