There are transitional arrangements for some agreements entered into before 1 March 2000. Also the parties' combined market share may grow beyond the 25 per cent limit. For these reasons businesses may prefer to notify agreements to the Office of Fair Trading and obtain individual exemption. The new prohibition came into force on 1 March 2000. It applies if the abuse affects trade within the United Kingdom or any part of it.
Dominance is an economic concept which is difficult to define.
However, it can be presumed if an undertaking has a market share persistently over 50 per cent, and will be unlikely if its market share is less than 40 per cent. They prohibit anti-competitive agreements, and abuse of a dominant position. The UK Competition Act reproduces those provisions. Chapter I of the Act prohibits anti-competitive agreements, and Chapter II prohibits abuse of a dominant position. There are small variations in the implementation of the two regimes, but they are based on identical principles.