| Bethmar Limited | Construction | 2013 |
| Bfun Limited | Arts & recreation | 2026 |
| BG Dynamics Ltd | Wholesale & retail | 2024 |
| Bhakti Rasa Ltd | Health & social care | 2024 |
| BI Autocentres Ltd | Wholesale & retail | 2009 |
| Biens Limited | Information & communication | 2024 |
| Big Bear and KIN Ltd | Wholesale & retail | 2023 |
| Big Stick Communications Limited | Professional & scientific | 2003 |
| Bilal EL Khan Ltd | Professional & scientific | 2026 |
| Bill Rocker Ltd | Information & communication | 2022 |
| Billgo 2 Ltd | Administrative & support | 2015 |
| Billgo Ltd | Construction | 2014 |
| Bin'Auf Limited | Wholesale & retail | 2018 |
| Bio-Synergix International Ltd | Professional & scientific | 2019 |
| Birdcage Bridal Boutique Limited | Manufacturing | 2017 |
| Biscoff Property Holdco Limited | Financial services | 2021 |
| Biscoff Property Limited | Construction | 2021 |
| Bishopsgate Contracts Limited | Construction | 1993 |
| Bishopsgate INS Group Ltd | Financial services | 2026 |
| Bishopsline Ltd | Administrative & support | 2010 |
| Bizibl Group Limited | Information & communication | 2014 |
| Bizibl Technology Limited | Information & communication | 2014 |
| Bizzy Bees Nursery Limited | Education | 2008 |
| BL Groundworks Ltd | Construction | 2021 |
| BL Skills Consulting Ltd | Information & communication | 2019 |
| BL the Future Ltd | Construction | 2023 |
| Black Lion Hill WD7 Ltd | Other services | 2019 |
| Black Point Recruitment Ltd | Administrative & support | 2017 |
| Blackgold Properties Limited | Real estate | 2017 |
| Blackshire Services Ltd | Construction | 2026 |
| Blacktop Asphalt Ltd | Manufacturing | 2025 |
| Blade Traders Limited | Other services | 2024 |
| Blanc Hub Limited | Transport & logistics | 2025 |
| BLG Collection Ltd | Wholesale & retail | 2019 |
| Blippy's PVT Ltd | Hospitality | 2025 |
| Blis Acu-Herbs Limited | Health & social care | 2023 |
| Blose Architectural Services Ltd | Professional & scientific | 2017 |
| Blue Door Funding Limited | Financial services | 2025 |
| Blue Marubi Ltd | Wholesale & retail | 2017 |
| Blue Onyx Property Limited | Real estate | 2024 |
| Blue Slab Limited | Financial services | 2024 |
| Bluebells Care Limited | Health & social care | 2023 |
| Blueberry Hill Care Limited | Health & social care | 2016 |
| Bluespark Design & Build Ltd | Construction | 2018 |
| BMP Translations Ltd. | Professional & scientific | 2015 |
| BMX Academy Limited | Arts & recreation | 2015 |
| BNN Africa Ltd | Information & communication | 2025 |
| Boden Haste Limited | Transport & logistics | 2024 |
| Body Smart Repairs Limited | Wholesale & retail | 2006 |
| Body Therapy Hyperbaric Oxygen and Drug Free Healing Ltd | Health & social care | 2019 |
| Body Therapy Vital Ltd | Wholesale & retail | 2024 |
| Bolani Pizza Limited | Hospitality | 2025 |
| Bolinton Limited | Construction | 2020 |
| Bolt Technical Limited | Administrative & support | 2025 |
| Bonell Holdings Limited | Financial services | 2025 |
| Bonfire Technologies Limited | Information & communication | 2020 |
| Bonney Tech Ltd | Information & communication | 2025 |
| Bonsai Bored Ltd | Financial services | 2021 |
| Borough Housing Limited | Real estate | 2009 |
| Boss Plumbing Services Ltd | Construction | 2025 |
| Boston Pizza Company Limited | Hospitality | 1998 |
| Bourne END Residential Management Company Limited | Households | 2019 |
| Boutique Tours Ltd | Administrative & support | 2018 |
| Bowen & Sons Limited | Construction | 2006 |
| Bowshackle Ltd | Construction | 2014 |
| BP Property Solutions (London) Ltd | Real estate | 2023 |
| BQ Care Ltd | Health & social care | 2022 |
| Bray (Oakham) Limited | Real estate | 2021 |
| Bray (Welwyn) Limited | Construction | 2021 |
| Brendan Wright Mechanical Ltd | Manufacturing | 2014 |
| Brewster Mcmillan Ltd | Wholesale & retail | 2022 |
| Bridge Road Management Limited | Real estate | 2020 |
| Bridge Steps Supported Living Services Ltd | Health & social care | 2025 |
| Bridge Trade Ltd | Wholesale & retail | 2026 |
| Bright Hawk Ltd | Professional & scientific | 2023 |
| Brill Investments Ltd | Construction | 2023 |
| Brilliant BIT Ltd | Information & communication | 2006 |
| Brimpton House Nursery Limited | Education | 2005 |
| Broadcast Service Partners Ltd | Information & communication | 2023 |
| Brocket Hall (Holding) Limited | Professional & scientific | 2019 |
| Brocket Hall Golf & Country Club Limited | Arts & recreation | 2024 |
| Brogan Group Holdings Ltd | Professional & scientific | 2015 |
| Brogan Group Ltd | Construction | 2006 |
| Brogan Group Property Ltd | Real estate | 2015 |
| Brogan Group UK Limited | Construction | 1988 |
| Brogan Plant Hire Ltd | Administrative & support | 2015 |
| Brogan Powered Access Ltd | Construction | 2014 |
| Broste Rivers Group Limited | Construction | 2016 |
| Broughton Retail Park Nominee 1 Limited | Administrative & support | 2001 |
| Broughton Retail Park Nominee 2 Limited | Administrative & support | 2001 |
| Broughton Retail Park Nominee 3 Limited | Administrative & support | 2001 |
| Broughton Retail Park Nominee 4 Limited | Administrative & support | 2001 |
| Brown Dog Building Ltd | Construction | 2025 |
| Brunel Construction Services Limited | Construction | 2019 |
| BTK Fitness & Coaching Ltd | Education | 2020 |
| Buckingham Therapeutics Ltd | Wholesale & retail | 2020 |
| Buckinghamshire Nursery Schools Ltd | Education | 2002 |
| Build Insight Ltd | Professional & scientific | 2013 |
| Build on Time Limited | Construction | 2010 |
| Build UP Ltd | Construction | 2026 |