4 (a) Except in relation to specifically exempted companies， such as those involved in charitable work， companies are required to indicate that they are operating on the basis of limited liability. Thus private companies are required to end their names， either with the word ‘limited’ or the abbreviation ‘ltd’， and public companies must end their names with the words ‘public limited company’ or the abbreviation ‘plc’。 Welsh companies may use the Welsh language equivalents (Companies Act (CA)2006 ss.58， 59 & 60)。

　　Companies Registry maintains a register of business names， and will refuse to register any company with a name that is the same as one already on that index (CA 2006 s.66)。

　　Certain categories of names are， subject to the decision of the Secretary of State， unacceptable per se， as follows：

　　(i) names which in the opinion of the Secretary of State constitute a criminal offence or are offensive (CA 2006 s.53)

　　(ii) names which are likely to give the impression that the company is connected with either government or local government authorities (s.54)。

　　(iii) names which include a word or expression specified under the Company and Business Names Regulations 1981 (s.26(2)(b))。 This category requires the express approval of the Secretary of State for the use of any of the names or expressions contained on the list， and relates to areas which raise a matter of public concern in relation to their use.

　　Under s.67 of the Companies Act 2006 the Secretary of State has power to require a company to alter its name under the following circumstances：

　　(i) where it is the same as a name already on the Registrar‘s index of company names.

　　(ii) where it is ‘too like’ a name that is on that index.

　　The name of a company can always be changed by a special resolution of the company so long as it continues to comply with the above requirements (s.77)。

　　(b) The action of passing off was developed to prevent one person from using any name which is likely to divert business their way by suggesting that the business is actually that of some other person or is connected in any way with that other business. It thus enables people to protect the goodwill they have built up in relation to their business activity. In Ewing v Buttercup Margarine Co Ltd (1917) the plaintiff successfully prevented the defendants from using a name that suggested a link with his existing dairy company. It cannot be used， however， if there is no likelihood of the public being confused， where for example the companies are conducting different businesses (Dunlop Pneumatic Tyre Co Ltd v Dunlop Motor Co Ltd (1907)) and Stringfellow v McCain Foods GB Ltd (1984)。 Nor can it be used where the name consists of a word in general use (Aerators Ltd v Tollitt (1902))。

　　Part 41 of the Companies Act (CA) 2006， which repeals and replaces the Business Names Act 1985， still does not prevent one business from using the same， or a very similar， name as another business so the tort of passing off will still have an application in the wider business sector. However， the Act introduced a new procedure to deal specifically with company names. As previously under the CA 1985， a company cannot register with a name that was the same as any already registered (s.665 Companies Act (CA) 2006) and under CA s.67 the Secretary of State may direct a company to change its name if it has been registered in a name that is the same as， or too like a name appearing on the registrar‘s index of company names. In addition， however， a completely new system of complaint has been introduced.