| BUDD5 Ltd | Financial services | 2022 |
| Budget Contract Distribution Ltd | Transport & logistics | 2001 |
| Budget Rubbish & Maintenance Limited | Professional & scientific | 2015 |
| Buff Games Ltd | Information & communication | 2016 |
| Buffalo Fabrication Ltd | Manufacturing | 2021 |
| Buffers Residential Cleaning Ltd | Administrative & support | 2019 |
| Buffers Service Group Ltd | Professional & scientific | 2019 |
| Bugnut Limited | Wholesale & retail | 2022 |
| Build-Pay Ltd | Information & communication | 2026 |
| Building Safety 4 Ltd | Professional & scientific | 2024 |
| Building STG Limited | Construction | 2017 |
| Building Works Matters Ltd | Construction | 2024 |
| Built Consulting Ltd | Financial services | 2024 |
| Built Well Home and Garden Ltd | Administrative & support | 2025 |
| Bukunmotayo Studios Ltd | Wholesale & retail | 2025 |
| Bulldog Properties Gunwharf Quays Ltd | Real estate | 2024 |
| Bulwark Enterprises Limited | Professional & scientific | 2012 |
| Bunked Investments Ltd | Real estate | 2020 |
| Bunked Ltd | Real estate | 2018 |
| Bunn Abbott Consulting Limited | Administrative & support | 2021 |
| Burak Kebab Ltd | Hospitality | 2025 |
| Burdon Property Investments Ltd | Real estate | 2017 |
| Burdon's Christmas Wonderland Ltd | Wholesale & retail | 2026 |
| Burgundy Moonlight Ltd | Information & communication | 2024 |
| Burley Yard Ltd | Real estate | 2026 |
| Burnett & Associates Limited | Financial services | 1980 |
| Burras (2003) Limited | Professional & scientific | 2003 |
| Burras Limited | Construction | 1979 |
| Burrow Interpreting (BSL) Limited | Professional & scientific | 2026 |
| Burston Ridge Farm Developments Ltd | Real estate | 2023 |
| Bury Mews Limited | Households | 2008 |
| Bury Road Management Company Limited | Households | 1983 |
| Business Consulting & Accounting Limited | Professional & scientific | 2005 |
| Business Control Services Limited | Professional & scientific | 2002 |
| Business Critical Engineering Limited | Professional & scientific | 2016 |
| Business Energy Limited | Administrative & support | 1993 |
| Butchers Developments Limited | Construction | 2023 |
| Buttery Consulting Limited | Professional & scientific | 2026 |
| Buzz Arnold Citroen Limited | Wholesale & retail | 2004 |
| BW Bathrooms Limited | Construction | 2025 |
| BWC Developments Southern Ltd | Construction | 2020 |
| Bwhns Limited | Health & social care | 2022 |
| BWT International Ltd | Information & communication | 2020 |
| Byer Properties Limited | Real estate | 2019 |
| BZ Carpet Care Ltd | Administrative & support | 2026 |
| C & a Cleaning Services Ltd | Administrative & support | 2019 |
| C & C Property UK Developments Ltd | Real estate | 2018 |
| C & C White Limited | Administrative & support | 2016 |
| C & J Dopson Ltd | Administrative & support | 2016 |
| C & M Roofing (and Building Contractor) Ltd | Construction | 2007 |
| C C S S Limited | Construction | 2017 |
| C Conway Groundworks Ltd | Construction | 2024 |
| C D Lawrie & Sons Limited | Hospitality | 2009 |
| C FOX Decorators Ltd | Construction | 2010 |
| C Hardy Holdings Limited | Financial services | 2025 |
| C Howard Properties Limited | Real estate | 2022 |
| C Hughes Brickwork and Construction Ltd | Construction | 2022 |
| C I I S East Limited | Financial services | 2003 |
| C J Waste Services Limited | Water & waste | 2012 |
| C Lillington Carpentry & Building Services Limited | Construction | 2021 |
| C M D Portsmouth Ltd | Other services | 2017 |
| C M Roofing Ltd | Extraterritorial | 2012 |
| C P Plant Hire Ltd | Administrative & support | 2005 |
| C Page Construction Ltd | Construction | 2017 |
| C Parnell Construction Ltd | Construction | 2021 |
| C R J Electrical Limited | Construction | 1999 |
| C S Randall Plumbing & Heating Limited | Construction | 2011 |
| C&C Industrial Roofing Ltd | Construction | 2016 |
| C&D Trees Limited | Agriculture & fishing | 2015 |
| C&G Limited | Real estate | 2023 |
| C&G Pharma Ltd | Wholesale & retail | 2025 |
| C&J Caribbean Foods Ltd | Agriculture & fishing | 2026 |
| C&S Consulting Limited | Hospitality | 2025 |
| C&S Lettings Limited | Real estate | 2019 |
| C&V Consulting Services Limited | Administrative & support | 2015 |
| C-Hawk Analytics Ltd | Information & communication | 2026 |
| C.B. Hughes Limited | Financial services | 1998 |
| C.Cheesman Limited | Wholesale & retail | 2026 |
| C.D. Bryant Limited | Manufacturing | 2003 |
| C.D.M Contractors Ltd | Construction | 2008 |
| C.G. Spratt & SON Limited | Real estate | 2003 |
| C.G.S Communications Ltd | Construction | 2022 |
| C.K.B. Property Limited | Real estate | 2004 |
| C.K.B. Trading Limited | Extraterritorial | 1989 |
| C.M Interior Solutions Limited | Construction | 2024 |
| C.Mckeigue Construction Ltd | Construction | 2002 |
| C.P.Rudge & Sons,Limited | Agriculture & fishing | 1960 |
| C.S. Medical Consultancy Services Limited | Health & social care | 2013 |
| C2 Trade Ltd | Wholesale & retail | 2025 |
| C4 Competitions Ltd | Other services | 2024 |
| C4 Plumbing & Heating Ltd | Construction | 2022 |
| C45 Commercial Properties Limited | Construction | 2024 |
| C45 Group Limited | Financial services | 2024 |
| C45 Investment Properties Limited | Real estate | 2024 |
| C45 Limited | Construction | 2017 |
| C5 Consultancy Ltd | Information & communication | 2006 |
| Cable Connections Ltd | Construction | 2016 |
| Cactus Projects Limited | Construction | 2017 |
| Cade Facade Ltd | Construction | 2022 |
| Cadlington House Management Limited | Households | 2009 |