| 3S Architects Ltd | Richmond | 2019 |
| 3S Business Solution Ltd | Newcastle | 2021 |
| 3S Commercial Consulting Limited | Darlington | 2016 |
| 3S Commercial Ltd | Guildford | 2011 |
| 3S Consultancy Ltd | Rugby | 2025 |
| 3S Consulting Limited | London | 2022 |
| 3S Experience Ltd | London | 2025 |
| 3S Interiors Ltd | Richmond | 2010 |
| 3S Investments Ltd | Peacehaven | 2016 |
| 3S Knowledge Limited | Warwick | 2018 |
| 3S Legal Ltd | London | 2025 |
| 3S Manufacturing Limited | Derby | 2009 |
| 3S Mortgages Ltd | Wolverhampton | 2007 |
| 3S Northumbria Ltd | Alnwick | 2023 |
| 3S Power Ltd | Waltham Cross | 2026 |
| 3S Sogny Site Solutions Ltd | Ilford | 2024 |
| 3S Trading Consultancy Limited | Newcastle | 2023 |
| 3S-SYSTEMS Limited | Sandy | 2004 |
| 3SD Research Ltd | Falmouth | 2018 |
| 3SD Ventures Ltd | Hassocks | 2018 |
| 3SE+ Services Limited | Bristol | 2026 |
| 3SEC Accounts Ltd | Paisley | 2021 |
| 3SECOND Ltd | Harrow | 2025 |
| 3SF Limited | Brighouse | 2020 |
| 3SFIRE Community Interest Company | Eastleigh | 2013 |
| 3SG Ltd | London | 2017 |
| 3SGROUP Limited | Oakhampton | 2004 |
| 3SI Consultants Ltd | Chislehurst | 2023 |
| 3SIX5 Digital Enterprises Ltd. | London | 2018 |
| 3SIXFIVE Pro Limited | Cardiff | 2019 |
| 3SIXTY Consultancy Ltd | Epsom | 2024 |
| 3SIXTY Creative Marketing Solutions Ltd | Birmingham | 2011 |
| 3SIXTY Creative Solutions Ltd | Brierley Hill | 2024 |
| 3SIXTY Estate Planning Limited | Sheffield | 2020 |
| 3SIXTY Estimating Services Ltd | Kingswinford | 2010 |
| 3SIXTY Event Consulting Limited | Chinnor | 2017 |
| 3SIXTY Founders Limited | London | 2019 |
| 3SIXTY Health and Safety Ltd. | Bicester | 2014 |
| 3SIXTY IQ Limited | Swindon | 2024 |
| 3SIXTY Limited | St. Albans | 2025 |
| 3SIXTY Luxury Ltd | Henley On Thames | 2014 |
| 3SIXTY Outsourcing Limited | Northampton | 2021 |
| 3SIXTY Strategic Advisors Ltd. | London | 2018 |
| 3SIXTY Tour Management Ltd | Newcastle Upon Tyne | 2020 |
| 3SIXTY Visual Marketing Limited | St. Albans | 2019 |
| 3SIXTYMEASUREMENT Limited | Teddington | 2007 |
| 3SL Consulting Ltd | Heywood | 2014 |
| 3SL Limited | London | 2013 |
| 3SL Overseas Limited | Alderley Edge | 1984 |
| 3SPHERES UK Ltd | Wellington | 2009 |
| 3SPR Management Services Ltd | Birmingham | 2015 |
| 3SR Consulting Ltd | Houghton Le Spring | 2026 |
| 3SR Ltd | Macclesfield | 2010 |
| 3ST Consulting Limited | Maidenhead | 2006 |
| 3STAGE Ltd | London | 2020 |
| 3STIM8 Ltd | Portsmouth | 2022 |
| 3STONELAKE Ltd | London | 2024 |
| 3SUN Group Limited | London | 2008 |
| 3SUN Inspection Services Limited | London | 2011 |
| 3T Accounting and Consultancy Services Limited | Glasgow | 2020 |
| 3T Consultancy Limited | Ashbourne | 2022 |
| 3T Professional Services Limited | Stoke-On-Trent | 2005 |
| 3T Tax Limited | Chesham | 2008 |
| 3T Technologies Limited | Hertford | 2004 |
| 3T'S Consulting Ltd | Leeds | 2025 |
| 3TAB Holdings Limited | Diss | 2017 |
| 3TAU Limited | Worthing | 2003 |
| 3TAX Solutions Ltd | Littleborough | 2025 |
| 3TC Limited | London | 2023 |
| 3THINKIN Ltd | Banstead | 2010 |
| 3THINKRS Ltd | London | 2020 |
| 3THOS Ltd | London | 2022 |
| 3TJ Global Limited | Bromley | 2004 |
| 3TKN Limited | Malvern | 2011 |
| 3TM&F Limited | Dagenham | 2016 |
| 3TOOL.AI Ltd | Cardiff | 2025 |
| 3TS Advisory Ltd | Sevenoaks | 2026 |
| 3TS Top Tool Trading Company Limited | West Midlands | 1999 |
| 3TTECHGROUP Ltd | Accrington | 2023 |
| 3U Holdings Ltd | Dewsbury | 2025 |
| 3U Summer Co., Ltd | London | 2015 |
| 3UPNET Limited | Gillingham | 2005 |
| 3V Interim Finance Limited | Whitehills Business Park | 2016 |
| 3V Legal Ltd | Liverpool | 2021 |
| 3V Natural Foods Limited | Gloucester | 2006 |
| 3V Solutions Ltd | Carshalton | 2019 |
| 3V3 Labs Ltd | London | 2025 |
| 3VI Limited | London | 2008 |
| 3VIEWSKY Limited | Aldershot | 2024 |
| 3VISION Limited | Bath | 2003 |
| 3VISION Media Ltd | London | 2021 |
| 3VOLUTION Limited | Ilkley | 2023 |
| 3VQ Limited | Witney | 2022 |
| 3VS UK Limited | Harrow | 2004 |
| 3W Architecture Limited | London | 1995 |
| 3W Consulting Ltd | Liverpool | 2012 |
| 3W Growth Limited | Nottingham | 2016 |
| 3WAYSUPVENTOUX Limited | Saxmundham | 2024 |
| 3WH Limited | Praze | 2022 |
| 3WHYSE Ltd | Lytham St. Annes | 2022 |