If you drive more miles than agreed in your contract, you will have to pay an excess mileage charge.
The charge varies but depends on things such as: which vehicle you are leasing, and whether you have taken out a maintenance package. It can range from 2p upwards for each mile you've travelled over your contract.
Before you enter into a leasing contract, your Account Manager will help you figure out how many miles you will travel over a year. This will help you to avoid going over your limit and reduce the possibility for an unexpected charge at the end of your contract.
The charge per excess mile will be stated in your quote and leasing contract, so you will be aware of the cost before taking delivery of a vehicle.