| Balcony Limited | Professional & scientific | 2017 |
| Balderton Aviation Holdings Limited | Financial services | 2005 |
| Baldock Management Company Ltd | Real estate | 2025 |
| Balfour House Management Limited | Real estate | 2003 |
| Balfour House Properties Limited | Real estate | 2006 |
| Baljinder Singh Construction Ltd | Construction | 2025 |
| Baljit SINGH2 Ltd | Construction | 2021 |
| Balkanrewards Limited | Wholesale & retail | 2026 |
| Ball Beverage Packaging Holdings UK Limited | Professional & scientific | 1987 |
| Ball Beverage Packaging UK Ltd | Manufacturing | 1924 |
| Ball UK Acquisition Limited | Financial services | 2015 |
| Ballu Driver Ltd | Transport & logistics | 2024 |
| Ballylads Global Limited | Transport & logistics | 2025 |
| Ballyseede 2000 Consulting Ltd | Professional & scientific | 2016 |
| Balmo Holdings Limited | Construction | 2018 |
| Balmo Homes Limited | Construction | 2018 |
| Balmo Properties Limited | Real estate | 2013 |
| Baloch Holdings (UK) Limited | Financial services | 2017 |
| Balti Village Ltd | Hospitality | 2013 |
| Baltic Sun Ltd | Transport & logistics | 2015 |
| Baltoro Crystals Ltd | Wholesale & retail | 2026 |
| BAM3 Ltd | Other services | 2024 |
| Bambaji Faal Ltd | Transport & logistics | 2018 |
| Bambini Montessori Childcare Limited | Health & social care | 2022 |
| Bamboo House 1668 Ltd | Hospitality | 2026 |
| Bami's Complete Care Ltd | Health & social care | 2021 |
| Bampton Properties Limited | Real estate | 2023 |
| Bampton Trading Limited | Wholesale & retail | 2021 |
| Bamrah Construction Limited | Construction | 2025 |
| Bamsy Rail Limited | Construction | 2014 |
| Bamsy Yard Ltd | Wholesale & retail | 2025 |
| Bancos Ltd | Extraterritorial | 2005 |
| Bandi Investment Ltd | Real estate | 2021 |
| Bandon Cleaning Company Limited | Administrative & support | 2007 |
| Bang-On Roofing Limited | Construction | 2026 |
| Bangarh Limited | Administrative & support | 2026 |
| Bangla Bazar Direct Ltd | Wholesale & retail | 2017 |
| Bangla Halal Meat Limited | Wholesale & retail | 2025 |
| Bangla Store Limited | Wholesale & retail | 2011 |
| Bangleflame Ltd | Construction | 2021 |
| Bankai Ltd | Wholesale & retail | 2025 |
| Banner Electrical Solutions Ltd | Construction | 2024 |
| Bano Medical Ltd | Health & social care | 2020 |
| BAO G'S Builders Limited | Construction | 2023 |
| Bapa's Meals Community Interest Company | Wholesale & retail | 2021 |
| Bar Azita (Hitchin) Limited | Hospitality | 2015 |
| Bar Azita Limited | Hospitality | 2009 |
| Bar Coffee Lounge Parllaku Ltd | Hospitality | 2022 |
| Barak Technology Ltd | Administrative & support | 2019 |
| Barakah Advisory and Accountancy Services Limited | Professional & scientific | 2024 |
| Barakah Events Limited | Hospitality | 2025 |
| Barakah Maintenance Ltd | Construction | 2024 |
| Barakah Treasure Ltd | Wholesale & retail | 2025 |
| Barbara Stawiarska Transport Limited | Transport & logistics | 2024 |
| Barber Inc Limited | Other services | 2022 |
| Barber Station Luton Ltd | Other services | 2025 |
| Barberbox Limited | Other services | 2018 |
| Barclay Properties Limited | Real estate | 2005 |
| Bard Street Limited | Real estate | 1987 |
| Bardell Pearce Limited | Professional & scientific | 2022 |
| Bardman Properties Ltd | Real estate | 2025 |
| Bare Skin Laser and Skin Clinic Ltd | Other services | 2025 |
| Barford Brothers Limited | Other services | 1948 |
| Bargain House Ltd | Wholesale & retail | 2025 |
| Baristerslearner Ltd | Wholesale & retail | 2025 |
| Barkat Roofings and Interior Designs Limited | Construction | 2024 |
| Barker Grant Consulting Limited | Administrative & support | 2018 |
| Barking Premium Cars Ltd | Transport & logistics | 2019 |
| Barlarry Limited | Administrative & support | 2022 |
| Barliner Doner Kebab Limited | Hospitality | 2022 |
| Barner Properties Limited | Real estate | 2018 |
| Barnfield Enterprise Ltd | Hospitality | 2022 |
| Barnsdale Close RTM Company Limited | Households | 2014 |
| Barnston Translations Limited | Professional & scientific | 2023 |
| Barnyardmotorhouse Ltd | Wholesale & retail | 2025 |
| Baron VON Rogie Ltd | Administrative & support | 2014 |
| Baronu Construction Ltd | Construction | 2017 |
| Barq Global Limited | Wholesale & retail | 2025 |
| Barr's Big Bang's Limited | Arts & recreation | 2023 |
| Barraq UK Ltd | Wholesale & retail | 2025 |
| Barry Bolton Windows Limited | Construction | 2001 |
| Barry Figg Tennis Ltd | Education | 2025 |
| Barrypak Limited | Wholesale & retail | 2024 |
| Bart Carpentry & Maintenance Ltd | Manufacturing | 2025 |
| Bart-Phill Ltd | Wholesale & retail | 2014 |
| Bartham Press (Watford) Limited | Manufacturing | 1984 |
| Bartoc Limited | Health & social care | 2022 |
| Barton Road 1961 Limited | Extraterritorial | 2014 |
| Barton Vale Management Company Limited | Households | 2007 |
| Barton Van Rental Ltd | Administrative & support | 2022 |
| BAS Heating and Plumbing Services Ltd | Construction | 2025 |
| BAS Hire Ltd | Transport & logistics | 2026 |
| Basbaydar Legal Ltd | Professional & scientific | 2024 |
| Basby Limited | Health & social care | 2019 |
| Bascan Ltd | Construction | 2024 |
| Baseera Group Finance Limited | Financial services | 2025 |
| Baseform Ltd | Construction | 2012 |
| Baseline Designs Limited | Information & communication | 1998 |
| Basemath Limited | Information & communication | 2012 |
| Basement Builders Limited | Wholesale & retail | 2007 |