What is a SIC code?
It stands for Standard Industrial Classification. Think of it as the label on your company's file at Companies House, saying "this one builds websites" or "this one cuts hair".
Companies House keeps a shortened list of these codes, and only codes from that list count. When we checked on 31 July 2026 the list held just over 730 of them. If you send a code that is not on the list, your filing can bounce back.
A few real examples so you can see the shape of them:
- 62020 Information technology consultancy activities
- 43999 Other specialised construction activities
- 56101 Licenced restaurants
- 93130 Fitness facilities
- 47910 Retail sale via mail order houses or via Internet
Where does mine come from, and who looks at it?
You chose one when you set the company up. Whoever did the registration, you or a formation agent, had to put a code in the box before Companies House would issue the certificate.
After that it sits on the public register next to your company name, and it stays there until you change it. Banks, lenders and insurers read it. Companies House uses the codes to count how many companies work in each industry across the UK.
How many can my company have?
At least one. You can hold up to four if your company does a few different things.
A company that fits gardening, garden design and a small plant shop can carry a code for each. Put the one that earns you the most money first. If one code covers nearly everything you do, one is enough, and adding three more does not help you.
Does my SIC code change my Corporation Tax bill?
No. Your tax rate comes from your profit, not from your trade.
Two companies, each the only company its owner has, both with £40,000 of profit for the year:
| Bright Pixel Ltd | Hedge and Home Ltd | |
|---|---|---|
| SIC code | 62020, IT consultancy | 81300, landscape service activities |
| Profit for the year | £40,000 | £40,000 |
| Rate that applies | 19% | 19% |
| Corporation Tax due | £7,600 | £7,600 |
The codes differ and the bill does not. Profits of £50,000 or less pay 19%, profits above £250,000 pay 25%, and anything in between gets partial relief. Your industry never enters that sum.
Two things can pull those £50,000 and £250,000 lines down: owning or controlling more than one company, and an accounting period shorter than 12 months. Both are about how your companies are set up, not about what any of them do, so your SIC code still has nothing to do with it.
There is one honest caveat worth knowing. A handful of special tax rules do turn on what a company does, such as oil and gas extraction, or a research and development claim. Those follow the real work rather than the code typed on the register, so switching your code would not move you in or out of them.
What code does a dormant company use?
99999. Its official name on the list is "Dormant Company", and even a company doing nothing at all still has to give a code.
There is a second one people mix up with it. 74990 is labelled "Non-trading company", so it belongs to a company that exists but does not trade.
The mistake worth avoiding is leaving 99999 in place after your company starts earning. Companies House picks that up as one of the most common wrong entries on the register, and it can draw a look at your file. If you are trading, move off 99999.
For what a dormant company actually has to send to each body, read My company is dormant, what (if anything) do I file?
What about the vague catch-all codes?
Codes like 82990 ("Other business support service activities") and 96090 ("Other service activities") are real codes on the list, and the "n.e.c." you sometimes see after them means "not elsewhere classified". They exist for work that genuinely fits nowhere else.
Use one if nothing better fits. Reach for a specific code first, because a vague code tells a lender and Companies House very little about you.
Watch out for 74990 here. Plenty of blogs describe it as a general "other business activities" code, and at Companies House it means non-trading. A trading company should not park itself on it.
I picked the wrong one. Am I in trouble?
No. A code that does not match your work is not a tax offence and it does not create a penalty on its own. Companies House can question, reject or remove register entries that look wrong, so fix it rather than sit on it. Choosing an imperfect code by accident is a different thing from putting something false on the register on purpose, and only the second one gets you into real trouble.
How do I change it?
On your confirmation statement. There is no separate "change my SIC code" form to hunt for. You update the code in the same yearly filing that confirms your address, directors and shareholders.
If you do not want to wait for the next one, you can file a confirmation statement early and change the code then. You pay the fee once in a 12-month period, so an early one inside a period you have already paid for costs you nothing extra.
For how that filing works, its deadline and what else it covers, read The confirmation statement: what it is and isn't.
Does HMRC care about my SIC code?
Your SIC code belongs to Companies House. HMRC works out your tax from the figures in your return, not from a classification code on the register.
If you are unsure which body wants what from you, read Companies House vs HMRC: what's the difference and what do I send each?
How SimpleReturns handles it
We prepare your accounts and your Company Tax Return from your year's money in and out. Your SIC code plays no part in the figures we calculate, and changing it will not change a number on your return. Keeping the code itself up to date is a Companies House job, and it happens on your confirmation statement.