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When you form a company, you pick one or more SIC codes from a long list and rarely think about them again. That is a mistake more often than people expect. This guide explains why SIC codes matter, who reads them, what goes wrong when they no longer match what your business does, and how to choose the right ones.
What a SIC code is
SIC stands for Standard Industrial Classification. Each code is a five-digit number describing a type of business activity, such as 62020 for information technology consultancy or 56101 for licensed restaurants. Companies House uses a condensed list of more than 600 codes grouped into 21 broad sections. Every company must have at least one code and can have up to four.
Two codes have special meanings: 99999 for a dormant company and 74990 for a non-trading company. Even a company that is not doing anything must give one.
Why SIC codes matter: who reads them
Lenders and funders
Banks, lenders and grant schemes use your SIC code to decide whether you are eligible and how risky you look. Some funding is only open to certain industries. If your code says you are a holding company and you apply for a hospitality grant, expect questions, delays or a refusal.
Insurers
Insurers check that the activity on your policy matches the activity on the register. A mismatch can slow down a claim at exactly the moment you need it paid.
Customers and suppliers
Larger customers, credit reference agencies and suppliers offering you credit all look at the public register. A code that does not match your website or invoices raises doubts about whether the company is what it says it is.
Government
Companies House, HMRC and the Office for National Statistics use SIC codes to understand the economy and to spot companies whose details do not add up. Since 2024, Companies House has had stronger powers to query, reject or remove information that looks wrong or misleading, and a code that does not fit your activity can lead to filings being questioned or delayed.
What goes wrong with an out-of-date code
Businesses change. A web design company starts selling software, a consultancy opens a shop, a property company starts letting holiday homes. If the SIC code stays the same, the register tells the world the old story. The common results are:
- a loan or grant application that stalls while the lender asks why your activity has changed
- an insurer querying a claim because the policy and the register disagree
- a bank's checks flagging the account for review
- a supplier declining credit because the company looks inconsistent
- a dormant code (99999) left in place after you have started trading, which suggests the company is not being run properly
How to choose the right SIC codes
Start with what earns the money. Your first code should describe your main activity, the one that brings in most of your income. Then add up to three more for other significant activities, not for everything you might do one day.
- Be specific. Pick the most precise code that fits rather than a general "other" code.
- Describe what you do, not who you serve. An accountant serving restaurants uses an accounting code, not a restaurant code.
- Match your other records. Your website, insurance and bank account should tell the same story as the register.
- Review it yearly. Your confirmation statement is the natural moment to check the codes still fit.
Changing your SIC codes
You change SIC codes by filing a confirmation statement with the new codes. You do not have to wait for the yearly one: you can file a statement early at any time to update them. Companies House charges its £50 fee only once in each 12-month payment period, so if you have already paid this period, an extra statement to change your codes costs nothing in Companies House fees. Our guide to updating your business activity walks through it step by step.
A new SIC list is on its way
The Office for National Statistics has published a new classification, UK SIC 2026, to reflect activities that barely existed when the current 2007 list was written. Companies House has said that moving the register to new codes needs a change in the law, and no date has been set. Until it is, keep using the current list. When the switch comes, companies will be told what to do.
How we can help
If your company's activity has changed, our update business activity service finds the right codes for what you do now and files the change with Companies House for you. We can also check your codes as part of your confirmation statement filing.
