| Birchwood Court Management Company Limited | Households | 1992 |
| Birchwood Grove (Caxton) Limited | Construction | 2026 |
| Birchwood Plant Hire Limited | Administrative & support | 2015 |
| Birkdale Motors Bedford Ltd | Wholesale & retail | 2004 |
| Birkdale Payment Services Limited | Professional & scientific | 2017 |
| Birmon Trading Group Ltd | Wholesale & retail | 2020 |
| Biryano Ltd | Hospitality | 2025 |
| Bishopsgate Financial Consulting Limited | Information & communication | 2008 |
| Biskaya Limited | Hospitality | 2021 |
| Bisma Direct Limited | Transport & logistics | 2026 |
| Bismillah Signs Limited | Extraterritorial | 2011 |
| Bismillah Vehicles Ltd | Administrative & support | 2022 |
| Bisspod Care Limited | Health & social care | 2020 |
| Bitbite Limited | Information & communication | 2025 |
| Bitels Transport Ltd | Transport & logistics | 2018 |
| Bites of Punjab Limited | Hospitality | 2025 |
| Bites With Hope UK Ltd | Extraterritorial | 2021 |
| Bitgrove Limited | Information & communication | 2008 |
| Bivent Limited | Administrative & support | 2023 |
| Bivol Construct Ltd | Construction | 2018 |
| Bivowac Estates Limited | Real estate | 2015 |
| Bivowac Investments Limited | Real estate | 2017 |
| Bixspur Holdings Ltd | Real estate | 2022 |
| BJE Rentals Ltd | Real estate | 2024 |
| Bjmb Ltd | Real estate | 2024 |
| BK Interior Space Ltd | Construction | 2026 |
| BK Medics Ltd | Health & social care | 2022 |
| BKA Private EYE Practice Ltd | Health & social care | 2026 |
| BKL Construct Ltd | Construction | 2025 |
| BKO Media Ltd | Information & communication | 2024 |
| Bkph Ltd | Construction | 2012 |
| BL Childminding Ltd | Health & social care | 2021 |
| Black Cat Guitars Limited | Professional & scientific | 2014 |
| Black Electrical Family Limited | Construction | 2023 |
| Black Excellence in Tech CIC | Administrative & support | 2024 |
| Black Hair Essentials Limited | Wholesale & retail | 2016 |
| Black Knees Ltd | Construction | 2024 |
| Black Knight Financial Services Limited | Financial services | 2025 |
| Black Knight Investments Limited | Real estate | 2022 |
| Black Moor Farm Business Park Management Company Limited | Transport & logistics | 2006 |
| Black Spot Rigging Ltd | Information & communication | 2010 |
| Black Star Consultancy Ltd | Hospitality | 2015 |
| Blackbridge TGS 1 Limited | Energy | 2014 |
| Blackfin Incentive Limited | Professional & scientific | 2015 |
| Blacklock Doors & Security Limited | Administrative & support | 2001 |
| Blackridge Automotive Ltd | Wholesale & retail | 2008 |
| Blackridge Capital Group Ltd | Real estate | 2026 |
| Blackrock Scaffolding Limited | Construction | 2014 |
| Blacksmiths Court Limited | Extraterritorial | 2003 |
| Blackstand International Corporation Ltd | Transport & logistics | 2020 |
| Blackstar Software Limited | Information & communication | 2017 |
| Blackston Coopers Consulting Ltd | Information & communication | 2018 |
| Blackwood Trade & Co. Limited | Wholesale & retail | 2026 |
| Blacs Group Ltd | Wholesale & retail | 2025 |
| Blade Flooring Ltd | Construction | 2018 |
| Bladetechs International Ltd | Administrative & support | 2015 |
| Bladz Ltd | Other services | 2025 |
| Blajon Asset Management Limited | Real estate | 2025 |
| Blakamix Int'L Ltd | Manufacturing | 1996 |
| Blake & Melbourne Property Ltd | Real estate | 2024 |
| Blakeland Homes Limited | Construction | 2021 |
| Blanche NEF Limited | Professional & scientific | 2021 |
| Blantyre Management Limited | Wholesale & retail | 1979 |
| Blaxfx Finance Ltd | Professional & scientific | 2022 |
| Blazeko Ltd | Transport & logistics | 2014 |
| BLD Protection Ltd | Financial services | 2021 |
| Bleak Hall Sports Ltd | Wholesale & retail | 2022 |
| Blenheim IT Limited | Information & communication | 2007 |
| Bleu Holdings Limited | Financial services | 2019 |
| Blick Building Contractors Ltd | Construction | 2014 |
| Bliss Clinical Research Ltd. | Health & social care | 2022 |
| Bliss Medics Ltd | Health & social care | 2024 |
| Blisshealth Concepts Ltd | Health & social care | 2022 |
| Blitz Bargains Ltd | Wholesale & retail | 2025 |
| Blitz Car Hire Ltd | Administrative & support | 2023 |
| Blitz Cleaning and Maintenance Ltd | Construction | 2024 |
| BLK Properties Ltd | Real estate | 2022 |
| Block Sphere Ltd | Information & communication | 2021 |
| Blocked Urinal.Com Limited | Other services | 2023 |
| Blockhaus Retail Ltd | Wholesale & retail | 2020 |
| Bloody Surgery Ltd. | Health & social care | 2009 |
| Bloom Extensions Ltd | Construction | 2025 |
| Bloom Landscapes UK Limited | Administrative & support | 2026 |
| Bloomin' Well CIC | Agriculture & fishing | 2023 |
| Blossom Cafe Ltd | Hospitality | 2018 |
| Blossom Weddings and Events Ltd | Hospitality | 2021 |
| BLR Services Limited | Manufacturing | 2024 |
| Blue BAG Distribution Ltd | Transport & logistics | 2017 |
| Blue Bear Builds Limited | Construction | 2024 |
| Blue Bear Invests Limited | Real estate | 2026 |
| Blue Burgundy Limited | Professional & scientific | 2019 |
| Blue Chilli Flying Limited | Arts & recreation | 2016 |
| Blue Chip Limited | Extraterritorial | 2009 |
| Blue Chip Parts Limited | Information & communication | 1999 |
| Blue Circle Recruitment Ltd | Administrative & support | 2022 |
| Blue Cloud Management Limited | Professional & scientific | 2001 |
| Blue Conker Limited | Real estate | 2015 |
| Blue Creation Tech Ltd | Manufacturing | 2024 |
| Blue Cube (Europe) Ltd | Other services | 2015 |
| Blue Diamond Assets Ltd | Real estate | 2014 |