| Blackbird Homes (Rosemary Road) Limited | Construction | 2019 |
| Blackfusion UK Ltd | Information & communication | 2024 |
| Blackhost Ltd | Information & communication | 2024 |
| Blacklock & Company Ltd | Real estate | 2014 |
| Blackmore Windows and Doors Ltd | Manufacturing | 2022 |
| Blackstone 27 LLP | | 2021 |
| Blackthornsecurity Limited | Administrative & support | 2022 |
| Blackwater Mill Limited | Health & social care | 2012 |
| Blackways BR Limited | Wholesale & retail | 2025 |
| Blacky's Kitchen Ltd | Manufacturing | 2024 |
| Blahaj Secretaries Ltd | Professional & scientific | 2023 |
| Blahzay Media Ltd | Information & communication | 2010 |
| Blair Court Management Limited | Households | 2024 |
| Blake & Associates Limited | Professional & scientific | 2021 |
| Blake & Sons (Gosport) Limited | Professional & scientific | 1897 |
| Blakerock Limited | Real estate | 1999 |
| Blakeway & Blakeway Limited | Real estate | 2011 |
| Blandford Capital Advisor Limited | Professional & scientific | 2022 |
| Blandford Capital LLP | | 2018 |
| Blandford Forum Limited | Construction | 2008 |
| Blandford Rise Management Company Ltd | Households | 2019 |
| Blandford Road Ltd | Hospitality | 2020 |
| Blandford Road Residents Association Limited | Households | 1994 |
| Blandford RS Limited | Financial services | 2022 |
| Blastbox Games Ltd | Information & communication | 2023 |
| Blastworx (Holdings) Limited | Financial services | 2023 |
| Blastworx Limited | Construction | 2007 |
| Blazin Vapes Ltd | Wholesale & retail | 2022 |
| Bleach Limited | Other services | 2018 |
| Bleg Consulting Ltd | Professional & scientific | 2023 |
| Blendai Limited | Information & communication | 2024 |
| Blessing’S Beauty Ltd | Wholesale & retail | 2025 |
| Blind Chance Productions Ltd | Information & communication | 2020 |
| Blindshark Ltd | Information & communication | 2024 |
| Blissdata Ltd | Information & communication | 2021 |
| Blizzard PAY Ltd | Administrative & support | 2023 |
| Blockchain Investments Ltd | Information & communication | 2019 |
| Blockchain, Booty and BHP Ltd | Information & communication | 2023 |
| Blogwise Ltd | Information & communication | 2023 |
| Blokest Ltd | Information & communication | 2023 |
| Bloki Partners Ltd | Professional & scientific | 2023 |
| Blomsma Holdings Limited | Wholesale & retail | 2023 |
| Bloom Carehome Ltd | Financial services | 2026 |
| Blooms and Broth Flowers and Noodles Ltd | Wholesale & retail | 2026 |
| Bloor Civil Engineering Limited | Construction | 2015 |
| Blossom Dental Ltd | Health & social care | 2024 |
| Blossom Flower Threads Ltd | Wholesale & retail | 2025 |
| Blossom Hill Holdings Ltd | Real estate | 2019 |
| Blossom Hill Homes Ltd | Construction | 2016 |
| Blossom Hill Investments Ltd | Construction | 2019 |
| Blossom Hill Ltd | Extraterritorial | 2022 |
| Blossom Point Ltd | Administrative & support | 2023 |
| Blow White Ltd | Wholesale & retail | 2019 |
| BLR People Limited | Administrative & support | 2023 |
| Bltt UK Limited | Wholesale & retail | 2019 |
| Bltw Care Holdings Ltd | Professional & scientific | 2023 |
| Bltw Care Ltd | Health & social care | 2021 |
| BLU Cumulus Ltd | Other services | 2014 |
| BLU Sky Corporation Ltd | Wholesale & retail | 2025 |
| Blubrik Limited | Real estate | 2017 |
| Blue Ball Consultancy Limited | Professional & scientific | 2022 |
| Blue Ball Developments Limited | Real estate | 2016 |
| Blue Ball Holdings Limited | Real estate | 2015 |
| Blue Boss Ltd | Wholesale & retail | 2022 |
| Blue Chimp Limited | Information & communication | 2014 |
| Blue Crown Trading Limited | Wholesale & retail | 2025 |
| Blue Diamond Car Wash Ltd | Wholesale & retail | 2023 |
| Blue Diamond Hot TUB Care Ltd | Transport & logistics | 2025 |
| Blue Dolphin Consulting Limited | Professional & scientific | 2001 |
| Blue Drop Studio Limited | Information & communication | 2015 |
| Blue Fish Design Solutions Ltd | Professional & scientific | 2008 |
| Blue Flag Developments Limited | Real estate | 2012 |
| Blue Forest Real Estate Ltd | Real estate | 2022 |
| Blue Froth Ltd | Wholesale & retail | 2021 |
| Blue Gower 2 Limited | Financial services | 2022 |
| Blue Label Wealth Management Limited | Financial services | 2015 |
| Blue Lagoon ( Southern ) Ltd | Administrative & support | 2019 |
| Blue Lagoon (Services) Ltd | Manufacturing | 2021 |
| Blue Mimosa Ltd | Real estate | 2011 |
| Blue Mode Academy Ltd | Education | 2025 |
| Blue Ocean Homes Ltd | Real estate | 2018 |
| Blue Parrot Group Limited | Wholesale & retail | 2018 |
| Blue Pebble Finance Limited | Financial services | 2006 |
| Blue Pebble Property Ltd | Real estate | 2020 |
| Blue Planet Environmental Limited | Professional & scientific | 2018 |
| Blue Poppy Threads Ltd | Wholesale & retail | 2026 |
| Blue Roof Professional Services Limited | Professional & scientific | 2019 |
| Blue Service Solutions Limited | Construction | 2010 |
| Blue Skies Aviation Ltd | Transport & logistics | 2024 |
| Blue Sky Activities Limited | Administrative & support | 2022 |
| Blue Sky Adventure Limited | Administrative & support | 2014 |
| Blue Sky Anaesthetics Limited | Health & social care | 2017 |
| Blue Sky Financial Planning Limited | Financial services | 2002 |
| Blue Star Eyewear Ltd | Professional & scientific | 2025 |
| Blue Water Properties Ltd | Real estate | 2013 |
| Blue Wheat Co., Ltd | Professional & scientific | 2019 |
| Bluebell Meadow Limited | Hospitality | 2017 |
| Bluebell Medical Services Ltd | Health & social care | 2017 |
| Bluebell Valeting Ltd | Administrative & support | 2020 |
| Bluebird Security Limited | Construction | 2003 |