| Bkri Emea Limited | Professional & scientific | 2021 |
| Bksr Properties Ltd | Real estate | 2026 |
| BL Property Management Ltd | Real estate | 2017 |
| Black Belt Therapeutics Limited | Professional & scientific | 2018 |
| Black Cactus Consulting Limited | Professional & scientific | 2023 |
| Black Cat OPS Limited | Information & communication | 2026 |
| Black Dakota Limited | Information & communication | 2018 |
| Black Line Group Limited | Professional & scientific | 2023 |
| Black Lodge Consulting Limited | Information & communication | 2023 |
| Blackbird Yard NOM2 Limited | Financial services | 2023 |
| Blackbirdai Limited | Information & communication | 2023 |
| Blackcroft Properties Limited | Real estate | 2016 |
| Blackcross Consulting Limited | Administrative & support | 2022 |
| Blackfinbio Limited | Professional & scientific | 2023 |
| Blackheath Village Community Limited | Professional & scientific | 2025 |
| Blackjam Limited | Professional & scientific | 2018 |
| Blacks Aesthetics (Hale) Ltd | Wholesale & retail | 2024 |
| Blackshaw Tax Ltd | Professional & scientific | 2016 |
| Blackstar Consultants Limited | Information & communication | 2010 |
| Blackstone Properties (Hale) Limited | Real estate | 2025 |
| Blackstone Solicitors Limited | Professional & scientific | 2010 |
| Blackwood Engineering Services Limited | Professional & scientific | 2019 |
| Blade Acquisition Limited | Financial services | 2018 |
| Blair Shepherd Accountants Limited | Professional & scientific | 2003 |
| Blakeholme Limited | Wholesale & retail | 2002 |
| Blanco Electric Limited | Construction | 2020 |
| Bland Holdings Limited | Financial services | 2025 |
| Blessed Beauty by Cherelle Ltd | Other services | 2026 |
| Blessing Properties Limited | Real estate | 1984 |
| Bleu Corporate Ltd | Wholesale & retail | 2023 |
| Blicx Ltd | Professional & scientific | 2009 |
| Bliply Limited | Information & communication | 2026 |
| Bloc Group Hospitality Ltd | Hospitality | 2026 |
| Blood Red Moon Limited | Administrative & support | 2018 |
| Bloom Procurement Services Ltd | Professional & scientific | 2012 |
| Bloomin Gardens Limited | Administrative & support | 2020 |
| Bloomsbury Computing Solutions Ltd | Information & communication | 1997 |
| Bloomsbury Consulting Limited | Administrative & support | 2022 |
| Blossom Care Private Limited | Health & social care | 2022 |
| Bludisplay Limited | Wholesale & retail | 2017 |
| Blue 2 Solutions Limited | Energy | 2017 |
| Blue Ball Inn Limited | Hospitality | 2019 |
| Blue Bay Homes (Clifftops) Limited | Construction | 2014 |
| Blue BEE Controls Ltd | Professional & scientific | 2018 |
| Blue Dafodil Limited | Real estate | 2024 |
| Blue Eagle FD Services Ltd | Professional & scientific | 2013 |
| Blue Edge Properties Limited | Real estate | 2020 |
| Blue FOX Trade Ltd | Construction | 2025 |
| Blue Light Dent Holding Ltd | Financial services | 2019 |
| Blue Mountain Property Ltd | Construction | 2022 |
| Blue Ocean King Limited | Hospitality | 2019 |
| Blue Pass Training Limited | Education | 2026 |
| Blue Sky Foods Ltd | Hospitality | 2018 |
| Blue Sound Limited | Other services | 2008 |
| Blue Terracotta Consulting Ltd | Professional & scientific | 2023 |
| Blue Umbrella Risk Management Limited | Financial services | 2016 |
| Bluebelleuk Ltd | Wholesale & retail | 2023 |
| Blueberry Designs (Cheshire) Ltd | Manufacturing | 2020 |
| Bluecar Limited | Professional & scientific | 2019 |
| Bluecat Networks Europe Limited | Information & communication | 2007 |
| Bluecroft Brokers Limited | Financial services | 2019 |
| Bluecroft Finance Limited | Financial services | 2022 |
| Bluecroft Finance Subco 1 Limited | Financial services | 2024 |
| Bluecroft Finance Subco 2 Limited | Financial services | 2024 |
| Bluecroft Finance Subco 3 Limited | Financial services | 2024 |
| Bluecroft Finance Subco 4 Limited | Financial services | 2024 |
| Bluecroft Finance Subco 5 Limited | Financial services | 2025 |
| Bluecroft Finance Subco 6 Limited | Financial services | 2025 |
| Bluecroft Finance Subco 7 Limited | Financial services | 2025 |
| Bluecroft Finance Subco 8 Limited | Financial services | 2025 |
| Bluecroft Holdings Limited | Financial services | 2025 |
| Bluecroft Traders Limited | Wholesale & retail | 2019 |
| Blueground Holdings Limited | Professional & scientific | 2015 |
| Bluemantle Operations Limited | Construction | 2026 |
| Bluerock Limited | Professional & scientific | 2018 |
| Blundells Property Services Limited | Professional & scientific | 2007 |
| Blush Healthcare Ltd | Wholesale & retail | 2022 |
| Blushell Limited | Professional & scientific | 2024 |
| Bluwasp Ltd | Information & communication | 2016 |
| BM NOM1 Limited | Professional & scientific | 2021 |
| BM NOM2 Limited | Professional & scientific | 2021 |
| Bmma Altrincham Ltd | Education | 2024 |
| BN Consultation Ltd | Professional & scientific | 2022 |
| BN Trust Ltd | Real estate | 2022 |
| BN61 Limited | Professional & scientific | 2025 |
| Bnker Ltd | Transport & logistics | 2024 |
| Bnor Limited | Health & social care | 2024 |
| BOA Artistic Team Ltd | Other services | 2019 |
| Boanerges Limited | Extraterritorial | 1999 |
| Boatstem Limited | Professional & scientific | 1999 |
| BOB W Technologies UK Limited | Hospitality | 2020 |
| Bobby London Limited | Administrative & support | 2025 |
| Bobby MAX Security Limited | Professional & scientific | 2024 |
| Bobsmith Ltd | Professional & scientific | 2026 |
| Bodep Consulting Services Limited | Information & communication | 2022 |
| Bodhi Holdings Ltd | Financial services | 2025 |
| Bodika Rocks Limited | Manufacturing | 2019 |
| Bogdan Dogaru Limited | Professional & scientific | 2024 |
| BOILER-M8 Limited | Wholesale & retail | 2019 |
| Boing Acquisitions Limited | Wholesale & retail | 2014 |