| Blue Dragon (Hillingdon) Limited | Other services | 1926 |
| Blue Flame Heating & Plumbing Care Ltd | Construction | 2025 |
| Blue Haulers Inc. Ltd | Transport & logistics | 2023 |
| Blue Lion Studios Ltd | Transport & logistics | 2024 |
| Blue Magnet Limited | Professional & scientific | 2012 |
| Blue Ocean 444 Ltd | Real estate | 2021 |
| Blue Pluto Limited | Hospitality | 2025 |
| Blue Saffron Indian Takeaway Ltd | Hospitality | 2019 |
| Blue Sea Trading Company Limited | Wholesale & retail | 2009 |
| Blue Sky Procurement Limited | Professional & scientific | 2025 |
| Bluebead Architects Ltd. | Professional & scientific | 2022 |
| Bluefox London Ltd | Construction | 2018 |
| Bluenight Trading Ltd | Wholesale & retail | 2021 |
| Bluenile Services Ltd | Professional & scientific | 2025 |
| Blueride Ltd | Transport & logistics | 2019 |
| BM Sports Limited | Arts & recreation | 2024 |
| BME Holdings 1 Limited | Professional & scientific | 2024 |
| BN YT Ltd | Information & communication | 2025 |
| BOB Crowley Property Limited | Real estate | 2024 |
| Bocioaca Decorating Ltd | Construction | 2026 |
| Bocioaca Ltd | Construction | 2023 |
| Bockowskibuilder Ltd | Construction | 2022 |
| Body Biophysics Ltd | Health & social care | 2021 |
| Body Temple UXB Ltd | Other services | 2014 |
| Bodyflexldn Ltd | Other services | 2025 |
| Boerbok Ltd | Professional & scientific | 2017 |
| Boldace Limited | Other services | 1992 |
| Boldbrand Limited | Transport & logistics | 2006 |
| Boldgate Commercial Services Limited | Manufacturing | 2006 |
| Boldgate Limited | Manufacturing | 2007 |
| Bolina Limited | Financial services | 2020 |
| Bombay Tiimes Ltd | Hospitality | 2018 |
| BON Voyage Limited | Transport & logistics | 2012 |
| Bonafide Design Ltd | Professional & scientific | 2015 |
| Bonaiyu Health UK Ltd | Manufacturing | 2021 |
| Bone One Rigging Ltd | Arts & recreation | 2018 |
| Bonnie & Clyde Ltd | Administrative & support | 2025 |
| Bonnyleaf Limited | Wholesale & retail | 2020 |
| Bonshal Limited | Information & communication | 2025 |
| Book a Lorry Limited | Water & waste | 2020 |
| Book My Laundry Ltd | Other services | 2026 |
| Bookcash Trading Limited | Hospitality | 1994 |
| BOOKS4YOU Ltd | Wholesale & retail | 2026 |
| Boosted Power Limited | Administrative & support | 2025 |
| BOQ Consulting Limited | Real estate | 2024 |
| Borders Security Services Limited Limited | Financial services | 2022 |
| Bordery Limited | Professional & scientific | 2015 |
| Borthwicks Ltd | Real estate | 2007 |
| Bosch Automotive Service Solutions Ltd | Wholesale & retail | 1966 |
| Bosch Home Comfort Europe Finance Limited | Professional & scientific | 2015 |
| Bosch Home Comfort Europe Limited | Professional & scientific | 2015 |
| Bosch Home Comfort India Holding Limited | Professional & scientific | 2015 |
| Bosch Home Comfort UK (Jersey) Limited | Professional & scientific | 2015 |
| Bosch Home Comfort UK Holding Limited | Professional & scientific | 2015 |
| Bosch Home Comfort UK Investments Limited | Professional & scientific | 2015 |
| Bosch Home Comfort UK Technology Limited | Professional & scientific | 2015 |
| Bosch Home Comfort UK Waterlooville Limited | Professional & scientific | 2015 |
| Boscombe Food & Wine Ltd | Wholesale & retail | 2020 |
| Bosh Creative Services Limited | Professional & scientific | 2015 |
| Boston Creative Limited | Manufacturing | 2003 |
| Bostonsecuritygroup Ltd | Construction | 2026 |
| Bosworth Close Management Company Limited | Real estate | 2022 |
| Bothasig Logistics Services Ltd | Transport & logistics | 2026 |
| Botswana Community UK Ltd | Other services | 2018 |
| Bottling Great Britain Limited | Professional & scientific | 2002 |
| Bottling Holdings Europe Limited | Financial services | 2016 |
| Boulangerie DE Paris Limited | Manufacturing | 2007 |
| Bourne Financial Options Ltd | Financial services | 2022 |
| Bowdcrest Limited | Hospitality | 2017 |
| Bowerbird Studio Ltd | Manufacturing | 2026 |
| Bowmans Green Estate Management Limited | Households | 2015 |
| BOX2BOX Products Ltd | Wholesale & retail | 2017 |
| Boxer Wayfinder Logistics Ltd | Transport & logistics | 2026 |
| Boyn Hill Avenue (Freehold) Limited | Real estate | 2007 |
| Boyn Hill Avenue (Maidenhead) Limited | Real estate | 1985 |
| BP Electrical Ltd | Administrative & support | 2015 |
| Bpms Consultants Limited | Information & communication | 2024 |
| Brackenbury Property Management Ltd | Real estate | 2014 |
| Bradshaw Smith Ltd | Administrative & support | 2012 |
| Brainstem Tuition Ltd | Education | 2025 |
| Bramham Properties (HCT) Nine Ltd | Construction | 2021 |
| Branas Isaf (Ashfield House) Limited | Health & social care | 2006 |
| Branas Isaf (Bythnod & Hendre Llwyd) Limited | Health & social care | 2003 |
| Branas Isaf (Dewis Cyfarfod & Cysgod Cyfarfod) Limited | Health & social care | 2003 |
| Branas Isaf (Education Centre) Limited | Education | 2003 |
| Branas Isaf (Holdings) Limited | Professional & scientific | 2003 |
| Branas Isaf (Llyn Coed) Limited | Health & social care | 2003 |
| Branas Isaf Personal Development Centre Limited | Health & social care | 1999 |
| Branas UK One Limited | Real estate | 2026 |
| Branchwalkers Tree Surgery Ltd | Agriculture & fishing | 2015 |
| Brandquik Ltd | Transport & logistics | 2024 |
| Branislav Czako Ltd | Health & social care | 2018 |
| Branscombe House Management Company Limited | Households | 1996 |
| Brar Group Limited | Transport & logistics | 2024 |
| Brar Rental Ltd | Real estate | 2020 |
| Brasstof Limited | Other services | 2002 |
| Brastop Limited | Wholesale & retail | 2003 |
| Braveface Film Ltd | Information & communication | 2015 |
| Braveheart Investments Ltd | Real estate | 2005 |
| Braver Investment Group Limited | Financial services | 2020 |