When you register a limited company in the UK, you must choose at least one five-digit SIC code that describes what your company does. You can choose up to four codes, but the first one must be your main activity. Pick it from Companies House’s condensed list, not from a general internet list, or your filing may be rejected.
It is a small box on the form, and most founders rush it. That is a mistake: your SIC code sits on the public register, tells banks, insurers and customers what your business does, and stays with you until you update it on a confirmation statement. This guide explains what a SIC code is, how to choose the right one, and which mistakes to avoid.
If you have not started the process yet, begin with our step-by-step guide to register a limited company in the UK and come back here when you reach the “nature of business” section of the form.
What is a SIC code?
SIC stands for Standard Industrial Classification: five-digit codes, maintained by the Office for National Statistics, that classify every kind of business activity, from growing cereals to writing software. Companies House uses a condensed version of the full UK SIC 2007 list, and that condensed list is the only list that counts for your filing — a code in the full ONS list but not in the condensed list will not be accepted.
Your SIC code is not a licence, a tax status or a permission to trade. It does not change your corporation tax rate, and it does not limit what your company is legally allowed to do. It is a classification: a public, standardised way of saying “this is the kind of business we are”. That matters because banks, insurers, suppliers and customers checking you on Companies House will all see the same short description of your business.
How many SIC codes do you need?
Every limited company must provide at least one SIC code when it registers. You may provide up to four, with the first code as your main activity — the activity bringing in most revenue, or, if not yet trading, the activity you intend to start with.
Most small companies need just one code. If you run a single, clear business — a consultancy, a shop, a cleaning firm — one accurate code is better than four approximate ones. Extra codes are for genuinely distinct activities, such as a software firm that also sells training courses. Padding the list with codes for things you might do one day only muddies the public record.
Two special codes cover companies that are not trading yet. A dormant company — one with no significant transactions — uses 99999. A company registered but not yet trading uses 74990. You still need a code in both cases; when the company starts trading, update it on your next confirmation statement.
How to choose the right SIC code in 4 steps
Step 1: Describe what you actually do, in one sentence. Not what your website says, and not what you hope to expand into. “We build websites for small businesses” is a good starting sentence. “We are a digital solutions company” is too vague to match a code.
Step 2: Search the condensed list by keyword. Search for the key word in your sentence — “software”, “consultancy”, “cleaning”, “retail” — which usually narrows hundreds of codes to a shortlist of three to six. Read the full description of each candidate, not just the heading: two codes can differ in one important word, such as “licensed” versus “unlicensed” for restaurants, or “letting” versus “buying and selling” for property.
Step 3: Put your main activity first. If you have more than one genuine activity, order the codes by importance, with the main one first. The first code is the one most readers, and most automated checks, will treat as your business type. Do not put a side activity first because its code sounds more impressive.
Step 4: Check before you file. Confirm every code appears on the condensed list, that you have spelled the five digits correctly, and that the descriptions still match your sentence from step 1. A single wrong digit can land you in a completely different industry.
For the official list itself, use the Companies House condensed SIC code list — it is the version Companies House actually checks your filing against.
Common SIC codes for small businesses
| Business type | SIC code | Official description (shortened) |
|---|---|---|
| Software developer / SaaS company | 62012 | Business and domestic software development |
| IT consultant | 62020 | Information technology consultancy activities |
| Management consultant | 70229 | Management consultancy activities (other than financial management) |
| Accountant | 69201 | Accounting and auditing activities |
| Online retailer | 47910 | Retail sale via mail order houses or via the internet |
| Advertising agency | 73110 | Advertising agencies |
| Licensed restaurant | 56101 | Licensed restaurants |
| Café (unlicensed) | 56102 | Unlicensed restaurants and cafés |
| Buy-to-let property company | 68209 | Other letting and operating of own or leased real estate |
| Property developer (buying and selling) | 68100 | Buying and selling of own real estate |
Use this table as a starting point, not as a substitute for checking the list. Descriptions here are shortened, and the condensed list is the authoritative wording. Property is where founders most often pick the wrong code: a company letting out property it owns should not use the buying-and-selling code, and vice versa. Lenders pay attention to this distinction for buy-to-let mortgages, so get it right at registration.
Worked examples: choosing codes for real businesses
| Business | Codes to choose | Why |
|---|---|---|
| Freelance software developer who also advises clients on IT systems | 62012 first, then 62020 | Software development is the main income; consultancy is a genuine second activity |
| Consultant who sells an online course as a side line | 70229 only, at first | Consultancy is the business; a small side product does not yet justify a second code |
| Company buying houses to let out long term | 68209 | Letting its own property, not buying and selling for a quick profit |
| Company buying, renovating and selling houses | 68100 | Buying and selling its own real estate is the activity itself |
| Registered company, not yet trading | 74990, then update later | Non-trading code until trading starts; switch to the real activity code on the confirmation statement |
5 SIC code mistakes founders make
1. Copying a competitor’s code without checking. Two businesses can look similar and need different codes — a marketing freelancer and a marketing agency, or a shop selling online and one with high-street premises, may sit in different classifications. Check your own activity, not someone else’s filing.
2. Using a code from the full ONS list that is not on the condensed list. This is the most common technical rejection. Companies House checks against its condensed list only, so a code not on it may be rejected, however accurate it looks elsewhere.
3. Picking the broadest “n.e.c.” code as a shortcut. Many codes end in “n.e.c.”, meaning “not elsewhere classified”, for activities with no specific code. Using one when a specific code exists makes your public record vaguer than it needs to be, and can confuse lenders and insurers.
4. Listing every activity you might ever do. Four codes used to cover four real activities is fine. Four codes used to cover one real activity and three ideas is not. Keep the list honest, and add codes later, when the new activity actually starts, through a confirmation statement.
5. Forgetting to update the code when the business changes. Companies pivot: a shop becomes a wholesaler, a consultancy becomes a software company, a dormant company starts trading. Because the code is only reviewed on the confirmation statement, it is easy to let it drift years out of date — and a stale code is the one a bank or customer sees first.
How to change your SIC code later
You change a SIC code by filing a confirmation statement (form CS01) with Companies House. There is no separate SIC-change form. You must file a confirmation statement at least once every 12 months, and you can file one early if your details change sooner. Each year, before you file, ask one question: does our SIC code still describe what we actually do? If not, update it in the same filing.
Frequently asked questions
Do I need a SIC code if my company is dormant?
Yes. A dormant company uses 99999, and a non-trading company uses 74990. Every company on the register must have at least one code, even if it is not trading yet.
Can I change my SIC code after registering?
Yes. Update it on your next confirmation statement (form CS01), or file a confirmation statement early if you want the change made sooner. There is no separate form just for SIC codes.
Does my SIC code affect how much tax I pay?
No. Your SIC code does not set your corporation tax rate or your VAT treatment. It is a classification for the public register and for statistics. A wrong code can still cause practical friction with lenders or insurers, so it is worth getting right, but it does not change your tax bill by itself.
What happens if I pick the wrong SIC code?
Usually nothing dramatic straight away — but your public record will describe the wrong business, and a lender, insurer or customer who checks it may be confused or ask awkward questions. Correct it on your next confirmation statement, or file one early.
Conclusion
Choosing a SIC code is one of the smallest decisions in registering a limited company, and one of the easiest to get right. Describe what you actually do, search the Companies House condensed list by keyword, put your main activity first, and check every digit before you file. One accurate code beats four vague ones, and a code reviewed every year will never drift far from the business it describes.
