| Breaking Silos Ltd | Professional & scientific | 2026 |
| Breath of Fresh Air (Southampton) Limited | Health & social care | 2022 |
| Breath Work Studio UK Ltd | Health & social care | 2026 |
| Breeze Health Ltd | Health & social care | 2021 |
| Brettex Properties Ltd | Real estate | 2022 |
| Brian COX & Company Limited | Real estate | 2004 |
| Brickstones Limited | Administrative & support | 2009 |
| Bridge Street Commercial Ltd | Real estate | 2020 |
| Bright Trade Ltd | Information & communication | 2018 |
| Brighter Web Ltd | Information & communication | 2026 |
| Brill Storage Ltd | Real estate | 2020 |
| Broadbridge Investments Limited | Administrative & support | 1945 |
| Broadgate Freeholds Limited | Real estate | 2009 |
| Broomco (3971) Limited | Financial services | 2005 |
| Brothers Installations Limited | Manufacturing | 2010 |
| BRS Trading Limited | Financial services | 2016 |
| Brumdogs Ltd | Hospitality | 2024 |
| Brushlinks Ltd | Professional & scientific | 2022 |
| Bsbi Consulting Limited | Information & communication | 2014 |
| BSS Site Services Limited | Construction | 2016 |
| Bthh Properties Ltd | Real estate | 2024 |
| BTV Car Storage Limited | Health & social care | 2017 |
| BU4U Fitness Limited | Arts & recreation | 2022 |
| BU4U Limited | Arts & recreation | 2022 |
| Bubblestorm Ltd | Professional & scientific | 2025 |
| Bucks Roofing and Building Ltd | Construction | 2020 |
| Buddi Limited | Manufacturing | 2004 |
| Buddi Sensors Limited | Information & communication | 2024 |
| Bugler Developments Limited | Construction | 1981 |
| Bugler Group Limited | Construction | 2001 |
| Bugler Homes Limited | Construction | 2001 |
| Bugler Land Limited | Real estate | 2016 |
| Bugler Property Services Limited | Extraterritorial | 2024 |
| Bugler Regeneration Limited | Construction | 2025 |
| Buildco London Ltd | Construction | 2021 |
| Builders of Croxley Ltd | Construction | 2020 |
| Building Technology & Safety Services Limited | Professional & scientific | 2024 |
| Bulgarian School Watford Limited | Education | 2015 |
| Bulk Transfer (London) Limited | Transport & logistics | 2008 |
| Bulk Transfer Ltd | Water & waste | 2006 |
| Bullsland Renewables Limited | Real estate | 2023 |
| Bumblebeesimpex Ltd | Wholesale & retail | 2024 |
| Bunch & Duke Property Management Limited | Administrative & support | 2000 |
| Burdett and King Limited | Real estate | 2015 |
| Burleigh Dell Developments Limited | Construction | 2020 |
| Burren Investments Limited | Real estate | 1998 |
| Busch Graphic Machinery UK Limited | Professional & scientific | 2009 |
| Business Solution Strategy Limited | Professional & scientific | 2025 |
| Business Solutions Strategy Limited | Professional & scientific | 2017 |
| Butler House Management Limited | Households | 2002 |
| Butterfly International Ltd | Professional & scientific | 2024 |
| Buysco Limited | Construction | 2012 |
| BWB Gaming Limited | Wholesale & retail | 2021 |
| Byrne Windows Limited | Construction | 2024 |
| Byte PM Ltd | Information & communication | 2017 |
| Bytebound Media Ltd | Professional & scientific | 2025 |
| C & C Property Investment Limited | Construction | 2014 |
| C & R Risk Management Limited | Financial services | 2024 |
| C Connor Ltd | Construction | 2023 |
| C L Sons Ltd | Wholesale & retail | 2020 |
| C P Flynn Plumbing & Heating Ltd | Construction | 2022 |
| C. & P. Graphics Limited | Professional & scientific | 2009 |
| C.E.O.1983 Ltd | Construction | 2020 |
| C.L Electrical Solutions Limited | Construction | 2022 |
| Cacchino Ltd | Wholesale & retail | 2022 |
| Cadenz Limited | Professional & scientific | 2018 |
| Cadwell IT Services Limited | Professional & scientific | 2004 |
| Cairnpark Properties Limited | Construction | 2000 |
| Cait Group Ltd | Education | 2024 |
| Calbar Properties Ltd | Real estate | 2007 |
| Caledonian Automotive Recruitment Limited | Administrative & support | 2019 |
| Caledonian Building Services Limited | Administrative & support | 2019 |
| Caledonian Construction Services Limited | Administrative & support | 2019 |
| Caledonian Recruitment Group Limited | Professional & scientific | 2019 |
| Callender Concepts Limited | Administrative & support | 2016 |
| Calonzo Ltd | Wholesale & retail | 2022 |
| Caluka Consulting Limited | Professional & scientific | 2018 |
| Camberwell Properties Limited | Real estate | 2019 |
| Camdor Global Assets Ltd | Real estate | 2024 |
| Camelot Capital Ltd | Real estate | 2026 |
| Cameo Properties Limited | Real estate | 2000 |
| Cameron & Associates Limited | Professional & scientific | 1999 |
| Campbeltown Advisory Ltd | Financial services | 2026 |
| Candlelite Couriers Ltd | Wholesale & retail | 2024 |
| Candlemas Holdings Limited | Real estate | 2018 |
| Candlemas Properties Limited | Real estate | 2019 |
| Cando Consulting Group Ltd | Professional & scientific | 2020 |
| Candy Developments (Hitchin) Ltd | Construction | 2021 |
| Candy Developments Ltd | Construction | 2017 |
| Capital Construction London Ltd | Construction | 2025 |
| Capital Hire Limited | Administrative & support | 1998 |
| Capital Landscapers Limited | Administrative & support | 2012 |
| Capital Oak Tree Care Ltd | Administrative & support | 2025 |
| Capital Property Management & Investment Limited | Extraterritorial | 2002 |
| Capsule Solutions Limited | Professional & scientific | 2021 |
| Captev Ltd | Financial services | 2024 |
| Car Planet Trading Limited | Wholesale & retail | 2022 |
| Cara Decor Ltd | Construction | 2025 |
| Caracara Energy Limited | Professional & scientific | 2013 |
| Cardaddys Limited | Wholesale & retail | 2025 |