SIC Codes on the Company Register: What They Tell You, and What They Do Not

Look at almost any company on the public register and you will find one or more five-digit numbers describing what the business does. These are Standard Industrial Classification codes, or SIC codes. They are useful for a first look at a company, but they are easy to over-read. This guide explains what they are and what they cannot show. It is information only and is not a statutory audit, assurance engagement or substitute for professional verification.

What a SIC code is

GOV.UK describes the list as a way to classify business establishments and other standard units by the type of economic activity in which they are engaged. The full classification is published by the Office for National Statistics as UK SIC 2007. Companies House uses a condensed version of that list, and companies describe the nature of their business using those codes.

How the codes are used at filing

The condensed list is available as a CSV file and through an online SIC code lookup. Companies House gives a clear instruction to filers: use only the SIC codes on the condensed list, or the filing may be rejected. In practice, that means the codes on the register come from a controlled menu, not free text.

What the code can tell you

• A broad category. It gives a quick idea of the sector a company says it operates in.
• A consistent label. Because the list is standard, you can compare like with like across many records.
• A starting point. It helps you decide which other documents to read next.

What it cannot tell you

The GOV.UK page explains that companies provide the description of their nature of business. It does not say anyone has checked that description against what the company does day to day. So treat a SIC code as a self-described label. It does not show what a company sells, who its customers are, whether it is trading or whether it holds any particular permission. A company can also change its codes over time, and several codes can be listed together.

A simple way to read a SIC code

1. Note the code and look it up in the condensed list so you read the right description.
2. Compare it with other sources you already have, such as the company's website or accounts.
3. If the description and the other sources disagree, write down both and ask the company which is current.
4. Record the date you looked and where you saw the code.

Common slips to avoid

• Treating a code as proof that a company is regulated, or is not.
• Searching for a company by a code and assuming the results are a complete list of firms in that trade.
• Forgetting that a code describes a classification, not quality or standing.

The short version

SIC codes are a handy label drawn from a standard list, chosen by the company and constrained by what Companies House accepts. Use them to orient yourself, then look at the filing history, accounts and other records for the detail. Audit1 provides general information only; for anything that matters, ask a qualified professional.