As the registered owner of the car is the lease provider, they will hold the V5C, also known as a vehicle log book. To receive a copy, you can request this directly from your them. Check out this article for a list of lease provider contact details: What are the contact details for my car provider?
Your V5C, also known as a car log book, can be used as proof that your company is leasing the vehicle from the lessor and that you have permission to drive it. It contains the information you need to be able to apply for a parking permit or register for a congestion charge.
