UK SIC 2007 · 43999
Other specialised construction activities n.e.c.
Other specialised construction activities n.e.c. is UK SIC code 43999, part of division 43 (Specialised construction activities) in the SIC 2007 classification. As of the July 2026 Companies House register, 62,538 active UK companies list 43999 among their SIC codes, and 47,685 list it as their first code. That makes it the most used code in its division.
As of the July 2026 Companies House register, 62,538 active UK companies list 43999 among their SIC codes (47,685 as their first code).
Companies House data refreshed daily. Page reviewed July 2026.
Division 43: Specialised construction activities
Division 43 is the trades division, and one of the largest classifications on the UK register. Electricians register under 43210, plumbing and heating engineers under 43220, roofers under 43910, and plasterers, painters, glaziers, floorers and scaffolders each under their own code. Two broad codes swell the numbers further: 43999 for specialised activities not elsewhere classified and 43390 for other building completion and finishing, both catch-alls that absorb general trades and multi-skilled firms. Most companies are small, many being a single tradesperson who incorporated for contracting or tax reasons.
The trades are relentlessly prospected because their needs are predictable and recurring: public liability insurance, accountancy for CIS refunds and limited company compliance, van leasing, tool suppliers and merchants offering trade credit. Lead generation and website services target the no-website majority, since a tradesperson visible on the register but invisible on search is losing local work. New incorporations are the standout signal, usually marking the jump from sole trader to limited company when insurance, banking and bookkeeping all get chosen within weeks. Heating firms under 43220 also draw sellers of renewables kit, especially heat pump distributors.
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About SIC 43999
How many UK companies use SIC code 43999?
62,538 active UK companies include 43999 (Other specialised construction activities n.e.c.) among their up-to-four registered SIC codes, of which 47,685 list it first. Figures are from the July 2026 Companies House register snapshot, counting active companies only.
Should a multi-trade builder use 43999 or a specific trade code?
If one trade produces most of your income, use its specific code, such as 43210 for electrical or 43220 for plumbing and heating, because specific codes read more credibly to insurers and merchants. Genuinely multi-skilled firms use 43999 or 43390, or list up to four codes covering their main trades. The selection is yours; Companies House records it without judgement and it can change on any confirmation statement.
Does my SIC code need to match my trade qualifications or scheme memberships?
No formal link exists. Gas Safe registration, NICEIC enrolment and similar scheme memberships are checked on their own registers, not against Companies House. Choosing the code matching your trade is still worthwhile, because prospective customers, insurers and finance providers do look at it, and a mismatch invites questions. If the business changes direction, update the code via the CS01 confirmation statement at your next filing.
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