Many businesses have clear guidelines about the type of things that their staff should leave out of work e-mails, without realising that they also need to pay attention to what is included.

Under UK law, most large companies must include certain basic information about themselves in any e-mails they send.

The Companies (Trading Disclosures) Regulations carry the risk of a £1,000 fine for noncompliance, swelled by £100 for each day that the company continues to breach the rules.

They are also to blame for the long lines of text that are becoming a common feature at the bottom of business e-mails.

The laws, which were updated this month, cover all private and public companies and limited liability partnerships. Sole traders and standard partnerships are exempt.

All companies covered by the regulations must include four basic pieces of information on emails: the company's registered name; where in the UK it is registered; its registration number; and the address of its registered office.

This may seem simple, but a recent survey from Dotmailer, an internet marketing business, found that almost half of retailers had e-mailed potential customers without including the required information.

In practice, however, a closer look at the regulations shows that they do not fully apply to every e-mail that a company sends.

So, while business letters need all the information, an e-mailed invoice, for instance, needs only the company's registered name.

Despite this, lawyers say that companies can save themselves a headache by configuring their IT system to add all the information to all e-mails as standard.

Jonathan Cornthwaite, a partner at Wedlake Bell, the law firm, said: “It's true that some emails do not need everything, but most companies will find it easier to have a uniform disclosure paragraph for all their business e-mails, rather than having to distinguish between different kinds of e-correspondence each time.”

The rules do not stipulate where the information should go - most companies opt for the bottom of the e-mail - but they do ban companies from making it too small, with a requirement that the obligatory information be included so that “it can be read with the naked eye”.

Likewise, the rules say that companies that are part of a larger group cannot restrict their disclosures to details of the parent company but must include particulars of the subsidiary that sends the e-mail.

This may sound like yet another business burden, but lawyers remind companies that automatic e-mail add-ons can also be a blessing.

One common type is a disclaimer, which, with a quick word to the IT department, can offer companies a crucial layer of protection from disgruntled customers.

Disclaimers will vary in effectiveness according to the type of business involved and the relationship with the recipient, but Mr Cornthwaite said that one broad type can state that since e-mail is a non-secure form of communication and is open to data corruption, none of the contents should be relied on without double-checking with the sender.

Published on the Times Online, 25 February 2009