| Britcart Bazaar Ltd | Wholesale & retail | 2025 |
| Britem Graphics Limited | Wholesale & retail | 2021 |
| British Diamond Wire DIE Company Limited | Manufacturing | 1925 |
| British HO Models Limited | Manufacturing | 2000 |
| British Mist Ltd | Wholesale & retail | 2026 |
| Britt Comms Ltd | Administrative & support | 2022 |
| Brittany Davids Ltd | Real estate | 2024 |
| Brixey Properties Limited | Real estate | 2021 |
| Brixey Road Management Company Limited | Households | 2020 |
| Brixey RTM Company Limited | Households | 2024 |
| BRL Cabling Ltd | Construction | 2025 |
| BRM Traders Ltd | Wholesale & retail | 2024 |
| Broadleaf Recruitment Limited | Administrative & support | 2013 |
| Broadstone Sports Cars Limited | Wholesale & retail | 2020 |
| Broadsworth Quarry Investments Ltd | Real estate | 2023 |
| Broadview Holdings (Poole) Limited | Financial services | 2024 |
| Broadview Shading Solutions Ltd | Wholesale & retail | 2013 |
| Broadview Vehicle Awnings Ltd | Wholesale & retail | 2013 |
| Broccoli Property Limited | Real estate | 2023 |
| Brokerbot Ltd | Professional & scientific | 2025 |
| Brooke Summer Adams Limited | Professional & scientific | 2021 |
| Brookes Bacon Limited | Manufacturing | 2000 |
| Brookland Associates Limited | Information & communication | 2008 |
| Brooklyn Poole Ltd | Hospitality | 2025 |
| Brookman Design Limited | Professional & scientific | 2009 |
| Brookmoor Builders Ltd | Construction | 2022 |
| Brooks Legal Ltd | Professional & scientific | 2022 |
| Brookskebbey Limited | Administrative & support | 2015 |
| Brooksmanage Ltd | Manufacturing | 2022 |
| Broom Engineering Services Limited | Professional & scientific | 2015 |
| Broomfield Wind Ltd | Energy | 2013 |
| Broomrigg Properties Limited | Households | 2002 |
| Brow Design Studio Limited | Health & social care | 2018 |
| Brown Booth Holdings Limited | Financial services | 2022 |
| Brown Booth Ltd | Information & communication | 2020 |
| Brown Homes Limited | Real estate | 2009 |
| Browne Services Limited | Information & communication | 2017 |
| Browning Fawkner Limited | Health & social care | 2018 |
| Brownsea Boats Ltd | Transport & logistics | 2026 |
| Brownsea Electrical Ltd | Construction | 2020 |
| Brownsea Island Cruises Limited | Transport & logistics | 1997 |
| Brownsea Island Ferries Limited | Transport & logistics | 1996 |
| Brownsea Island Holdings Limited | Financial services | 1967 |
| Brownsea Limited | Construction | 2007 |
| Brows by Sonia Ltd | Other services | 2023 |
| Brs-Systems Ltd | Professional & scientific | 2022 |
| Brtlane BR Limited | Wholesale & retail | 2025 |
| Bruce Mclaren Motor Racing Limited | Extraterritorial | 1975 |
| Brulex Holdings and Investments Ltd | Real estate | 2024 |
| Brunyee Carpentry Limited | Construction | 2007 |
| Brush Monroe Limited | Wholesale & retail | 2020 |
| Brwn Solutions Ltd | Wholesale & retail | 2026 |
| Bryan Builders Limited | Real estate | 2002 |
| Bryan Property Lettings and Management Ltd | Financial services | 2023 |
| Bryant Projects Ltd | Construction | 2014 |
| Bryon Ltd | Financial services | 2021 |
| Bryonia Consulting Limited | Professional & scientific | 2016 |
| BS4A Limited | Health & social care | 2018 |
| Bsdt Enterprises Ltd | Construction | 2025 |
| BSE Company D Limited | Information & communication | 2025 |
| BSG Ecom Ltd | Wholesale & retail | 2022 |
| Bside Club Ltd | Education | 2021 |
| Bside Enterprises Ltd | Education | 2022 |
| Bside Press Ltd | Information & communication | 2022 |
| Bside Professional Services Ltd | Education | 2022 |
| BSL Gaming Ltd | Information & communication | 2025 |
| Bsupa | Other services | 2008 |
| BTB Products Limited | Manufacturing | 2019 |
| Btbcs Ltd | Wholesale & retail | 2018 |
| BTC Midas Ltd | Wholesale & retail | 2016 |
| BTR Carpentry Ltd | Manufacturing | 2020 |
| Buba Marine Ltd | Manufacturing | 2020 |
| Bubble Magic Cleaning Services Ltd | Administrative & support | 2024 |
| Bubble Tea Party Ltd | Hospitality | 2021 |
| Bucephalus Capital Ventures Limited | Professional & scientific | 2019 |
| Buchan Chase Limited | Real estate | 2017 |
| Bucifal Ltd | Transport & logistics | 2019 |
| Buck & Co Property Ltd | Real estate | 2024 |
| Buckingham Concepts Ltd | Professional & scientific | 2003 |
| Buckingham Healthcare Limited | Wholesale & retail | 2001 |
| Buckingham Healthcare Services Limited | Manufacturing | 2017 |
| Buckland Care (Holdings) Limited | Financial services | 2012 |
| Buckland Care Limited | Health & social care | 2002 |
| Buckland Care Services Limited | Health & social care | 2006 |
| Buckler Heights (Parkstone) Management Company Limited | Households | 2014 |
| Buckley Whitmoor-Pryer Tracey House Ltd | Financial services | 2025 |
| Buckpay Limited | Wholesale & retail | 2025 |
| Budden Properties Limited | Real estate | 2017 |
| Buddha Hair & Beauty Ltd | Other services | 2016 |
| Budos Media Limited | Information & communication | 2014 |
| Buecora Limited | Wholesale & retail | 2023 |
| Buffalinos Limited | Wholesale & retail | 2025 |
| Buffalo Freehold Ltd | Hospitality | 2018 |
| Bufflunch Ltd | Information & communication | 2019 |
| Build and Influence Ltd | Professional & scientific | 2025 |
| Build Bournemouth Ltd | Construction | 2017 |
| Build ME UP Brickwork Ltd | Construction | 2020 |
| Buildez UK Ltd | Construction | 2025 |
| Building Brains Limited | Construction | 2018 |
| Building Control Projects Ltd | Construction | 1999 |