| Bizpal Solutions Limited | Administrative & support | 2022 |
| Bizplates Limited | Wholesale & retail | 2010 |
| Bizzlogics Limited | Information & communication | 2014 |
| BJS Holdings Limited | Financial services | 2017 |
| Bl&Cw Ltd | Professional & scientific | 2024 |
| Black CAB Limited | Transport & logistics | 2022 |
| Black Cat Corporation Limited | Real estate | 1981 |
| Black Horse Mark Limited | Real estate | 2024 |
| Black Label Group Ltd | Health & social care | 2017 |
| Black Line Growth Limited | Other services | 2025 |
| Black Lion Chauffeurs Ltd | Transport & logistics | 2023 |
| Black Orchid Services Limited | Real estate | 2023 |
| Black Rooster Limited | Manufacturing | 2013 |
| Black Sea Ltd | Wholesale & retail | 2017 |
| Blackamoor Films Ltd | Arts & recreation | 2022 |
| Blackbelt Chiroh Ltd | Health & social care | 2025 |
| Blackberry Hill Limited | Health & social care | 2004 |
| Blackframe Studios Ltd | Information & communication | 2026 |
| Blackline EMS London Ltd | Arts & recreation | 2018 |
| Blackstone Construction Consultants Ltd. | Construction | 2016 |
| Blackstone Tutors Limited | Education | 2013 |
| Blades Transport & Logistics LLP | | 2025 |
| Blaiz Limited | Wholesale & retail | 2015 |
| Blak Rock Ltd | Real estate | 2012 |
| Blakeney Bolt Holes Limited | Real estate | 2004 |
| Blanco Brownes Limited | Administrative & support | 2013 |
| BLC Music Limited | Arts & recreation | 2016 |
| Bleak Apparel Limited | Wholesale & retail | 2017 |
| Blelk Services Ltd | Construction | 2025 |
| Bleman International Limited | Administrative & support | 2015 |
| Bleman Property Group Ltd | Real estate | 2022 |
| Blend Studios Ltd | Arts & recreation | 2006 |
| Blendart Limited | Arts & recreation | 1993 |
| Blended Homes Ltd | Real estate | 2024 |
| Blenheim Road Developments Limited | Real estate | 2018 |
| Bleriot & Catherall Holdings Ltd | Financial services | 2020 |
| Bleriot Construction Limited | Construction | 1993 |
| Bleriot Holdings Limited | Real estate | 2000 |
| Blessed With Love Ltd | Arts & recreation | 2017 |
| Bletchley Consultants Limited | Information & communication | 2016 |
| Blick & Co. LLP | | 2022 |
| Blink Optics Limited | Health & social care | 2017 |
| BLK Investments Group Limited | Professional & scientific | 2020 |
| Blk.Fx Ltd | Financial services | 2021 |
| Blknomics Ltd | Wholesale & retail | 2026 |
| BLOCK9 Display Limited | Manufacturing | 2011 |
| Blood Moon Ltd | Information & communication | 2012 |
| Bloom Roofing Limited | Construction | 2019 |
| Bloomfloor Ltd | Professional & scientific | 2023 |
| Blooming Productions Limited | Arts & recreation | 1990 |
| BLR21 Cleaning Services Limited | Administrative & support | 2021 |
| Blrn Limited | Real estate | 2016 |
| BLS Forest Hill Limited | Real estate | 2024 |
| BLS TV & Film Construction Limited | Professional & scientific | 2015 |
| Bludiam Ltd | Wholesale & retail | 2025 |
| Blue Abacus Consulting Limited | Professional & scientific | 2020 |
| Blue Alpine Limited | Real estate | 2014 |
| Blue Alpine Partners Limited | Real estate | 2018 |
| Blue Chip 81 Ltd | Construction | 2022 |
| Blue Chip Cleaning & Support Services Ltd | Other services | 2011 |
| Blue Cross Care Limited | Administrative & support | 2010 |
| Blue Design & Create Ltd | Professional & scientific | 2018 |
| Blue Door Management Ltd | Professional & scientific | 2023 |
| Blue EYE Consultants Ltd | Real estate | 2016 |
| Blue Goose Interiors Limited | Other services | 2010 |
| Blue Harbour 2 Limited | Other services | 2006 |
| Blue Harbour 3 Limited | Other services | 2006 |
| Blue Harbour Limited | Other services | 1987 |
| Blue Horizon Healthcare Ltd | Real estate | 2019 |
| Blue Magpie London Ltd | Professional & scientific | 2018 |
| Blue Skies Addiction Centre Ltd | Health & social care | 2013 |
| Blue Sky Tipis Ltd | Other services | 2019 |
| Blue Star Construction Management Ltd | Professional & scientific | 2023 |
| Blue Star Roofing Ltd | Construction | 2023 |
| Blue Water Renewables Ltd | Construction | 2022 |
| Blue Water Systems Limited | Construction | 2012 |
| Bluespin Ltd | Real estate | 2022 |
| Bluespur Properties Ltd | Real estate | 2020 |
| Bluestone ARM Limited | Professional & scientific | 2009 |
| Bluestone Landscapes Ltd | Construction | 2018 |
| Bluestreams Limited | Wholesale & retail | 2005 |
| Blume Floristry Limited | Other services | 2020 |
| Blyths Wharf Residents' Association Limited | Households | 1995 |
| BM Auction Property Limited | Real estate | 2015 |
| BMA Property Developers Limited | Construction | 2019 |
| BMS Maintenance Services Ltd | Construction | 2016 |
| BMS Towing Ltd | Transport & logistics | 2014 |
| BNI Chipping Ltd | Other services | 2022 |
| Bnkbl Ltd | Information & communication | 2007 |
| Boatmans House Limited | Real estate | 2018 |
| Bobbins Pictures Ltd | Professional & scientific | 2023 |
| Bobby Change Limited | Hospitality | 2001 |
| Bobby's Electrical Services Ltd | Construction | 2021 |
| BOBBY4U2BUILDING Ltd | Construction | 2015 |
| Bobroff Real Estate LLP | | 2017 |
| Bobwish Ltd | Construction | 2015 |
| Boca Trans Ltd | Transport & logistics | 2023 |
| Bocca Consulting Ltd | Construction | 2010 |
| BOD Beauty Ltd | Wholesale & retail | 2018 |
| Bodhicitta Lifeworks Ltd | Professional & scientific | 2018 |