Auto Trader has floated on the London Stock Exchange, pricing its shares at 235p. This values the business at £2.35 billion.
Conditional share dealings began at 8am, and unconditional dealing starts on Tuesday.
The offer comprises 590 million shares, representing 59% of Auto Trader's issued share capital on admission.
According to today's statement to the London stock exchange, Apax, the private equity owners of Auto Trader, will raise £926.2m through the IPO.
The flotation will raise around £437m net for Auto Trader to pay down some of its debt facilities.
In its prospectus, Auto Trader said its directors believe that the offer and admission will "position Auto Trader for the next stage of its development, by further raising the profile of the group and providing an appropriate capital structure for future growth".
On admission, the company has available to it, in aggregate, £1,026.0 million of available funds, comprising of net proceeds from the offer of £437.0 million, £540.6 million of term debt under its new facilities, and £48.4 million from its existing available cash.
The shares jumped to 266.5p in early trading, hitting a value of £2.6bn, before closing the first day's trading at 256p.
Auto Trader is expected to drive into the FTSE 250 the next time the index is reconstituted.
Auto Trader is now predominantly focused on the UK and Ireland after recently selling its businesses in Italy, the Netherlands and South Africa.