| BL Red Limited | Information & communication | 2008 |
| Black TIP Reef Limited | Hospitality | 2003 |
| Blackhall Homes Ltd | Real estate | 2020 |
| Blakemore Residential Limited | Real estate | 2025 |
| Blakeney Holdings Limited | Professional & scientific | 1990 |
| Blank Page Films Ltd | Information & communication | 2022 |
| Blanket Rentals Limited | Real estate | 2018 |
| BLD Trading Ltd | Wholesale & retail | 2024 |
| Blenheim Park Freehold Limited | Households | 2021 |
| Blissfintech Ltd | Professional & scientific | 2021 |
| Blockshift Partners Limited | Professional & scientific | 2024 |
| Bloom Alloy Limited | Manufacturing | 2025 |
| Bloom Holdings Limited | Households | 2019 |
| Bloomingo Ltd | Wholesale & retail | 2022 |
| Blossom Bidco Limited | Professional & scientific | 2024 |
| Blossom Exquisite Caterers Ltd | Hospitality | 2026 |
| Blossom Midco Limited | Professional & scientific | 2024 |
| Blossom Properties ML Ltd | Construction | 2021 |
| Blossom Topco Limited | Professional & scientific | 2024 |
| Blossoms Day Nursery Limited | Education | 2004 |
| Blue Door 22 Elgin Road Limited | Households | 2008 |
| Blue Flowers Music 2010 Ltd | Arts & recreation | 2010 |
| Blue Highlands Ltd | Real estate | 2020 |
| Blue Sky Window Cleaning Ltd | Other services | 2018 |
| Blue Tree (Supported) Homes Ltd | Public administration | 2024 |
| Bluebridge Interiors Limited | Professional & scientific | 2015 |
| Boad Ventures Ltd | Health & social care | 2014 |
| Body Coast Limited | Manufacturing | 2015 |
| Boilermatic Limited | Construction | 2024 |
| Bombons Ltd | Manufacturing | 2018 |
| Bonars Construction Ltd | Construction | 2011 |
| Bonington House (Freehold) Limited | Households | 1998 |
| Bookempress Limited | Manufacturing | 2018 |
| Boomio Productions Ltd | Information & communication | 2023 |
| Bosco Plumbing Services Ltd | Administrative & support | 2016 |
| Bosjam Delivery & Household Clearance Limited | Transport & logistics | 2016 |
| Bosl Administration Services Limited | Professional & scientific | 2016 |
| Bosl Management Services Limited | Professional & scientific | 2016 |
| Boss & Blade Ltd | Other services | 2025 |
| Bourne Estates and Management Limited | Real estate | 2023 |
| Boxivation Ltd | Health & social care | 2020 |
| Boxtag (UK) Ltd | Wholesale & retail | 2019 |
| BP Tiling (UK) Limited | Construction | 2011 |
| BR Mellow Motors Limited | Wholesale & retail | 2025 |
| Bradley Court(Sutton)Management Limited | Households | 1969 |
| Brainbox Learning Centre Ltd | Education | 2024 |
| Brainbox Organix Ltd | Administrative & support | 2025 |
| Brambledown Management (15/19) Limited | Professional & scientific | 1972 |
| Brand Guru Global Ltd | Professional & scientific | 2021 |
| Brandon Mead Management Limited | Real estate | 2010 |
| Brandout Ltd | Wholesale & retail | 2024 |
| Brdb Ltd | Hospitality | 2025 |
| Brickwood Estates Limited | Administrative & support | 1996 |
| Bridgeton Care Limited | Health & social care | 2024 |
| Bright City Projects Limited | Construction | 2014 |
| Bright Travel Solutions Ltd | Transport & logistics | 2025 |
| Brighture Ltd | Information & communication | 2014 |
| Brilliant Music Limited | Information & communication | 2009 |
| Brimarch Ltd | Professional & scientific | 2024 |
| Brittish Technologies Limited | Information & communication | 2020 |
| Brixton: Medical & Aesthetics Ltd | Other services | 2018 |
| Brkout Ltd | Information & communication | 2025 |
| Brock Property Ltd | Real estate | 2016 |
| Bromley Property Maintenance Ltd | Construction | 2025 |
| Brother Business Ltd | Real estate | 2016 |
| BRS Property Ltd | Real estate | 2015 |
| BSA Building Designers Ltd | Construction | 2012 |
| BTS Holdings Limited | Information & communication | 1980 |
| BTS Services Limited | Professional & scientific | 2013 |
| Bubltown Technology Group Limited | Information & communication | 2018 |
| Bubu Properties Limited | Real estate | 2026 |
| Budgie Productions Ltd | Arts & recreation | 2023 |
| Built 2 Last Group Ltd | Construction | 2017 |
| Bumbleduck Productions Ltd | Information & communication | 2024 |
| Bunkerbag Ltd | Professional & scientific | 2014 |
| Burke & Clemens Limited | Administrative & support | 1990 |
| Burleagh Services Ltd | Administrative & support | 2018 |
| Business Management and Leadership Business School Ltd | Education | 2023 |
| Business Startup Services Online Ltd | Administrative & support | 2019 |
| Buy Hire Lease Ltd | Administrative & support | 2022 |
| Buzz Electrical Solutions Limited | Manufacturing | 2016 |
| C & D Limited | Manufacturing | 1984 |
| C B K Workspace Solutions Limited | Construction | 2018 |
| C J Beeston Consulting Ltd | Professional & scientific | 2020 |
| C.J.H. Plumbing & Heating Services Limited | Construction | 2015 |
| C3 Collaborating for Health | Health & social care | 2009 |
| C4 Cleaning Ltd | Administrative & support | 2013 |
| Caduso Group Limited | Professional & scientific | 2023 |
| Cairn Projects Ltd | Construction | 2023 |
| Cajan Limited | Wholesale & retail | 2026 |
| Calm Management Limited | Real estate | 2008 |
| Calmiga Properties Limited | Real estate | 2013 |
| Calpa Coombes Investments Limited | Financial services | 2026 |
| Cama Property Investment Ltd | Real estate | 2023 |
| Camelot London Construction Limited | Construction | 2025 |
| Campbell House Management Limited | Administrative & support | 1971 |
| Campbell's Cabs' Ltd | Administrative & support | 2012 |
| Campphire Limited | Construction | 2025 |
| Camsu Property Investment Ltd | Real estate | 2021 |
| Canary Trail Events Ltd | Arts & recreation | 2018 |