A SIC code (Standard Industrial Classification code) is a five-digit number that describes what a UK company does. Every company registered at Companies House must have at least one SIC code, per Companies House. It determines how your business is categorised for statistical, regulatory, and benchmarking purposes — and it appears on the public Companies House register.
What are SIC codes used for in the UK?
SIC codes were introduced to give a standardised way of classifying business activity across the UK economy. In practice, they touch more of your day-to-day operations than most founders realise when they first pick one during incorporation.
Companies House uses SIC codes to categorise companies on its public register. When someone searches the register by industry, your SIC code determines whether you appear in the results. This matters if you want to be discoverable to potential partners, investors, or acquirers who search by sector.
HMRC uses SIC codes for industry benchmarking. When your Corporation Tax return is filed, HMRC compares your margins, cost structures, and profit ratios against sector averages for companies with the same SIC code. An unusual profit pattern for your stated sector can increase the likelihood of HMRC scrutiny — not because a wrong SIC code is an offence in itself, but because mismatched benchmarks can flag anomalies.
Where SIC codes matter operationally
- · Companies House public register and searches
- · HMRC industry benchmarking for Corporation Tax
- · Business bank account applications (some banks restrict certain codes)
- · Insurance underwriting and premium calculation
- · Government statistical data and ONS reporting
Where SIC codes have limited impact
- · No legal trading restrictions based on SIC code alone
- · Not used to determine VAT treatment
- · Not linked to employment law obligations
- · Not visible to customers in standard searches
- · No fine or penalty for a wrong code (but bank and HMRC friction apply)
How do you find the right SIC code for your business?
The definitive source is the Companies House SIC code list, which uses the UK SIC 2007 system — a condensed version of the ONS classification adopted by Companies House. The list is searchable by keyword; entering "consulting", "software", "cleaning", or your primary activity usually narrows it to a shortlist of 3–6 candidates.
You can register up to four SIC codes per company, per Companies House. The primary code should reflect the activity that generates the majority of your revenue. Additional codes can cover meaningful secondary activities, but there is no value in padding the list — picking irrelevant codes can create the same HMRC benchmarking friction as picking wrong primary codes.
A practical approach: identify your primary revenue stream first and find its best SIC code match. Then consider whether any secondary revenue streams are material enough (roughly 10%+ of turnover) to warrant a second code. If you are genuinely a multi-activity business — a firm that both develops software and provides consultancy, for example — codes 62012 and 70229 used together accurately reflect that without confusion.
What are the most common SIC codes for UK businesses?
The following ten codes cover a large proportion of the UK's small business registrations. If your business falls broadly into one of these sectors, start here — but always verify against the Companies House full list, as the descriptions below are summaries.
| SIC Code | Description | Common use |
|---|
| 62012 | Business and domestic software development | Software developers, SaaS companies, app studios |
| 69201 | Accounting and auditing activities | Accountancy firms, bookkeeping practices |
| 70229 | Management consultancy (other) | Business consultants, strategy advisers |
| 47910 | Retail sale via mail order or internet | E-commerce businesses, online retailers |
| 41100 | Development of building projects | Property developers, residential and commercial |
| 85590 | Other education not elsewhere classified | Tutoring, online courses, training providers |
| 86900 | Other human health activities | Private healthcare providers, physiotherapy |
| 74909 | Other professional, scientific and technical activities | Research, specialist professional services |
| 73110 | Advertising agencies | Marketing agencies, creative studios |
| 68100 | Buying and selling of own real estate | Property investment companies, landlords (via SPVs) |
Can you change your SIC code after registering?
Yes. You can update your SIC code at any time by filing your annual confirmation statement with Companies House. The confirmation statement (formerly the annual return) includes a section for reviewing and updating your SIC codes — you simply amend the entry at the time of filing. There is no specific fee for changing just the SIC code, though the confirmation statement itself costs £34 if filed online, per Companies House (£62 if filed by paper).
You can also request a change to your SIC code outside the annual confirmation statement cycle if your business activity has changed materially mid-year. In this case, contact Companies House directly. There is no regulatory penalty for having had a wrong code in the past — the change is prospective, not retrospective, and Companies House does not pursue historical misclassification.
The practical rule is to keep your SIC codes updated whenever your primary revenue stream changes. A software agency that pivots to pure SaaS should update 70229 (if used) and add or switch to 62012. A holding company with dormant operational subsidiaries might legitimately use 64202 (activities of other holding companies) at parent level while subsidiaries carry their own operational codes.
What happens if you have the wrong SIC code?
There is no legal offence of having the wrong SIC code and no direct Companies House fine for misclassification. However, the downstream effects are real enough that it is worth getting right from the start. The two most common practical problems are bank account friction and HMRC benchmark mismatches.
Bank account friction is the most immediate issue. Many UK banks use SIC codes as part of their risk-assessment process for new business accounts. Certain codes — typically those associated with high-risk financial activity, adult content, gambling, or complex financial structures — can cause automatic flags or declines at the account opening stage. Picking a code that does not accurately reflect your activity, either too broadly or too specifically, can trigger unnecessary due diligence.
HMRC benchmarking mismatches arise because HMRC uses your SIC code to compare your accounts against sector norms. A management consultancy coded as software development may show margins that look anomalous for a software business, increasing the probability of HMRC enquiry. This does not mean you will be investigated — it means your account is more likely to be flagged for review, which means more professional fees and management time even if the outcome is favourable.
For formation support and help selecting the right SIC code from the start, Verity Partners handles company formation and early-stage compliance. See also the guide to setting up a UK limited company and the starting a business resources hub.
Frequently asked questions
Is a SIC code the same as a NACE code?
No, but they are related. The UK SIC 2007 code system is based on the EU NACE Rev.2 classification, which in turn is based on the UN ISIC system. UK SIC codes are five digits; NACE codes are four digits. UK SIC 2007 is more granular than NACE — it subdivides some NACE categories. Since Brexit, UK SIC codes have diverged slightly from EU NACE, though most codes remain identical.
Do I need a SIC code before I start trading?
Yes. SIC codes are required at the point of incorporation — you must enter at least one when you register via Companies House, per Companies House guidance. You cannot leave the field blank on the IN01 incorporation form. If you are not sure at the time of incorporation, pick the closest available code and update it via your first confirmation statement.
Can a holding company have the same SIC code as its subsidiaries?
It can, but it usually should not. Holding companies that purely own and control subsidiaries without trading themselves typically use code 64202 (activities of other holding companies not elsewhere classified) or 70100 (activities of head offices). Using an operational code at holding company level when the holding company does not itself conduct that activity can create the HMRC benchmarking mismatches described above.
What SIC code should I use if my business does several different things?
Use the code that best describes the activity generating the majority of your revenue as your primary code, and add up to three further codes for significant secondary activities. Per Companies House, you can have up to four SIC codes simultaneously. Prioritise accuracy over comprehensiveness — most businesses with diverse activities are best served by one or two codes that genuinely reflect the core business.
How do I check a company's SIC code?
All SIC codes for UK companies are publicly available on the Companies House register at find-and-update.company-information.service.gov.uk. Search by company name or number and the company overview page shows all registered SIC codes. There is no charge to view this information. This is useful for researching competitors, potential suppliers, or acquisition targets.