The Standard Industrial Classification (SIC) is a system for classifying the economic activities of a company by a code. They help various government bodies including Companies House define what the company does. You can find a condensed list of SIC codes at http://resources.companieshouse.gov.uk/sic/
You need at least one SIC code when incorporating a new company, to describe the company’s planned business activity. Companies House will reject your request to form a new company unless a SIC code is included. A SIC code is also required when completing and filing the confirmation statement for your company.
When choosing your SIC code you will find that they are organised into sections which group together similar trade classifications. The “Information and Communication” section for example groups together 32 different SIC codes, and these range from “book publishing” all the way to “Computer facilities management activities” so you will need to review these and select a code carefully. The code chosen by a company is available for anyone to view on the public record once the company has been incorporated.
If your company’s activities are particularly complex and a single code doesn’t describe the full nature of the company’s business activities, you can choose to include more than one. Most companies opt for a single SIC code to expresses the nature of their business but you can choose up to four SIC codes.
You can amend your SIC code or add another if you feel the need to do so. If you find that the code you selected at incorporation does not reflect the company’s activities after the initial trading experience or you previously entered an incorrect code, it can be changed. All you need to do is change it the next time your confirmation statement is due or you can file an updated confirmation statement before the due date.