| 3 Rivers Investments Limited | Borehamwood | 2005 |
| 3 Rock Productions Limited | London | 2018 |
| 3 S Security Ltd | Portsmouth | 2018 |
| 3 Security Ltd | Sutton | 2019 |
| 3 Shields Risk Solutions Ltd | London | 2026 |
| 3 Shires HR Limited | Crewe | 2013 |
| 3 Shires Marketing Limited | Knutsford | 2018 |
| 3 ST. Johns Road Limited | London | 2009 |
| 3 Star TV Systems Limited | Norwich | 2007 |
| 3 Stars PCO Limited | Ilford | 2023 |
| 3 Step IT Services Limited | London | 2021 |
| 3 Strides Cloud Consulting Limited | London | 2023 |
| 3 Style Plus Limited | London | 2006 |
| 3 Thames Road Limited | London | 2018 |
| 3 Tier Print Management Limited | Bradford | 2009 |
| 3 Tiers Creative Limited | Ellon | 2018 |
| 3 to 5 Club (Ireland) Ltd | Belfast | 2026 |
| 3 Way Cleaning Limited | Tilbury | 1997 |
| 3 Way Components Ltd. | Luton | 2014 |
| 3 Way Service Ltd | Hertford | 2003 |
| 3 Ways Wave Trading Limited | Warrington | 2025 |
| 3 Wimpole Street Limited | London | 2025 |
| 3 Winchester Road Freehold (Worthing) Limited | Worthing | 2003 |
| 3 Wizards Entertainment Limited | St. Leonards-On-Sea | 2019 |
| 3 Word Group Limited | Petworth | 2025 |
| 3-7 Byfleet TC Manco Limited | Chertsey | 2022 |
| 3-GUN Nation UK Ltd | Cadishead | 2017 |
| 3-WAVE Consultancy Ltd | Finchley | 2010 |
| 3-WISE Limited | Hook | 2002 |
| 3.18 Ltd | Luton | 2017 |
| 30 Battenhall RTM Company Limited | Worcester | 2021 |
| 30 Cissbury Road Hove Limited | Brighton And Hove | 2007 |
| 30 Clarendon Road Limited | London | 2018 |
| 30 Dancer Road Management Company Limited | Hampton Hill | 2008 |
| 30 Degrees Limited | Leighton Buzzard | 2018 |
| 30 Eversfield Place (Management Company) Limited | | 2005 |
| 30 Goss Lane Management Limited | Bristol | 2014 |
| 30 Goss Lane Nailsea Ltd | Bristol | 2018 |
| 30 Grays Inn Limited | London | 2014 |
| 30 GS Management Services Limited | London | 2023 |
| 30 Lytton Grove Limited | | 2000 |
| 30 Old Church Street (Freehold) Limited | Welwyn Garden City | 2021 |
| 30 Pier Street Ventnor Limited | Chichester | 2011 |
| 30 West Aviation and Human Factors Consultants Ltd | Newark Nottinghamshire | 2017 |
| 30 Willoughby Road Limited | London | 1995 |
| 300 Guards Limited | London | 2021 |
| 300 North Consulting Ltd | Leeds | 2015 |
| 300 Sales Limited | Swindon | 2004 |
| 3007 Limited | Liverpool | 2021 |
| 301 Design Limited | South Croydon | 1997 |
| 3011MAPLESIGN Ltd | Heskin | 2006 |
| 3032 Powney Road Limited | London | 1999 |
| 303EVENT Ltd | London | 2016 |
| 305 Digital Asset Management Ltd | London | 2023 |
| 308 Recruitment Ltd | Woking | 2025 |
| 30:30 Recordings Ltd | Twickenham | 2006 |
| 30CRFH Ltd | London | 2021 |
| 30SIX Agency Limited | Hollinwood | 2020 |
| 30THOUSANDFEET Limited | Droitwich | 2019 |
| 30X30 United Kingdom CIC | Beaminster | 2025 |
| 30XAG Ltd | Birmingham | 2026 |
| 31 & 32 Manchester Street Limited | London | 2019 |
| 31 Albert Bridge Road Limited | London | 2013 |
| 31 Branksome Road Limited | London | 2007 |
| 31 Courtyard Ltd | Hamilton | 2017 |
| 31 Eversfield Place (Management Company) Limited | | 2005 |
| 31 Glengall Road London NW6 (Management) Limited | | 1991 |
| 31 Gloucester Avenue Limited | London | 2009 |
| 31 Irving Road Management Company Limited | London | 2001 |
| 31 Kimberley Road Management Limited | Bristol | 2004 |
| 31 Media Limited | Norwich | 2007 |
| 31 Moring Road Limited | London | 2001 |
| 31 Parkwood Road Freehold Limited | Bournemouth | 2000 |
| 31 ST Lukes Road Management Limited | Macclesfield | 2000 |
| 31 Weyside Road Management Company Ltd | Guildford | 2015 |
| 31 Wood Street (Swindon) Management Company Ltd | Swindon | 2003 |
| 31-36 Moor Gate RTM Company Limited | Bristol | 2011 |
| 31/33, Crescent Road (Luton) Residents Association Limited | Luton | 1970 |
| 311 Window Film & Manifestation Limited | Windsor | 2016 |
| 3110 Limited | Penrith | 2010 |
| 31105 Ltd | Haywards Heath | 2025 |
| 312 Stakeholders Limited | Bristol | 2020 |
| 313 Car Hire Ltd | Rainham | 2024 |
| 313 Motors Ltd | Liverpool | 2023 |
| 313 Recruiters Ltd | Watford | 2022 |
| 313 Resourcing Ltd | High Wycombe | 2024 |
| 314810 Ltd | Southport | 2021 |
| 315 Connect Ltd | London | 2026 |
| 3156 Boxing Limited | Newcastle Upon Tyne | 2026 |
| 317 Richmond Road Management Limited | Middlesex | 1990 |
| 317 Sourcing Ltd | London | 2026 |
| 318 to 326 Hornsey Road Ltd | Barnet | 2019 |
| 3191 Limited | Rochdale | 2011 |
| 31ST Estates Ltd | London | 2024 |
| 32 and Counting Limited | Birmingham | 2026 |
| 32 Anglesea Limited | Ipswich | 2017 |
| 32 Arnolds Way Management Limited | Oxford | 2013 |
| 32 Church Street RTM Company Ltd | Wetherby | 2016 |
| 32 Comeragh Road (Freehold) Limited | | 1997 |
| 32 Dulwich Road Limited | London | 2005 |