SIC codes explained: how to pick yours in 2 minutes

Short answer: a SIC code is a five-digit number that tells Companies House what your business does. Pick the one that most closely describes your main activity, add up to three more if you genuinely do several things, and move on. It is not a tax election, it doesn't restrict what you're allowed to do, and you can change it at your next confirmation statement.

People lose far more time on this than it deserves. Here is what actually matters.

What a SIC code is for

SIC stands for Standard Industrial Classification. Companies House uses it to categorise every company on the register so that meaningful statistics can be produced about the UK economy — how many construction firms there are, which sectors are growing, and so on.

You choose from a fixed list maintained by Companies House. You must provide at least one when you incorporate, and you confirm your codes each year on your confirmation statement.

What it does not do

This is where the anxiety comes from, so let's clear it out:

• It does not limit what your company can legally do. Modern companies have unrestricted objects. Your SIC code says what you do, not what you're permitted to do.
• It does not determine your tax treatment. HMRC taxes your actual profits, not your classification.
• It does not need to change every time you take on a slightly different project.

How to choose in two minutes

1. Describe your main activity in one plain sentence. "We install kitchens." "We provide bookkeeping services." "We sell secondhand books online."
2. Search the Companies House SIC list for the main noun or verb in that sentence.
3. Pick the closest match. Close is fine. Exact is not required and often not available.
4. Add up to three more only if you genuinely have distinct revenue streams.
5. Done.

If nothing fits, there are general "other" codes designed exactly for that situation. Using one is not a failure.

Why you can have four

Because plenty of businesses genuinely do more than one thing. A firm that does both accountancy and payroll, or a shop that also runs a café, has more than one real activity.

But list the ones you actually do. Four codes covering activities you're merely thinking about makes your public record less accurate, not more impressive.

Order matters slightly: put your main activity first. Some data users treat the first code as the principal one.

Where people go wrong

Choosing an aspirational code. You're a consultant today; listing software publishing because you might build an app one day just makes your record wrong.

Choosing a vague code to keep options open. Dormant and "non-trading" codes exist for companies that genuinely aren't trading. Using one while you are trading is inaccurate, and it can look odd to anyone running due diligence on you.

Assuming banks don't look. Some do. A mismatch between your SIC code and what you tell your bank you do is the sort of thing that triggers questions during onboarding — not usually fatal, but an avoidable delay.

Agonising. The most common error by a distance. Your SIC code is one of the lowest-stakes decisions in the whole incorporation process.

Changing it later

Straightforward. You update your SIC codes when you file your confirmation statement, which you do at least once every 12 months. There is no separate form and no extra fee.

If your business genuinely pivots, update it at the next statement. There is no need to file anything early.

Quick answers

How many do I need? At least one, up to four.

What if my business is brand new and doing nothing yet? There are specific dormant and non-trading codes for that. Use one, and change it when you start trading.

Does my SIC code affect my chances of getting a business bank account? It shouldn't determine the outcome, but some sectors attract more scrutiny, and an inaccurate code creates an inconsistency you'll have to explain. Accuracy helps you here.

Can two companies have the same code? Yes — thousands do. It's a classification, not an identifier.

Is it on the public record? Yes, visible on your company's Companies House page.

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