A SIC code – short for Standard Industrial Classification code — is a five-digit number that tells Companies House what industry your business operates in. If you have registered, or are registering, a limited company in the UK, you are legally required to provide at least one SIC code. Think of it as a label that puts your business into the right category — so that the government, banks, and other organisations know what you actually do.
If you have ever stared at the SIC code field during company formation and had no idea what to pick, you are not alone. This guide explains everything you need to know in plain English — no jargon, no complexity.
What Does SIC Stand For?
SIC stands for Standard Industrial Classification. In the UK, these codes are maintained by the Office for National Statistics (ONS) and used by Companies House to classify and record what businesses do.
The current version used in the UK is called UK SIC 2007. It was introduced in January 2008 and updated from the previous 2003 version. Companies House made it compulsory for all companies to use the 2007 list from October 2011. As of 2024, this remains the most recent version in use.
The full ONS list contains over 700 five-digit codes. Companies House uses a condensed version of this list, and you must only use codes from that condensed list when filing — otherwise your application or confirmation statement may be rejected.
Why Does the Government Use SIC Codes?
SIC codes serve as a statistical tool. The government uses them to track economic activity across different industries — seeing which sectors are growing, which are struggling, and where the economy is heading. But their use goes beyond statistics.
Here is who uses your SIC code and why:
- Companies House — to classify your business when it is incorporated and to record it on the public register
- The Office for National Statistics (ONS) — to analyse industry trends and publish economic data
- HMRC — to risk-profile tax credit claims, including R&D tax credits, and to identify businesses likely to be in certain sectors
- Banks and mortgage lenders — to decide whether your company qualifies for certain products or loans
- Credit reference agencies — to assess the nature and risk profile of your business
So while a SIC code might seem like a minor administrative detail, getting it right actually matters quite a lot.
What is a SIC Code Used For in Practice?
When you register a company at Companies House, you are asked to choose between one and four SIC codes. These codes tell people who look up your company on the Companies House register what your business does.
Your first SIC code should reflect your main business activity — the one that generates the most revenue. Any additional codes can describe secondary activities, but you should only include them if they genuinely represent a significant part of what your company does.
How Does HMRC Use My SIC Code?
HMRC does not use SIC codes to calculate your tax bill directly, and the code does not appear on your company tax return (CT600). However, HMRC does use your SIC code to risk-profile claims.
For example, if a company claims R&D tax credits, HMRC will look at the SIC code to check whether the claim matches the type of business on record. A software company with a software development SIC code is far less likely to attract scrutiny than one with a mismatched code. Getting the right code from the start protects you from unnecessary questions later.
How Do Banks and Mortgage Lenders Use My SIC Code?
This is where an incorrect SIC code can cause real problems. Banks use SIC codes when assessing applications for business bank accounts, loans, and mortgages.
A common example involves property companies. If you set up a buy-to-let limited company and choose the wrong SIC code, most mortgage lenders will automatically decline your application. Buy-to-let limited companies should use SIC code 68209 (letting and operating of own or leased real estate). Using code 68100 (buying and selling of own real estate) instead marks your company as a property trader, which carries a very different risk profile in the eyes of lenders.
Similarly, online retailers should use SIC code 47910 to avoid issues with payment processing providers.
How Many SIC Codes are There in the UK?
The Companies House condensed list covers over 700 five-digit codes. These are grouped into 21 broad industry sections, each represented by a letter from A to U. Within each section, codes are organised by divisions, groups, classes, and subclasses.
Here is a high-level overview of the 21 sections:
- A — Agriculture, Forestry and Fishing
- B — Mining and Quarrying
- C — Manufacturing
- D — Electricity, Gas, Steam and Air Conditioning Supply
- E — Water Supply, Sewerage and Waste Management
- F — Construction
- G — Wholesale and Retail Trade
- H — Transportation and Storage
- I — Accommodation and Food Service Activities
- J — Information and Communication
- K — Financial and Insurance Activities
- L — Real Estate Activities
- M — Professional, Scientific and Technical Activities
- N — Administrative and Support Service Activities
- O — Public Administration and Defence
- P — Education
- Q — Human Health and Social Work Activities
- R — Arts, Entertainment and Recreation
- S — Other Service Activities
- T — Activities of Households as Employers
- U — Activities of Extraterritorial Organisations
Most small business owners and the self-employed will find their activity in sections G, J, K, L, M, N, or S. If your business fits neatly into a specific category, choose the most precise code available rather than a general catch-all option.
How Do I Find the Right SIC Code for My Business?
