| 3D Operations Limited | Gateshead | 2020 |
| 3D Parking Ltd | London | 2010 |
| 3D Personnel (NI) Limited | Belfast | 2015 |
| 3D Personnel Group Limited | Southampton | 2013 |
| 3D Personnel Limited | Edinburgh | 2007 |
| 3D Planning Limited | Peterborough | 2007 |
| 3D Plant and Machinery Limited | Birmingham | 1993 |
| 3D Plant Hire Ltd | Stockton On Tees | 2026 |
| 3D Productions Ltd | Leeds | 2000 |
| 3D Protection Ltd | Surtees Business Park | 2013 |
| 3D Recruit Limited | Battle | 2002 |
| 3D Scantech Limited | Coventry | 2006 |
| 3D Security Ltd | Fareham | 2007 |
| 3D Security Systems Limited | Swanage | 2018 |
| 3D Site Engineers Limited | Edwalton | 2014 |
| 3D Storage Systems (UK) Limited | Wakefield | 2006 |
| 3D Strategy Limited | Huddersfield | 2010 |
| 3D'S Cleaning Solutions Ltd | Birmingham | 2026 |
| 3D'S Global Concept Limited | Wellingborough | 2014 |
| 3D2D Events England Limited | Gateshead | 2019 |
| 3D2D Events Limited | Dalkeith | 2024 |
| 3DC Learning Limited | Croydon | 2019 |
| 3DCLEVER Ltd | Whitchurch | 2019 |
| 3DDC Holdings Ltd | North Crawley | 2010 |
| 3DDC Limited | North Crawley | 2007 |
| 3DEGREES Europe Ltd | London | 2019 |
| 3DEVICES Packaging Solutions Ltd | Bolton | 2025 |
| 3DG Security Ltd | Ellesmere Port | 2024 |
| 3DI Imagery to Mapping Limited | Hove | 2007 |
| 3DMA Ltd | Halifax | 2013 |
| 3DOM Rental Ltd | Leighton Buzzard | 2022 |
| 3DUSERNET Ltd | London | 2017 |
| 3E Development Limited | Edinburgh | 1995 |
| 3E Global Ltd | Sleaford | 2014 |
| 3E Search Limited | London | 2021 |
| 3E Security+ Limited | Manchester | 2023 |
| 3EA Consultancy Limited | Sale | 2020 |
| 3ECRUIT Ltd | Wrexham | 2008 |
| 3EDGE Limited | Glasgow | 2014 |
| 3FLO Ltd | St. Albans | 2011 |
| 3FOR Limited | Pontefract | 2014 |
| 3FS Aviation Limited | Chichester | 2007 |
| 3FUND PVT Ltd | Plymouth | 2018 |
| 3G Contract Cleaning Limited | Peacehaven | 2013 |
| 3G International Limited | Bognor Regis | 2003 |
| 3G Projects Ltd | Bristol | 2007 |
| 3G Travels Ltd | London | 2017 |
| 3G Wave Investments Ltd | Newbury | 2008 |
| 3GATES Property Maintenance Limited | Cleckheaton | 2008 |
| 3GEN Fire Ltd | Edenbridge | 2024 |
| 3GF Limited | Horsham | 2012 |
| 3GOR Limited | Kilmarnock | 2024 |
| 3GRCOMM Limited | Hereford | 2000 |
| 3GS (UK) Limited | Flintshire | 2012 |
| 3GWM Ltd | Pudsey | 2019 |
| 3H Capital Ltd | Norwich | 2016 |
| 3H Foundry Limited | London | 2025 |
| 3H Site Protection (UK) Ltd | London | 2019 |
| 3HA Limited | Colchester | 2013 |
| 3HG Services Ltd | London | 2025 |
| 3HIRTY6IX Ltd | London | 2019 |
| 3HM Associates Ltd | Southall | 2023 |
| 3I GP 2004 Limited | Glasgow | 2004 |
| 3I Music Limited | London | 2012 |
| 3I Strategies Ltd | Reading | 2025 |
| 3IDOG Limited | Truro | 2009 |
| 3ITC Limited | Swaffham | 2020 |
| 3J Finance Limited | London | 2008 |
| 3J Private Hire Ltd | Edinburgh | 2023 |
| 3JANE Limited | London | 2023 |
| 3JN Ltd | Stroud | 2008 |
| 3JRM Ltd | Strabane | 2018 |
| 3JSS Limited | Droitwich | 2017 |
| 3J’S Landscaping Ltd | Radstock | 2023 |
| 3K Services Limited | Keighley | 2017 |
| 3K Solutions Limited | Bradford | 2010 |
| 3K'S Trading Ltd | Congleton | 1984 |
| 3KC (Corporate Services) Limited | London | 2026 |
| 3KITES Consulting Ltd | Woking | 2005 |
| 3KS GE Specialists Limited | Letchworth Garden City | 2010 |
| 3L Consulting & Coaching Ltd | Loughborough | 2017 |
| 3L Security Ltd | Dover | 2016 |
| 3LA.COM Limited | London | 2009 |
| 3LANCE Education Ltd | Wembley | 2021 |
| 3LANCE Limited | Wembley | 2014 |
| 3LANCE Recruitment Solutions Ltd | Wembley | 2021 |
| 3LEAF Clover Ltd | London | 2020 |
| 3LINECARRENTALS Ltd | Leeds | 2025 |
| 3LINKS Consultancy Limited | Tadley | 2009 |
| 3LITE Protection Services Ltd | London | 2025 |
| 3M Air Ltd | Milford Haven | 2022 |
| 3M Autozone Ltd | London | 2026 |
| 3M Care Ltd | Hounslow | 2016 |
| 3M Enterprise HQ Ltd | Birmingham | 2026 |
| 3M Hospitality Limited | London | 2012 |
| 3M Installations Ltd | Cardiff | 2017 |
| 3M Property Sourcing Limited | Birmingham | 2023 |
| 3M Resourcing Ltd | Lutterworth | 2023 |
| 3M&I Ltd | Ormskirk | 2025 |
| 3MA Limited | Kington | 2012 |