| 3 Muskateers Ltd | Coventry | 2016 |
| 3 NDT Ltd | Darlington | 2020 |
| 3 on the DOT Limited | Horley | 2012 |
| 3 Over 5 Design Limited | Maidstone | 2026 |
| 3 Peaks Consulting Limited | Lancaster | 2014 |
| 3 Peaks Digital Limited | Driffield | 2021 |
| 3 Peaks Recruitment Limited | Lisburn | 2026 |
| 3 PG & D Limited | Bathgate | 2016 |
| 3 Phase Creative Limited | Kingston Upon Thames | 2023 |
| 3 Point Management Systems Ltd | Llandudno | 2021 |
| 3 Point Surveys Limited | Cardiff | 2011 |
| 3 Ravens Agency Ltd | Sheffield | 2024 |
| 3 Realms of the Digital Frontier Limited | Pinner | 2019 |
| 3 Reasons Limited | London | 2014 |
| 3 Riviera Terrace Management Company Limited | Dawlish | 2000 |
| 3 Russell Street (Bath) Limited | Bath | 1978 |
| 3 Second Rule Ltd | Mildenhall | 2025 |
| 3 Shires Drone Surveys & Aerial Pictures Ltd | Malvern | 2019 |
| 3 Sigma Capital Ltd | London | 2021 |
| 3 Sigma Limited | Westhill | 1999 |
| 3 Sixty Accountants Ltd | Peterborough | 2011 |
| 3 Sixty Market Research Limited | Hungerford | 2014 |
| 3 Spires Solicitors Limited | Birmingham | 2007 |
| 3 Spires Testing Ltd | Coventry | 2012 |
| 3 Stories High Limited | London | 2009 |
| 3 Systems Lean Ltd. | Doncaster | 2014 |
| 3 Things Consulting Ltd | Bolton | 2018 |
| 3 Tier Solutions Limited | Leigh-On-Sea | 2016 |
| 3 to 48 Ltd | Whitehills Business Park | 2019 |
| 3 Valued Things Ltd | London | 2021 |
| 3 W Associates (UK) Ltd | Portsmouth | 2016 |
| 3 Way WIN Limited | West Horsley | 2015 |
| 3 Web Digital Ltd | London | 2023 |
| 3 With 8 Limited | Macclesfield | 2022 |
| 3 X 1 Digital Limited | Falkirk | 2015 |
| 3&5 Holding Ltd | Edgware | 2024 |
| 3, South Hill Park Gardens Limited | London | 1979 |
| 3-10 Grosvenor Crescent Management Limited | London | 2010 |
| 3-16HOLDINGS Limited | London | 2016 |
| 3-5 Borough Street Management Company Limited | Derby | 2013 |
| 3-D Architecture Limited | Uckfield | 2004 |
| 3-D Business Services Limited | Welling | 2015 |
| 3-EIGHT Communications Ltd | Ashover | 2017 |
| 3-FOURTEEN Design Limited | Kings Langley | 2024 |
| 3-MOTION Ltd | Leicester | 2011 |
| 3-SAINTS Energy Ltd | Bangor | 2019 |
| 3-SCI Ltd | Farnborough | 2013 |
| 3-SPHERE London Ltd | London | 2014 |
| 3-WAVE Services Limited | Bristol | 2003 |
| 3.1 Solutions Ltd | Shrewsbury | 2025 |
| 3.1415 Limited | London | 2023 |
| 3.1416 Limited | Coalville | 2021 |
| 3.NG Limited | London | 2025 |
| 3/4 South Cliff Management Company Limited | Sunderland | 1988 |
| 30 Alhambra Road Limited | Hants | 2005 |
| 30 Archfield Road Bristol (Management) Limited | Bristol | 1986 |
| 30 Barrels Ltd | London | 2021 |
| 30 Bracknell Gardens Freehold Limited | Wimborne | 2009 |
| 30 Carlingford Road Limited | London | 1978 |
| 30 Clicks Ltd | London | 2025 |
| 30 Combe Park Bath (Management) Limited | Bath | 1987 |
| 30 Day Architecture Limited | London | 2024 |
| 30 Day Extensions Consultancy Ltd | Wimbledon | 2024 |
| 30 Degrees North Ltd | London | 2013 |
| 30 Gladstone Road Management Co. Limited | Eastleigh | 2004 |
| 30 Hour Days Limited | York | 2015 |
| 30 Knowle Road Flat Management Limited | Bristol | 1993 |
| 30 Mount Ephraim Road Limited | | 2003 |
| 30 Palace Court Management Limited | London | 1995 |
| 30 ST Michael's Place Brighton Limited | Southwick | 2005 |
| 30 ST. Margaret's Street (Bradford on Avon) Limited | Bradford-On-Avon | 2001 |
| 30,000 Days Limited | London | 2019 |
| 300 Marketing & Communications Limited | Enfield | 2018 |
| 300 Risk Limited | Burgess Hill | 2026 |
| 300.LONDON Limited | Southampton | 2020 |
| 300300 Limited | Haydock | 2020 |
| 30042509 Ltd | Belfast | 2023 |
| 301 Studio Limited | Brighton | 2025 |
| 301 Taxis Ltd. | Livingston | 2019 |
| 301123 Ltd | Bedford | 2026 |
| 302 MD Ltd | London | 2024 |
| 303 Creative Ltd | Weston-Super-Mare | 2021 |
| 303 Delivery Ltd | Twickenham | 2026 |
| 303 Global Ltd | London | 2026 |
| 303 Group Ltd | Blackpool | 2023 |
| 303 Partners Ltd | London | 2014 |
| 304 Group Ltd | London | 2021 |
| 305 Live Ltd | Stockport | 2019 |
| 306 PSI Ltd | Caterham | 2026 |
| 3060 Marketing Ltd | Stirling | 2024 |
| 30A Architecture Ltd | London | 2018 |
| 30AD Limited | Glasgow | 2026 |
| 30W Ltd | Ruislip, | 2026 |
| 30WEST Consultancy Limited | Ammanford | 2020 |
| 31 Armfield Road (Enfield) Management Company Limited | Enfield | 2003 |
| 31 Burnaby Road Management Ltd | Bournemouth | 2021 |
| 31 Canfield Gardens Limited | | 1994 |
| 31 Cresswell Road Limited | Twickenham | 2014 |
| 31 Culverden Park Road Management Company Limited | Tunbridge Wells | 1984 |
| 31 December Consulting Private Limited | Rayleigh | 2018 |