Choosing a SIC code is one of the less glamorous parts of forming a UK company. You are thinking about your brand, website, customers and bank account, and then Companies House asks you to select a five-digit code describing what the business does. It is easy to pick the closest-looking option and move on. But what happens if you chose the wrong SIC code?

Usually, it is fixable. You do not need to close your company or incorporate again simply because you selected an incorrect SIC code. Companies House allows companies to update their SIC codes through the confirmation statement process. If necessary, you can file a confirmation statement early rather than waiting for the normal annual deadline.

However, SIC codes are more important than a box-ticking exercise. Companies House has recently emphasised that companies must keep their SIC information accurate, and it can challenge, reject or remove information that appears incorrect, inconsistent or misleading. This guide explains what a SIC code does, what happens when you choose the wrong one, how to change it and when an incorrect code could cause practical problems for your business.

What Is a SIC Code?

SIC stands for Standard Industrial Classification. A SIC code is a five-digit number used to describe the economic activity or activities carried out by a company. For example, a company involved in:

• software development
• management consultancy
• online retail
• property management
• advertising
• construction
• financial services

will generally need one or more SIC codes that correspond to its activities. Companies House uses a condensed list of SIC codes when companies file their information. The current official list is based on the UK Standard Industrial Classification system maintained by the Office for National Statistics. Companies House specifically says that only codes from its condensed list should be used when filing, otherwise an application may be rejected. A company can generally select up to four SIC codes where it carries out several different activities.

Does Choosing the Wrong SIC Code Matter?

Yes, but the seriousness depends on the type of mistake. If you selected a code that is reasonably close to what your company actually does, the immediate consequences may be limited. For example, imagine you formed a company intending to provide: Digital marketing and social media management, but selected a related advertising or marketing SIC code that does not describe the business as accurately as another available code.

That is different from a company actively trading as a software developer while its Companies House record says it is dormant. Companies House specifically warns that using dormant or non-trading codes for an active company is a common discrepancy and can attract scrutiny. The general principle is:

Your SIC code should give an accurate picture of what your company actually does.

It does not need to predict every product or service you might offer in five years, but it should not deliberately misrepresent your current activities.

What Happens If I Picked the Wrong SIC Code During Incorporation?

If the company has already been incorporated, you normally do not need to form a new company. You can update the SIC code when you file your next confirmation statement. Companies House specifically confirms that if you provide the wrong SIC code when setting up your company, you can update it when filing your next confirmation statement. If you want to change it sooner, you can file the confirmation statement early. This is an important point for new founders. An incorrect SIC code does not normally mean:

• your company is invalid;
• you need a new company number;
• you need to dissolve the company;
• your incorporation certificate becomes invalid; or
• you have to start the incorporation process again.

Instead, you should correct the information through the appropriate Companies House filing.

How Do I Change My SIC Code?

The normal mechanism is your confirmation statement. Companies House says the confirmation statement is used to confirm that company information is up to date. The SIC code is one of the pieces of information that can be changed through the confirmation statement.

Step 1: Identify what your company actually does

Before changing the code, write down the company's main activities in plain English. For example:

"We develop and sell subscription-based accounting software to small businesses."

Do not start by searching for a number. Start with the business activity.

Step 2: Search the official SIC list

Use the Companies House condensed SIC list rather than choosing a code based solely on a Google search or another company's filing. Companies House publishes the official condensed list specifically for companies filing their nature of business.

Step 3: Consider all significant activities

If your company carries out several activities, you can select up to four appropriate SIC codes. For example, a company might:

• develop software;
• provide IT consultancy;
• sell related digital products.

Depending on the exact activities, more than one SIC code may provide a more accurate picture. Do not add four codes simply because you are allowed to. Each code should correspond to a genuine business activity.

Step 4: File the confirmation statement

You can update the SIC information through the confirmation statement process. The current CS01 additional-information section specifically provides for adding new SIC codes and removing codes that no longer apply.

Step 5: Check the public record

After Companies House processes the filing, check the company's record to make sure the new SIC code is showing correctly. This final check is easy to overlook but useful, particularly if the correction is important for banking, funding or regulatory purposes.

Do I Have to Wait Until My Confirmation Statement Is Due?

No. This is one of the most useful things to know if you discover the mistake shortly after incorporation. Companies House states that you can file an early confirmation statement if you need to change your SIC code before the next scheduled confirmation statement. For example:

January: Company incorporated with the wrong SIC code.

February: Founder discovers the error.

Normal confirmation statement: Not due until the following year.

You do not necessarily have to wait a year to correct the code. You can file a confirmation statement early. There is a trade-off, however: filing early starts a new confirmation-statement review period from the new confirmation date. Companies House explains that when a confirmation statement is filed early, the next review period starts the day after the new confirmation date.

So if the error is minor and there is no practical reason for immediate correction, some companies may simply correct it at the next confirmation statement. If accuracy is important now, an early filing is available.

