| Bitterne Road LLP | | 2011 |
| Bitterne Village Convenience Limited | Wholesale & retail | 2022 |
| Bixbite Ltd | Hospitality | 2017 |
| Biz-Extras Ltd | Professional & scientific | 2025 |
| Bizafy Limited | Professional & scientific | 2022 |
| Bizlog Ltd | Information & communication | 2018 |
| Bizon Services Ltd | Transport & logistics | 2016 |
| Bizzwin Horizon Ltd | Professional & scientific | 2025 |
| Bizzy Bounce Ltd | Arts & recreation | 2020 |
| BJC Design South East Ltd | Professional & scientific | 2019 |
| BJN Limited | Real estate | 2006 |
| BJS Conservation Ltd | Administrative & support | 2003 |
| BK Developers Ltd | Construction | 2021 |
| BK Properties Limited | | 1989 |
| Bkft Trading Limited | Wholesale & retail | 2011 |
| BKJ Logistics Limited | Wholesale & retail | 2011 |
| Bkjp Limited | Other services | 2024 |
| BKK Property Investments Ltd | Real estate | 2020 |
| Bktranspolink Limited | Transport & logistics | 2025 |
| BKV Solutions Ltd | Wholesale & retail | 2022 |
| BKVC1 Limited | Real estate | 2013 |
| BKVC2 Limited | Real estate | 2015 |
| Bl-Sales Limited | Wholesale & retail | 2025 |
| Blabey Engineering Limited | Manufacturing | 2013 |
| Blache Helicopters Services Ltd | Manufacturing | 2017 |
| Black Antler Ltd | Professional & scientific | 2018 |
| Black Bear (Moreton) Limited | Hospitality | 2019 |
| Black Book Executive Travel Ltd | Transport & logistics | 2019 |
| Black Box Media Marketing Ltd | Information & communication | 2023 |
| Black Coffee Technology Limited | Information & communication | 2023 |
| Black Dog Kitchen Ltd | Hospitality | 2025 |
| Black Dogs Consulting Ltd | Professional & scientific | 2008 |
| Black Forest Properties Limited | Real estate | 2020 |
| Black FOX Construction Limited | Construction | 2015 |
| Black FOX Estates Ltd | Real estate | 2018 |
| Black FOX Glazing Limited | Construction | 2019 |
| Black Ginger Kitchen Ltd | Hospitality | 2024 |
| Black History Month South C.I.C. | Administrative & support | 2018 |
| Black House Hampshire Ltd | Construction | 2026 |
| Black INK Tattoo Limited | Other services | 2024 |
| Black IS Gold by MB Ltd | Manufacturing | 2024 |
| Black Knights Infrastructure Ltd | Information & communication | 2025 |
| Black Pepper Indian Restaurant Ltd | Hospitality | 2019 |
| Black Property & Investments Limited | Financial services | 2024 |
| Black Sheep Investment Holdings Ltd | Real estate | 2020 |
| Black Star Records Limited | Wholesale & retail | 2020 |
| Black Swan Financial Services Ltd | Financial services | 2014 |
| Black Swan UK Holdings Ltd | Financial services | 2019 |
| Black Talent Limited | Administrative & support | 2022 |
| Black Triangle Solution Limited | Manufacturing | 2015 |
| Black Velvet Productions Co Limited | Hospitality | 2025 |
| Black WAX Coffee Ltd | Hospitality | 2022 |
| Black Wine Storage Limited | Administrative & support | 2022 |
| Blackboard Canteen Ltd | Hospitality | 2023 |
| Blackbrook Integrated Technology Limited | Information & communication | 1994 |
| Blackdown Asset Management Limited | Financial services | 2024 |
| Blackdragon Films Limited | Extraterritorial | 2025 |
| Blackfield and Langley FC Ltd | Arts & recreation | 2026 |
| Blackfield Garage Services Limited | Wholesale & retail | 2000 |
| Blackford Brothers Limited | Information & communication | 2018 |
| Blackhawk 4X4 Ltd | Wholesale & retail | 2023 |
| Blackmont Ltd | Real estate | 2026 |
| BLACKONYX-72AG Ltd | Real estate | 2025 |
| Blackpool (50-52 Topping Street) Ltd | Construction | 2019 |
| Blackroock Ltd | Wholesale & retail | 2023 |
| Blacksmith Haus Apartments Ltd | Real estate | 2025 |
| Blackstone Housing Limited | Hospitality | 2015 |
| Blackvolt Ltd | Wholesale & retail | 2025 |
| Blackwell Forest Limited | Agriculture & fishing | 2021 |
| Blade Consultancy Limited | Professional & scientific | 2013 |
| Blade Works Ltd | Manufacturing | 2025 |
| Bladed Permanent Makeup Ltd | Other services | 2026 |
| Bladon Energy Group Ltd | Other services | 2021 |
| Blake & Blake Asset Management Consulting Ltd | Professional & scientific | 2021 |
| Blake Computing Solutions Ltd | Information & communication | 2024 |
| Blake Interactive Limited | Information & communication | 2024 |
| Blakes Lavac Taylors Limited | Extraterritorial | 1998 |
| Blanchard Wells (Groundworks Contractors) Limited | Construction | 2009 |
| Blanchard Wells (Holdings) Limited | Financial services | 2001 |
| Blanchard Wells (Plant Hire) Limited | Administrative & support | 2001 |
| Blanchard Wells Civils & Structures Limited | Construction | 2022 |
| Blanchard Wells Limited | Construction | 2000 |
| Blanchard Wells Properties Limited | Real estate | 2014 |
| Blank Canvas Building Contractors Ltd | Construction | 2014 |
| Blaq Biscuit Ltd | Health & social care | 2021 |
| Blarksurs Limited | Health & social care | 2018 |
| Blaster Ltd | Extraterritorial | 2023 |
| Blay Enterprises Limited | Information & communication | 2017 |
| Blaymires Property Limited | Real estate | 2021 |
| Blaymires Recruitment Limited | Administrative & support | 2020 |
| Blaze Communication L&D Ltd | Information & communication | 2020 |
| Blazex Laser Technology Ltd | Wholesale & retail | 2025 |
| Blco Ltd | Financial services | 2002 |
| Bldetailing&Mobilevaleting Ltd | Administrative & support | 2026 |
| Blenheim Court Freeholders Limited | Households | 1999 |
| Blenheim Gardens (Dibden Purlieu) Management Company Limited | Households | 2022 |
| Bless Healthcare Services Ltd | Health & social care | 2025 |
| Blessed Property Solutions Limited | Real estate | 2017 |
| Bletchley Developments Limited | Construction | 2017 |
| BLH Hold Co Ltd | Professional & scientific | 2025 |