| Braver Property Group Limited | Financial services | 2022 |
| Breakspear Estate Management Ltd | Households | 2025 |
| Breakspear Mews Courtyard Ltd | Households | 2025 |
| Breathe Move & Inspire Ltd | Health & social care | 2021 |
| Breazy Ltd | Wholesale & retail | 2025 |
| Breeze Services Ltd | Administrative & support | 2023 |
| Brefts Flooring Ltd | Manufacturing | 2025 |
| Brendog Services Ltd | Other services | 2023 |
| Brick and Pillar Ltd | Construction | 2026 |
| Brick Capital Investments Limited | Real estate | 2026 |
| Brickforge Ltd | Construction | 2026 |
| Brickmaster Creations Ltd | Construction | 2024 |
| Brickstone Innovations Ltd | Construction | 2024 |
| Bricky in London Ltd | Construction | 2023 |
| Bridge Capital Finance Ltd | Construction | 2025 |
| Bridge Housing Solutions Limited | Information & communication | 2013 |
| Bridge International Consultancy and Migration Limited | Hospitality | 2022 |
| Bridge Solutions Group Limited | Financial services | 2023 |
| Bridge Technology International Limited | Construction | 1999 |
| Bridgewood Homes Ltd | Real estate | 2017 |
| Bright Bridge International Limited | Administrative & support | 2026 |
| Bright Care Limited | Health & social care | 2000 |
| Brighter Lights Entertainment Ltd | Arts & recreation | 2024 |
| Brightline Electrical Ltd | Manufacturing | 2025 |
| Brij Recruitment Solutions Ltd | Other services | 2022 |
| Brilliant Minds Open Talent CIC | Administrative & support | 2021 |
| Bristol CC Limited | Wholesale & retail | 2025 |
| Bristol-Myers Squibb/Astrazeneca Ukeig | | 2008 |
| Britannia Dwellings Ltd | Construction | 2025 |
| Britex Trade Supplies Ltd | Wholesale & retail | 2026 |
| Britindia Private Limited | Transport & logistics | 2025 |
| British Alcan Primary and Recycling Limited | Professional & scientific | 1959 |
| British Alcan Rolled Products Limited | Professional & scientific | 1939 |
| Britmed Healthcare Private Limited | Extraterritorial | 2026 |
| Britmedicare Ltd | Health & social care | 2023 |
| Briton IT Ltd | Wholesale & retail | 2025 |
| Brittain Investment Group Ltd | Financial services | 2026 |
| Britway Air Real Estate Limited | Real estate | 2024 |
| Britway Airport Transfer Limited | Transport & logistics | 2018 |
| Britway Executive Coaches Ltd | Transport & logistics | 2026 |
| Britway Export Limited | Wholesale & retail | 2023 |
| Britway Services Limited | Information & communication | 2014 |
| Brixmore Limited | Real estate | 2020 |
| Broadaxe Homes Limited | Construction | 2024 |
| Broadberry Data Systems Limited | Wholesale & retail | 1993 |
| Broadcast Reach Limited | Information & communication | 2022 |
| Broadway & Shield Limited | Construction | 2019 |
| Brokery Finance Ltd | Financial services | 2026 |
| Brokery Ltd | Financial services | 2024 |
| Brokery Properties Ltd | Real estate | 2025 |
| Bromyard Capital Limited | Information & communication | 2013 |
| Brook Street (UK) Limited | Administrative & support | 1948 |
| Brook Street Bureau Limited | Professional & scientific | 1996 |
| Brooklyn Properties Management Limited | Real estate | 2021 |
| Brooks Comms Ltd | Information & communication | 2021 |
| Broomlaw 24 Ltd | Real estate | 2021 |
| Brother Electrical Ltd | Construction | 2018 |
| Brousco Limited | Professional & scientific | 2015 |
| Brown Tree Ltd | Real estate | 2023 |
| Browndog Scenery Limited | Professional & scientific | 2024 |
| Browns Luxury Services Ltd | Transport & logistics | 2022 |
| Browns Models Limited | Professional & scientific | 2024 |
| Bruconn Ltd | Information & communication | 2016 |
| Brunel Lodge Limited | Hospitality | 2013 |
| Brunel University Enterprises Limited | Financial services | 2001 |
| Brusketta UK Ltd | Hospitality | 2024 |
| Bryan Quality & Engineering Associates Limited | Transport & logistics | 2016 |
| Bryllex Limited | Construction | 2026 |
| Bryson Express Limited | Transport & logistics | 2004 |
| BS Loft & Extensions Ltd | Construction | 2021 |
| BS Project Services Limited | Administrative & support | 1980 |
| BS Roofing Services Ltd | Construction | 2019 |
| BSI Property Investments Ltd | Real estate | 2017 |
| BSN Flooring Services Ltd | Construction | 2008 |
| BSR Technologies Limited | Information & communication | 2009 |
| Btdt Coffee Limited | Hospitality | 2020 |
| Btej Construction Ltd | Construction | 2013 |
| Btej Kitchen & Bedrooms Ltd | Construction | 2021 |
| Btej Properties Ltd | Real estate | 2019 |
| Bubble & Boba Ltd | Hospitality | 2022 |
| Bubble Girl Ltd | Wholesale & retail | 2023 |
| Bubble Tea Supplier Ltd | Wholesale & retail | 2019 |
| Bubbles & Cuddles Limited | Wholesale & retail | 2019 |
| Bubluda Limited | Hospitality | 2021 |
| Buchanan House Limited | Households | 1993 |
| Buck House (Chesham) Management Company Limited | Households | 2015 |
| Buckinghamshire House Ltd | Real estate | 2024 |
| Buckland Ltd | Real estate | 2026 |
| Budd Technical Services Ltd | Other services | 2011 |
| Budget DMC UK Ltd | Administrative & support | 2025 |
| Budget Tyres (Uxbridge) Ltd | Wholesale & retail | 2016 |
| Budh Estates Limited | Real estate | 2023 |
| Budminster Limited | Arts & recreation | 2016 |
| Buen Gusto Limited | Hospitality | 2010 |
| Buena Limited | Professional & scientific | 2023 |
| Build Master London Ltd | Construction | 2026 |
| Build on Properties Ltd | Real estate | 2018 |
| Building Energy Solution Techniques Limited | Construction | 2017 |
| Building IQ Limited | Manufacturing | 2016 |
| Building Services and Maintenance Ltd | Construction | 2022 |