The London congestion charge is a fee charged on most motor vehicles operating within the Congestion Charge Zone (CCZ)[1] in Central London between 07:00 and 18:00 Mondays to Fridays. Saturday and Sunday 12:00 noon to 6pm. It was introduced on 17 February 2003 and remains as one of the largest congestion charge zones in the world despite the cancellation of the Western Extension which operated between February 2007 and January 2011. The charge aims to reduce high traffic flow in the central area and raise investment funds for London's transport system.
More information on the Wikipedia page [1], and the TfL page is [2].