What If My Business Has Changed Since Incorporation?

This is slightly different from making an incorporation mistake. You may have chosen the correct SIC code when you formed the company but subsequently changed what the business does. For example:

Original business

A founder establishes a company providing graphic design services.

Six months later

The business moves into software development and no longer provides graphic design services. The SIC code may now need to be updated to reflect the company's current activity. Companies House explicitly says SIC codes should reflect what the company actually does and that companies should keep them accurate as activities change. This is why SIC-code maintenance is not simply an incorporation task. It is an ongoing company-record responsibility.

Can I Have More Than One SIC Code?

Yes. Companies House says a company can select up to four SIC codes if it carries out a range of different activities. Consider a company that:

• operates an online clothing store;
• designs its own clothing;
• provides fashion consultancy; and
• sells wholesale to retailers.

Depending on the precise activities, several SIC codes could potentially be relevant. The goal is not to find one magical code that covers the entire business. The goal is to provide an accurate classification of the company's principal and relevant economic activities.

Don't add irrelevant codes

More codes do not automatically make a company description better. Adding unrelated SIC codes simply because they might be useful in the future can make the company's record less accurate. Choose codes based on what the company actually does.

What If I Chose "Dormant Company" or "Non-Trading" by Mistake?

This deserves particular attention. Companies House identifies 99999 – Dormant Company and 74990 – Non-trading company as codes that can be used in appropriate circumstances. However, Companies House has specifically warned that using dormant or non-trading codes for an active company is a common discrepancy. If your company is actively trading but its SIC code suggests that it is dormant or non-trading, correct the record.

Example

Suppose: ABC Digital Ltd, is actively selling web-development services and receiving customer payments. But its Companies House SIC code is: 99999 – Dormant Company, That creates a clear mismatch between the company's actual activity and its public record.

The problem is not simply that the code is "not ideal." The company's stated classification contradicts what the business is actually doing. Companies House has said that inaccurate SIC information may attract scrutiny under its strengthened powers.

Can the Wrong SIC Code Affect Your Bank Account?

Potentially, yes. A SIC code is not the sole factor used by banks or financial institutions when assessing a company, and an incorrect code does not automatically mean a bank account will be refused.

However, banks, payment providers, insurers, lenders and other organisations may review a company's stated business activities as part of their onboarding or due-diligence processes. If your Companies House record says one thing while your website, application and actual transactions suggest something completely different, the inconsistency may lead to additional questions. For example:

Companies House: "Non-trading company"

Website: "Online financial technology platform"

Bank application: "Payment services"

That combination is likely to require explanation. An accurate SIC code therefore helps maintain consistency between your public corporate record and the business you actually operate.

Can the Wrong SIC Code Affect Business Funding?

It can be relevant. Companies House has specifically noted that a SIC-code mismatch could affect relationships with lenders or eligibility for certain funding. This does not mean that a particular SIC code automatically qualifies or disqualifies a company from funding.

Funding providers have their own criteria. However, if an organisation uses SIC information to understand the sector in which your company operates, inaccurate classification can create an incomplete or misleading picture. For startups seeking:

• business loans;
• grants;
• investment;
• sector-specific support;
• commercial partnerships;

keeping company information accurate is sensible.

Does the SIC Code Affect Corporation Tax?

The SIC code and Corporation Tax are related to the description of your company's activities, but they are not the same thing. Your SIC code does not itself calculate your Corporation Tax bill or determine your Corporation Tax rate. Tax treatment depends on the company's circumstances and the applicable tax rules.

However, your business activity is relevant to your tax obligations, and your company should provide accurate information to HMRC where required. Do not assume that changing your Companies House SIC code automatically updates HMRC records. Companies House and HMRC are separate organisations with different filing and tax responsibilities. If your business activity has changed significantly, review whether any separate tax, regulatory or accounting obligations have also changed.

Does a SIC Code Determine What My Company Is Legally Allowed to Do?

Not by itself. A SIC code describes the company's economic activity; it is not a licence granting permission to perform a particular activity. This distinction is particularly important for regulated industries. For example, selecting a SIC code associated with financial services does not automatically authorise a company to provide regulated financial services.

Similarly, choosing an appropriate SIC code for a healthcare-related business does not automatically satisfy sector-specific regulatory requirements. If your business operates in a regulated industry, you should separately check the relevant licensing and regulatory requirements. The SIC code is a classification, not a regulatory approval.

What If No SIC Code Seems to Fit My Business?

Modern businesses do not always fit neatly into traditional industry categories. This is especially common with:

• AI companies;
• digital platforms;
• creator businesses;
• SaaS startups;
• multi-service consultancies;
• ecommerce businesses;
• technology-enabled service companies.

Start by identifying the company's actual economic activity rather than trying to find a code that matches the brand name. Companies House also suggests looking at companies offering similar services as a way of identifying an appropriate SIC code. However, do not copy another company's SIC code blindly.

