Typical gratuity is 15-20% of your total bill.
Most limousine companies charge the 15-20% gratuity automatically upfront when you pay for your reservation. However, in most cases the driver does not get this whole portion; each limousine company has a different policy, for example: some companies may split the gratuity between all drivers and the administrative staff.
In this case, you can give him/her an addition 10% or so.
If the limousine company doesnít charge the gratuity upfront, youíre expected to give at least 20% cash tip for the driver. (preferably in cash)
Itís a good idea to give the driver half of the tip in the beginning or during the service and the rest at the end. This way the driver would have a chance to show you his/her appreciation and provide you an excellent service