SIC codes explained: how to use them to find B2B prospects.

If you want a list of every plumbing firm, architect or IT consultancy in your area, you need a way to filter UK companies by industry. That's what SIC codes are for. They're free, they're on every company's public record and they cover every limited company in the country.

They're also imperfect. This guide explains what SIC codes are, where to find them, how to use them for prospecting and how to work around their weaknesses.

What is a SIC code?

SIC stands for Standard Industrial Classification. It's a system for classifying businesses by the type of economic activity they carry out. In the UK, Companies House uses the UK SIC 2007 classification, in which each detailed activity has a five-digit code.

The codes are hierarchical. The first two digits give a broad division, and later digits narrow it down. For example, codes starting with 43 cover specialised construction activities, and 43220 is plumbing, heat and air-conditioning installation within that group. That structure is handy for prospecting: you can target a precise activity, or a whole family of related ones.

Where to find a company's SIC codes

Every company's codes appear under Nature of business on its overview page on Companies House. They're also included in Companies House's free API and bulk data, so you can filter large numbers of companies by code. Our guide to using Companies House data for lead generation covers those options.

Key facts:

• A company chooses its own codes when it's incorporated.
• A company can list up to four SIC codes.
• Companies confirm or update their codes in their annual confirmation statement.

Common SIC codes for B2B prospecting

Here are some codes for industries that often buy from other businesses. Use the full list on GOV.UK to find the codes for your own target market.

Two codes to treat with care: 99999 means a dormant company, which you'll almost always want to exclude, and 82990 (other business support service activities not elsewhere classified) is a broad catch-all that covers very different businesses.

The limits of SIC codes

SIC codes are a filter, not a guarantee. Know their weaknesses before you rely on them.

• They're self-chosen. Companies pick their own codes, and nobody checks them. Some choose a code that's close enough; some choose one at random from a formation agent's form.
• They go out of date. A business that started as a web designer and became a marketing agency may never have changed its code.
• Some are very broad. Catch-all "not elsewhere classified" codes group together businesses with little in common.
• Similar businesses use different codes. A plumbing and heating firm might use 43220, a general building code or both. Search for all the plausible codes, not just the obvious one.
• The classification itself changes. Industry classifications are revised from time to time, so check which version a data source is using.

Combine SIC codes with other filters

An industry filter on its own gives you a long list. Combine it with the other data on the register to get a short, useful one.

1. Company status: keep active companies only.
2. Location: filter by registered office postcode, within a radius or region. Remember that some companies use their accountant's address as their registered office.
3. Age: use the incorporation date to skip businesses that are too new to buy.
4. Size: the type of accounts a company files gives a rough sense of its size.
5. Directors: check who runs the business, so your email reaches the person who can say yes. See how to find a director's email address.

For example, "active companies with SIC code 43220, registered within 25 miles of Canterbury, incorporated more than five years ago" turns hundreds of thousands of companies into a list you can work through personally.

Choosing the right codes for your market

Picking codes is easier if you work backwards from customers you already have.

1. Look up your best customers. Search for your five or ten favourite customers on Companies House and note the codes they've chosen. You'll often find they use more variety than you expected.
2. Browse the neighbouring codes. Because the classification is hierarchical, codes that share their first few digits cover related activities. Read through them and add any that describe businesses you could serve.
3. Separate core codes from possible ones. Core codes almost always describe your customers. Possible codes sometimes do. Treat results from possible codes as a list to check, not a list to email straight away.
4. Exclude what doesn't fit. Remove dormant companies, holding companies and any activities you can't serve, even if they're close to your market.
5. Review after a few weeks. Look at which codes produced replies and customers, and adjust your list.

If your customers span several industries, as they often do for agencies, recruiters and software companies, it's usually better to run separate searches for each industry. That way you can tailor your message to each one rather than writing a generic email for everyone. A message that mentions the recipient's own industry is far more likely to get a reply.

A worked example

Say you supply parts to heating engineers in Kent.

1. Start with 43220 (plumbing, heat and air-conditioning installation).
2. Add related codes your customers might use, such as general building codes, then check those results more carefully.
3. Filter to active companies with a registered office within your delivery area.
4. Remove companies incorporated in the last year.
5. Check each remaining company's website to confirm what they do and where they trade.
6. Find the director and a verified email address, then write to them personally.

Letting software do the filtering

Pucky lets you describe your ideal customer the way you'd explain it to a colleague, such as "plumbing and heating firms within 25 miles of Canterbury", and turns it into a search across every company on the UK register, filtered by industry, area, age and size. It then finds each business's website and its directors. See UK company search.

Frequently asked questions