| 3E Security Limited | Bishops Stortford | 1992 |
| 3ELEMENT Covers Limited | Birmingham | 2022 |
| 3EMF Ltd | Sutton | 2026 |
| 3ET Manufacturing Limited | Markfield | 2022 |
| 3F Golf Ltd | Rochester | 2026 |
| 3F Industries Limited | Lincoln | 2015 |
| 3F Pellets Limited | London | 2015 |
| 3F Power Limited | Lincoln | 2015 |
| 3FLO-IMOTOTO Limited | Romford | 2024 |
| 3G Auto Limited | Burton-On-Trent | 2013 |
| 3G Joinery and Shopfitting Limited | Leeds | 2003 |
| 3G Rentals Limited | Leigh | 2024 |
| 3GR Limited | Bicester | 2000 |
| 3H Electronic Systems Limited | West Midlands | 2007 |
| 3H Joinery Limited | Swansea | 2026 |
| 3H Technologies Ltd | Bradford | 2018 |
| 3HARMONIES Ltd | Arminghall | 2021 |
| 3HD Engineering Limited | Cardiff | 2021 |
| 3I Optics Ltd | London | 2016 |
| 3J Services Limited | Walsall | 2018 |
| 3JB Ltd | Telford | 2026 |
| 3JC Enterprise Ltd | Cardiff | 2023 |
| 3JMIE Ltd | Wellingborough | 2024 |
| 3JT Ltd | London | 2019 |
| 3K Engineering Limited | Leicester | 2009 |
| 3K Home and Furniture Ltd | London | 2023 |
| 3LC Brewing Limited | Burntwood | 2025 |
| 3LG Print Ltd | Knowsley | 2009 |
| 3M Bakery Limited | Wellington | 2016 |
| 3M Drives & Controls Ltd | Stone | 2025 |
| 3M United Kingdom Public Limited Company | Berkshire | 1973 |
| 3M'S Carpentry Limited | Llanelli | 2023 |
| 3M1K Tailor Ltd | Cheadle | 2020 |
| 3MB Engineering Limited | Southampton | 2014 |
| 3MG Productions Ltd | London | 2025 |
| 3MINDS Ltd | West Midlands | 2003 |
| 3MM Bleed Ltd | Wooburn Green | 2019 |
| 3MOS Consulting Ltd | Milton Keynes | 2020 |
| 3MS Paints Ltd | Welwyn Garden City | 2017 |
| 3N Dark Composite Ltd | Cambridge | 2023 |
| 3O0 Studio Ltd | London | 2022 |
| 3P Atelier Ltd | London | 2026 |
| 3P Direct Limited | Mansfield | 2004 |
| 3P Innovation Limited | Warwick | 2006 |
| 3PD Limited | Huddersfield | 2026 |
| 3PV Ltd | London | 2019 |
| 3R Battery Solutions Ltd | Billericay | 2024 |
| 3R Design Ltd | Caernarfon | 2015 |
| 3R Energy Solutions Limited | Hawick | 2009 |
| 3R Print Ltd | London | 2025 |
| 3R W Design Ltd | Purfleet | 2014 |
| 3RACCESS Limited | Turriff | 2019 |
| 3RD Angle (U.K.) Ltd | Stourport On Severn | 1996 |
| 3RD Diadem Ltd. | London | 2011 |
| 3RD Down Collectables Ltd | London | 2021 |
| 3RD Hour Limited | Darlington | 2015 |
| 3RD Light Limited | Reading | 2004 |
| 3RD Rail Limited | Northampton | 2013 |
| 3RD Way Commonwealth Limited | Chorley | 2010 |
| 3RDGN Ltd | Stourport On Severn | 2001 |
| 3RIPLE G Ltd | Crawley | 2025 |
| 3ROTHER’S Meat Products Ltd | Luton | 2021 |
| 3RS Solihull Ltd | Solihull | 2022 |
| 3S Fabrications Limited | Evesham | 2025 |
| 3S Precision Co., Ltd | Kington | 2015 |
| 3S Projects Limited | Wolverhampton | 2011 |
| 3SB Limited | Norwich | 2014 |
| 3SHAPE UK Limited | Reading | 2021 |
| 3SIXTYWRAPS Ltd | Northampton | 2014 |
| 3T Additive Manufacturing Limited | Thatcham | 1997 |
| 3T Additive Manufacturing Polymers Ltd | Thatcham | 2020 |
| 3T Brewery Ltd | Rusper | 2025 |
| 3T Catering Group Ltd | Enfield | 2023 |
| 3T Coils Limited | Seaham Grange Industrial Estate | 2004 |
| 3THINK Ltd | Batley | 2004 |
| 3TL Group Ltd | Sandy | 2025 |
| 3TONE Arts Limited | Bristol | 2017 |
| 3VG Fixing Solutions Ltd | South Croydon | 2026 |
| 3VMEDS Bioscience Ltd | Manchester | 2024 |
| 3W Electronics Ltd | London | 2025 |
| 3WAYS Kitchens & Interiors Ltd | Whitby | 2021 |
| 3WEST Ltd | Alness | 2015 |
| 3WIND Ltd | Halesowen | 2021 |
| 3WM Signs Ltd | Nelson | 2015 |
| 3XR Studio Ltd | Flint | 2024 |
| 3YE Trading Co., Ltd | Cambridge | 2020 |
| 3ZEE Investment Limited | Northfleet, Gravesend | 2020 |
| 4 a Laugh Ltd | London | 2022 |
| 4 Absolute Holdings Ltd | Dunstable | 2013 |
| 4 Aluminium Ltd | Peterborough | 2015 |
| 4 Colour Digital Limited | Port Talbot | 2013 |
| 4 Concrete Ltd | Milton Keynes | 2016 |
| 4 Core Electrical Services Limited | Grimsby | 2018 |
| 4 Corners Marine Services Ltd | Cardiff | 2018 |
| 4 Corners Sign Print & Display Limited | Lisburn | 2015 |
| 4 Creative Solutions Limited | Kettering | 2013 |
| 4 Cyte UK Ltd | Dorking | 2018 |
| 4 Design Specialist Joinery Limited | Okehampton | 2020 |
| 4 Fabrications Limited | Birmingham | 2001 |
| 4 Family Records Ltd | Waltham Cross | 2020 |