Finding your SIC code is a straightforward process once you know where to look. Follow these steps:
- Go to the Companies House SIC code tool at resources.companieshouse.gov.uk/sic/ — this is the official condensed list you must use.
- Search for a keyword that describes your main business activity. Try simple terms like ‘accountant’, ‘builder’, ‘consulting’, ‘retail’, or ‘software’.
- Review the results and pick the code with the description that most closely matches what your business actually does.
- If you cannot find an exact match, look up similar businesses on the Companies House public register to see which code they have used.
- If you are still unsure, speak to an accountant — getting it right first time saves you from problems with banks, HMRC, or lenders later on.
What If I Cannot Find an Exact Match?
Not every business activity has its own dedicated SIC code. If you cannot find a perfect match, choose the code that most closely describes your primary activity. Avoid using vague, catch-all codes such as 74990 (non-trading company) or 82990 (other business support service activities) unless nothing else fits. The closer your code is to your actual trade, the better.
Companies House has not historically penalised businesses for choosing a broadly similar code in good faith. However, as mentioned above, a mismatched code can cause practical problems with third parties like banks and HMRC, so it is worth taking the time to get it right.
Can I Have More Than One SIC Code?
Yes. Companies House allows you to register up to four SIC codes per company. This is useful if your business genuinely covers more than one distinct activity.
For example, a business that offers both IT consulting and software development might use two separate codes — one for consultancy (62020) and one for software development (62012). The key word here is ‘genuinely’. Do not add codes for minor or occasional activities — keep your codes relevant to what your company actually does on a regular basis.
One important exception: be careful with multiple SIC codes for property activities. Having more than one property-related code can sometimes create confusion for HMRC, mortgage lenders, and other finance providers. If your company is involved in property in any way, we would recommend speaking to an accountant before choosing your codes.
How Do I Change My SIC Code?
If your business changes direction, or if you realise you are using the wrong code, you can update your SIC code at any time. The process is simple:
- Log in to Companies House WebFiling using your company authentication code
- File a Confirmation Statement (form CS01)
- Update your SIC codes in the relevant section
- Submit the statement — the change will appear on the register once processed
You do not need to wait until your next annual confirmation statement is due. You can file an early statement at any point during the year if you need to make an urgent correction.
There is no financial penalty from Companies House for having an incorrect SIC code. However, as this guide has explained, an incorrect code can still cause real-world problems — particularly with banks and HMRC. So if you know your code is wrong, it is always worth correcting it promptly.
What is SIC Code 99999?
SIC code 99999 is a dormant company code. If your company has been set up but is not currently trading, carrying out any business activity, or receiving income, you should use 99999. This tells Companies House — and anyone looking at the public register — that the company is dormant.
Once your company becomes active, you should update your SIC code to reflect your actual business activity at your next confirmation statement filing.
Are SIC Codes Publicly Visible?
Yes. Your company’s SIC code is part of the public record held at Companies House. Anyone can look up your company on the Companies House register and see the codes you have registered. This is useful for market research purposes — businesses and individuals regularly search the register to find companies operating in specific industries.
Because your SIC code is public, it also affects how your business is perceived. Investors, suppliers, and potential clients may look at it when researching your company.
Do Sole Traders Need a SIC Code?
No. SIC codes are only required for limited companies registered at Companies House. If you are operating as a sole trader or in a general partnership, you do not need a SIC code.
However, if you are thinking about moving from sole trader to limited company — which many business owners do for tax efficiency reasons — you will need to select a SIC code as part of the company formation process. This is one of the areas where speaking to an accountant before you make the switch can save you time and prevent costly mistakes.
Key Takeaways
- A SIC code is a five-digit number that classifies the industry your UK limited company operates in
- It is a legal requirement when incorporating a company at Companies House
- You can register between one and four SIC codes — your first should reflect your main business activity
- The current list is UK SIC 2007, maintained by the ONS and used in a condensed version by Companies House
- An incorrect SIC code can cause problems with banks, mortgage lenders, and HMRC — even if Companies House itself does not fine you
- You can change your SIC code at any time by filing a Confirmation Statement (CS01)
- Sole traders do not need an SIC code — it only applies to limited companies
Not Sure Which SIC Code to Use? We Can Help.
Choosing the right SIC code might seem like a small detail, but as this guide shows, it can have a real impact on your business — from HMRC queries to mortgage applications. If you are setting up a limited company, switching from a sole trader, or just want to check that your current code is correct, our team at Right Choice Consulting is here to help.
We offer straightforward accounting and tax support for business owners across the UK — no jargon, no unnecessary complexity. Get in touch today for a free initial conversation.
Disclaimer: All the information provided in this article is general in nature and it does not intend to disregard any of the professional advice.