Two companies with similar websites can have materially different underlying activities. If you genuinely cannot determine the appropriate classification, Companies House's confirmation-statement guidance allows a brief description of the company's business activity where a code cannot be determined. For complicated or regulated businesses, professional accounting or legal advice may be appropriate.

How to Choose the Right SIC Code the Second Time

Use this simple framework.

1. Describe the activity

Complete this sentence: "My company primarily makes money by..." Be specific. "Technology" is too broad. "We develop subscription-based workflow software for recruitment agencies" is much more useful.

2. Identify the revenue activity

Ask what customers actually pay you for. Is it:

• selling products?
• manufacturing?
• software development?
• consultancy?
• professional services?
• property activity?
• advertising?
• education?
• transportation?

3. Check the official Companies House list

Use the condensed list rather than relying on a third-party directory. Companies House says only codes on its condensed list should be used when filing.

4. Add additional codes only when justified

If several genuine activities are important to the company, use the available additional codes.

5. Recheck the result

Ask:

"If someone saw this SIC code without visiting my website, would it give them a broadly accurate understanding of what my company does?"

If the answer is no, reconsider the selection.

A Practical Example: Choosing a SIC Code for a Digital Business

Imagine a startup called Global AI Skills Ltd. Its business activities are:

• teaching people how to use AI tools;
• providing digital-skills training;
• selling online training courses;
• offering corporate AI workshops.

The founder initially chooses a generic computer-services code simply because the company operates online. That may not accurately describe the company's primary activity. A better approach is to examine what customers actually pay for and compare those activities against the official SIC list.

If the company later expands into software development, it may need to review whether additional or different SIC codes are appropriate. The lesson is important: Choose the code based on the substance of the business, not simply the technology it uses.

How Often Should You Review Your SIC Code?

At minimum, review it as part of your annual confirmation-statement process. Companies House says every company must file a confirmation statement at least once every 12 months and check that its company information is correct. SIC code is specifically included among the information companies should review. But an annual review should not be the only trigger. Review your SIC code when:

• the company's main product changes;
• you enter a new industry;
• you stop providing a major service;
• the company becomes active after being dormant;
• your business model changes significantly;
• you discover the original code was inaccurate.

This is especially relevant to startups, where the business model can change substantially during the first few years.

FAQs

Can I change my SIC code after company formation?

Yes. Companies House allows companies to update their SIC code through the confirmation statement process. You can also file a confirmation statement early if you need to change the code before your next scheduled filing.

Do I need to close my company if I chose the wrong SIC code?

Usually, no. An incorrect SIC code does not normally require you to dissolve and recreate the company. You can correct the company's SIC information through the appropriate confirmation-statement process.

Can I change my SIC code immediately?

Yes. You do not necessarily have to wait for your next annual confirmation statement. Companies House allows an early confirmation statement where you need to update the SIC code sooner.

How many SIC codes can a UK company have?

A company can generally select up to four SIC codes where it carries out multiple activities. Each code should relate to a genuine business activity.

Does a SIC code have to exactly match everything my company does?

It should accurately reflect the company's economic activities, but it does not need to describe every minor task or future business idea. If the company carries out several significant activities, multiple SIC codes may be appropriate.

What happens if my company is trading but has a dormant SIC code?

You should correct it. Companies House has specifically identified the use of dormant or non-trading codes by active companies as a common discrepancy and says inaccurate SIC information may attract scrutiny.

Can I use a SIC code I found on another company's Companies House record?

You can use other companies as a reference when choosing a code, but do not copy a code without checking whether it actually describes your own activities. Companies House itself suggests looking at similar companies as one way to help identify an appropriate code.

Does my SIC code determine my Corporation Tax rate?

No. A SIC code classifies the company's economic activity; it does not itself determine the Corporation Tax rate. Tax treatment depends on the company's circumstances and applicable tax rules.

Does my SIC code give me permission to operate a regulated business?

No. A SIC code is a classification, not a licence or regulatory authorisation. Regulated businesses must separately comply with the requirements of the relevant regulator.

Conclusion

Choosing the wrong SIC code during company formation is usually a correctable administrative mistake, not a reason to start the incorporation process again. The important thing is to make sure the code accurately reflects what your company actually does. If you selected the wrong code during incorporation, you can normally update it through your confirmation statement. If you need to correct it before your next annual filing, Companies House allows you to file a confirmation statement early.

More importantly, treat your SIC code as an ongoing part of maintaining an accurate Companies House record. Companies House has strengthened its focus on the accuracy of information on the register and specifically advises companies to keep their SIC classifications aligned with their real activities.

For founders, especially global entrepreneurs establishing UK companies remotely, the best approach is straightforward: describe what the business actually does, use the official Companies House SIC list, select additional codes only where justified, and review the classification whenever the business materially changes. IncorpUK, a UK company formation and management platform for global founders, can be part of the broader process of establishing and managing a UK company. But whichever formation route you use, keeping your company's public information accurate remains an important responsibility of the business and its directors.