| Blagrave Street Ventures Limited | Financial services | 2014 |
| Blagrove D W Ltd | Real estate | 2024 |
| Blaidhurst Limited | Real estate | 2007 |
| Blakemore Insight & Learning Limited | Education | 2012 |
| Blakes Quay Management Company Limited | Households | 2002 |
| Blandy & Blandy LLP | | 2009 |
| Blandy Enterprises Ltd | Information & communication | 2024 |
| Blane Consultancy Ltd | Professional & scientific | 2011 |
| Blank Spce Ltd | Wholesale & retail | 2021 |
| Blatchley Consulting Ltd | Administrative & support | 2024 |
| Blazeboard Limited | Extraterritorial | 2019 |
| Bleinheim Vision Limited | Health & social care | 2022 |
| Blend Marketing Limited | Administrative & support | 2010 |
| Blended Wellbeing Limited | Other services | 2026 |
| Blenheim & Chester Developments Limited | Construction | 2014 |
| Blenheim Capital Services Limited | Financial services | 2019 |
| Blenheim Constructions Group Ltd | Construction | 2025 |
| Blenheim Space UK Limited | Information & communication | 2016 |
| Blenheim Terrace RTM Company Limited | Real estate | 2017 |
| Blessed Hands Support Limited | Health & social care | 2022 |
| Blessed KIN Trading Co Ltd | Real estate | 2022 |
| Blessed Talk Ltd | Health & social care | 2023 |
| Bletchley Bidco Limited | Financial services | 2020 |
| Bletchley EBT & Nominee Limited | Professional & scientific | 2020 |
| Bletchley Midco Limited | Financial services | 2020 |
| Bletchley Topco Limited | Financial services | 2020 |
| Blewbury Bread Ltd | Manufacturing | 2023 |
| Blewusi Ltd | Wholesale & retail | 2023 |
| Blick Tech Ltd | Professional & scientific | 2012 |
| Blind Children UK | Health & social care | 1995 |
| Blind Children UK (Trading) Limited | Extraterritorial | 2001 |
| Bling Bling Investment Limited | Real estate | 2021 |
| Blink UP Limited | Professional & scientific | 2026 |
| Blinkhorns Audio Visual Limited | Wholesale & retail | 2008 |
| Blip (Reading Central) Ltd | Hospitality | 2026 |
| Blip (Reading) Ltd | Hospitality | 2025 |
| Bliss Family Homes Limited | Real estate | 2022 |
| Bliss Mobile Car Wash Limited | Administrative & support | 2024 |
| Bliss School Transport Limited | Transport & logistics | 2025 |
| BLISSCARS247 Ltd | Transport & logistics | 2018 |
| Blissful Care Limited | Health & social care | 2013 |
| Blissful Healthcare International Limited | Health & social care | 2018 |
| Blissful Healthcare Limited | Health & social care | 2025 |
| Blissful Living Limited | Health & social care | 2014 |
| Blissful Physio Therapy Ltd | Health & social care | 2025 |
| Blissful Technologies Ltd | Information & communication | 2025 |
| Blisworth Solar Limited | Energy | 2015 |
| Bloc GEL Ltd | Professional & scientific | 2021 |
| Block MGT Limited | Real estate | 2024 |
| Blockchain Imperative Limited | Information & communication | 2018 |
| Blomac Limited | Real estate | 1984 |
| Bloom Health Hospitals Ltd | Health & social care | 2024 |
| Bloom Homes Limited | Real estate | 2021 |
| Bloombrand Fusions Limited | Real estate | 2009 |
| Bloomfield Estate Management Ltd | Real estate | 2026 |
| Bloomfield Hatch Stables M.C. Limited | Households | 1997 |
| Bloomfield Homes Ltd | Construction | 2024 |
| Bloomfield Investments Ltd | Real estate | 2025 |
| Blooming Ashley’S Limited | Wholesale & retail | 2020 |
| Bloomsbury Street Developments Limited Partnership | | 1989 |
| Blooners 2000 Limited | Extraterritorial | 2000 |
| Blosh Ltd | Manufacturing | 2024 |
| Blossomwoods Properties Limited | Real estate | 2026 |
| BLS Carpentry Limited | Construction | 2004 |
| BLU Fashion Ltd | Wholesale & retail | 2025 |
| BLU Property Maintenance Management Limited | Construction | 2019 |
| Blue Angel Care Limited | Health & social care | 2015 |
| Blue Array Ltd | Information & communication | 2015 |
| Blue Band IT Solutions Ltd | Information & communication | 2013 |
| Blue Bidco Limited | Financial services | 2018 |
| Blue Builders Ltd | Construction | 2017 |
| Blue Canvas Ltd | Real estate | 2023 |
| Blue Cedar Court Management Co Ltd | Households | 2021 |
| Blue Cloud Properties Limited | Real estate | 2023 |
| Blue Cloud Solutions Limited | Information & communication | 2019 |
| Blue Collar Club Limited | Wholesale & retail | 2024 |
| Blue Compass Consulting Limited | Professional & scientific | 2018 |
| Blue Daisy Marketing Solutions Limited | Administrative & support | 2022 |
| Blue Diamond Sustainable Investments Ltd | Other services | 2024 |
| Blue Dome Ltd | Information & communication | 2018 |
| Blue Door Group Ltd | Real estate | 2021 |
| Blue Eyes Trading L Limited | Wholesale & retail | 2025 |
| Blue Fern Homes Ltd | Construction | 2013 |
| Blue Fern Landscapes Ltd | Administrative & support | 2018 |
| Blue Fern Logistics Limited | Real estate | 2006 |
| Blue Files Ltd | Professional & scientific | 2013 |
| Blue Flame Consultants Limited | Professional & scientific | 2017 |
| Blue Gate Property Ltd | Real estate | 2025 |
| Blue Genius Limited | Information & communication | 2016 |
| Blue Grease Productions Limited | Information & communication | 2024 |
| Blue Grid Solutions Limited | Information & communication | 2018 |
| Blue Holdco Limited | Financial services | 2018 |
| Blue House Farm Solar Limited | Energy | 2015 |
| Blue Infusion Ltd | Information & communication | 2024 |
| Blue Key Developments Ltd | Construction | 2017 |
| Blue Key Residential Ltd | Real estate | 2018 |
| Blue Line Electrical Services Ltd | Construction | 2024 |
| Blue Marble Pictures Limited | Information & communication | 2015 |
| Blue Market Limited | Transport & logistics | 2018 |
| Blue Midco Limited | Financial services | 2018 |