There are two types of limo drivers: those paid an hourly rate or those paid a fixed rate, which is sometimes called fixed cost. Drivers paid hourly are paid for the time spent carrying a client around in their vehicle, usually several hours, but it depends on the job. Those who work on a fixed rate basis are paid a set amount for the duration of the job, with longer jobs paying more than shorter jobs.
When you rent a limo for the night, you're usually charged a set amount. The person driving the car is only paid for the time you're in the limo and not any time spent preparing the vehicle. For example, the driver may have to drive from home to the shop, pick up the car and drive to your home, but they're only paid from the moment you climb inside. They're not paid for any of the time they spend cleaning the vehicle either, or preparing it for future customers.
If you leave the car in disrepair or leave behind a mess, you should be prepared to leave a higher tip. You need to remember that the driver is responsible for cleaning the car, taking out any trash left behind and generally ensuring that it looks like new. This is all done on their own time, and not something that they're paid for. If you leave behind a mess, leave behind a higher tip, typically in the 25-35 percent range, depending on the size of the mess.
Generally speaking, you should base the tip on the length of the trip. Shorter trips require smaller tips, while larger trips necessitate a larger trip. For example if you're taking a short drive from the airport to your home, tipping $5-10 is acceptable. If on the other hand you're traveling an hour or longer, you should expect to tip at least $20. You can also leave behind a tip equivalent to 10% of the total bill, but that's on the low end of the spectrum.
Others believe that the size of the tip depends on the size of the car, especially if the car is rented by the hour. Limo drivers drive all types of cars from a Town Car up to the larger stretch limo. If you're renting a smaller vehicle by the hour, prepare to tip at least 10 percent of the total bill. For larger limos including the stretch model, leave behind at least 15 percent of the total bill as a tip for the driver.