UK SIC Code Lookup: How to Find the Right Codes for B2B Prospecting

Every UK limited company picks one to five SIC codes when it incorporates. They're the single most powerful filter for B2B prospecting on Companies House data, but only if you know how to use them properly.

This guide explains what SIC codes are, how to look them up, and the common mistakes that turn a precise filter into a noisy one.

What a SIC code actually is

SIC stands for Standard Industrial Classification. The current UK version is the SIC 2007 revision (the same revision used since 2008, there's been talk of an update but as of 2026, no new version has been published). It contains around 730 five-digit codes grouped into 21 lettered sections.

The codes are hierarchical:

• Section letter (e.g. C = Manufacturing)
• 2-digit division (e.g. 25 = Manufacture of fabricated metal products)
• 3-digit group (e.g. 256 = Treatment + coating of metals)
• 4-digit class (e.g. 2562 = Machining)
• 5-digit subclass (e.g. 25620 = Machining)

For UK Companies House filings, only the 5-digit codes are valid. Anything you see on a Companies House profile is a 5-digit SIC.

Where to look codes up

Three official sources, ordered by usefulness:

1. The Companies House SIC code list, the canonical UK list. Go to https://resources.companieshouse.gov.uk/sic/. It's a flat HTML page; ctrl-F is your friend. 2. The ONS SIC 2007 explanatory notes, when a code's name is ambiguous, the ONS PDF has the full explanatory note describing what's in and out. Worth keeping bookmarked. 3. The Leadistry SIC search, built into the search builder. Type a keyword and get every code that matches. Free even on the trial tier.

Why one code is rarely enough

The trick to using SIC codes for prospecting is that they are *self-declared*. A new founder picking codes during incorporation will often choose whatever sounds closest, not what is technically correct.

The result: a "plumber" might file as 43221 (the correct plumbing code), or 43220, 43210, 43222, 43229, 43320, or 43990 depending on what they read first. To target plumbing prospects reliably, you need a cluster of codes, not a single one.

A defensible plumbing prospect list looks like:

• 43210, Electrical installation
• 43221, Plumbing, heat and air conditioning installation
• 43222, Other heat installation
• 43229, Other plumbing-related installation activities

Cast wide on related codes, then sub-filter on company name, region, or website signals.

The 5 most-misclassified UK SIC codes

After indexing 5M+ UK active companies, certain codes show up repeatedly in places they don't belong:

1. 70229, "Other management consultancy". Used as a default by founders who don't know what else to pick. About 15% of "consultancy" filings are doing something else entirely. Pair with the company name or website to filter out the noise. 2. 74909, "Other professional, scientific, technical activities n.e.c.". The classic "I don't know what to file" code. Sometimes legitimately niche, more often a placeholder. 3. 96090, "Other service activities n.e.c.". Similar, a catch-all that contains everything from spiritual healers to dog walkers. 4. 62012, "Business and domestic software development". Often filed by IT consultancies that aren't really software developers. Cross-check against the company website to confirm. 5. 47910, "Retail sale via mail order houses or via the internet". Used by both serious e-commerce and one-product hobby sellers. Combine with company age + accounting category for sharper signal.

SIC vs UK NACE / EU classification

For cross-border work, UK SIC 2007 is derived from EU NACE Rev. 2 but not identical. The 4-digit codes match; the 5-digit subclasses are UK-specific. If you're targeting both UK and EU companies, you can filter UK SIC + map back to NACE for the rest.

Highest-value SIC codes for B2B SaaS in 2026

Based on conversion data from Leadistry's own pipeline (your mileage will vary):

• 62012 (software development), highest digital-tooling adoption
• 70229 (management consultancy), sole-director ICP, fast decisions
• 69201 (accounting + tax), software-buying culture, lots of SME inbound
• 41100 (development of building projects), high-volume + low-tooling sector, lots of opportunity
• 47910 (mail order / e-commerce), naturally digital + tool-heavy buyers

Combining SIC with other filters

SIC alone produces too-large lists for most use cases. Combine it with:

• Postcode prefix for territory
• Incorporation date for age cohort
• Accounting category as a headcount proxy
• Director name not in suppression list for compliance

A typical Leadistry prospect list looks like *"SIC 70229 + LS postcode + incorporated 2–7 years ago + active company status"*, that's specific enough to be useful, broad enough to surface real volume.

Common mistakes

1. Picking only one SIC code. Founders mis-classify. Cast wider. 2. Treating SIC as ground truth. It's self-declared, sometimes wrong. Use website / LinkedIn signals to validate. 3. Ignoring the "n.e.c." codes. They contain a lot of noise but also a lot of legitimate niche businesses you'd otherwise miss. 4. Over-filtering on accounting category. Micro / small / medium boundaries are wide; don't trust them for sharp targeting. 5. Forgetting cross-border firms. UK firms with EU operations sometimes file niche SIC codes that don't map to UK norms.

Bottom line

UK SIC codes are the most powerful filter Companies House gives you, but they're noisy. Use them in clusters, validate against secondary signals, and don't forget the misclassification problem.

Try the Leadistry SIC search free, 6 trial leads, no card required.