| Bizalex Ltd | Construction | 2026 |
| Bizlink Real Estate UK Ltd | Real estate | 2025 |
| BJ Ferdous Ltd | Health & social care | 2023 |
| BJF Property Asset Management Ltd | Other services | 2018 |
| Bjjames Line Limited | Health & social care | 2021 |
| Bjnn Properties Ltd | Real estate | 2026 |
| BK & SA Food Ltd | Hospitality | 2022 |
| BK Elite Estates Ltd | Wholesale & retail | 2024 |
| BK Social Care Limited | Health & social care | 2020 |
| BK7 Builders Limited | Construction | 2024 |
| BKA ( Essex ) Limited | Hospitality | 2023 |
| Bkure Ltd | Information & communication | 2024 |
| BL Capital Limited | Real estate | 2017 |
| BLA Global Limited | Transport & logistics | 2012 |
| Black Diamond Tattoos Limited | Arts & recreation | 2018 |
| Black Ice Academy Limited | Arts & recreation | 2019 |
| Black Mango Consultancy Ltd | Information & communication | 2023 |
| Black Ocean Solutions Ltd | Wholesale & retail | 2025 |
| Black Phoenix Tattoo Ltd | Other services | 2025 |
| Black Rock Financial Ltd | Financial services | 2012 |
| Black Steel Ltd | Wholesale & retail | 2025 |
| Black Sun Studios Ltd | Manufacturing | 2020 |
| Black Sunrise Ltd | Wholesale & retail | 2018 |
| Black Swan Consultancy Services Ltd | Professional & scientific | 2021 |
| Black TIE Private Ltd | Administrative & support | 2026 |
| Black Webster Limited | Wholesale & retail | 2025 |
| Blackbridge Holdings Limited | Real estate | 2026 |
| Blackfinch Films Ltd | Arts & recreation | 2019 |
| Blackforge Diesel Engines Ltd | Wholesale & retail | 2026 |
| Blackhorse Holdings Limited | Other services | 2009 |
| Blackmoon Design Ltd | Arts & recreation | 2021 |
| Blackrock Install Limited | Construction | 2021 |
| Blackrose Property Service Limited | Households | 2025 |
| Blackstock Capital Developments Ltd | Real estate | 2014 |
| Blackstock Capital Estates Ltd | Real estate | 2014 |
| Blackstock Capital Properties Ltd | Real estate | 2014 |
| Blackstock Plumbing and Heating Ltd | Construction | 2014 |
| Blackstone Auto Centre Ltd | Wholesale & retail | 2026 |
| Blackstone Events Limited | Hospitality | 2014 |
| Blackstone Foods Limited | Manufacturing | 2021 |
| Blackstone Residential Management Ltd | Real estate | 2026 |
| Blacksummit Limited | Professional & scientific | 2025 |
| Blackwall UK Ltd | Real estate | 2024 |
| Blackwell House Farm Ltd | Manufacturing | 2026 |
| Blade Protection Ltd | Manufacturing | 2023 |
| Blaen Cefn Holdings Limited | Financial services | 2021 |
| Blak Diamond Social Care Limited | Health & social care | 2009 |
| Blake Dixon Ltd | Information & communication | 2016 |
| Blake's Doggy Daycare Ltd | Wholesale & retail | 2025 |
| Blanchard French Polishers Limited | Construction | 2008 |
| Blanchard Properties Limited | Real estate | 2022 |
| Blanco Builders Ltd | Construction | 2026 |
| Blank Page Digital Ltd | Information & communication | 2026 |
| Blast Bubble Ltd | Hospitality | 2017 |
| BLB Advertising Limited | Other services | 2013 |
| BLD Ltd | Financial services | 2019 |
| Bleakman Bodyworks Limited | Manufacturing | 2025 |
| Blees Gold Ltd | Manufacturing | 2015 |
| Blenman Ltd | Real estate | 2025 |
| Blenman Property Ltd. | Households | 2021 |
| Blero Ltd | Construction | 2017 |
| Bless Gilbert Limited | Wholesale & retail | 2026 |
| Blessday Services Limited | Real estate | 2017 |
| Blessed Hub Care Ltd | Health & social care | 2022 |
| Blessed Muslim UK Ltd | Information & communication | 2021 |
| Blinds Aligned Limited | Other services | 2022 |
| Blink Distribution Ltd | Information & communication | 2024 |
| Bliss Care & Stays Ltd | Hospitality | 2026 |
| Bliss Luxury Travel Limited | Administrative & support | 2023 |
| Blissful Arches Ltd | Arts & recreation | 2026 |
| Block C Dellow Close Limited | Real estate | 2003 |
| Blockchain Mint Private Clients Limited | Real estate | 2018 |
| Bloom Nature Ltd | Health & social care | 2024 |
| Bloom Ventures Limited | Professional & scientific | 2013 |
| Bloom's Cafe Ltd | Hospitality | 2025 |
| Blooming Birds Nurseries Limited | Financial services | 2025 |
| Blooming Camellia Limited | Wholesale & retail | 2022 |
| Blooming Families Ltd | Education | 2024 |
| Blooming Parenting Limited | Extraterritorial | 2016 |
| Blooming Treasures CIC | Health & social care | 2025 |
| Bloomsbury Cafe Limited | Hospitality | 2019 |
| Blossom Care Support Limited | Health & social care | 2025 |
| Blossom Key Lettings Limited | Real estate | 2025 |
| Blossom Lodge Limited | Professional & scientific | 2023 |
| Blossom Therapies Ltd | Health & social care | 2025 |
| Blossomade Ltd | Hospitality | 2014 |
| Blossoms Montessori Children's House Limited | Health & social care | 2023 |
| Blri Services Solution Limited | Construction | 2023 |
| Blsa. Ltd | Other services | 2024 |
| Bltk Consulting Limited | Professional & scientific | 2013 |
| BLU Sky Day Limited | Professional & scientific | 2024 |
| Blue Bridge Care Limited | Health & social care | 2025 |
| Blue Building Services Ltd | Construction | 2021 |
| Blue Chilli Events Hire Ltd | Other services | 2023 |
| Blue Clay Land Limited | Construction | 2025 |
| Blue Diamond Shopfront & Shutter Ltd | Construction | 2019 |
| Blue Door Solutions Limited | Administrative & support | 2015 |
| Blue Feather Films Limited | Information & communication | 2021 |
| Blue Gold Promotions Ltd | Arts & recreation | 2023 |
| Blue Hammer Building Services Ltd | Construction | 2022 |