| Berkshire Spa Limited | Health & social care | 2020 |
| Berlbot Limited | Transport & logistics | 2025 |
| Berniemanuel Health Consult Ltd | Health & social care | 2022 |
| Berrydown Garage Limited | Wholesale & retail | 2015 |
| Berryford Accountants Limited | Professional & scientific | 2018 |
| Berticar Ltd | Health & social care | 2017 |
| Bertin Exensor Limited | Manufacturing | 1988 |
| Bespoke CNC Ltd | Manufacturing | 2025 |
| Best Matic International Limited | Professional & scientific | 1985 |
| Best Time Limited | Transport & logistics | 2019 |
| Best Time Logistics Ltd | Transport & logistics | 2023 |
| Best Time Training Ltd | Education | 2025 |
| Beta Cars Ltd | Transport & logistics | 2025 |
| Betkei Ltd | Real estate | 2026 |
| Better Business for Good CIC | Administrative & support | 2026 |
| Better Returns Ltd | Wholesale & retail | 2016 |
| Beumy Development Ltd | Construction | 2021 |
| Bevan Media Limited | Information & communication | 2024 |
| Beware Scam Company & Website Ltd | Wholesale & retail | 2011 |
| Bexmatt Limited | Real estate | 2016 |
| Beyond News Desk Ltd | Information & communication | 2024 |
| Beyondlifehealthcare Ltd | Health & social care | 2017 |
| BG Electrical + Mechanical Limited | Construction | 2009 |
| BG Plumbing and Heating Ltd | Construction | 2017 |
| BGC Team Ltd | Construction | 2017 |
| BGD Daniel Ltd | Transport & logistics | 2022 |
| BGR Consultancy Ltd | Professional & scientific | 2024 |
| Bhakta & Daughters Ltd | Real estate | 2024 |
| Bharat Health Care Ltd | Health & social care | 2022 |
| Bhardwaj Residential Ltd | Real estate | 2025 |
| Bhavi Beauty Ltd | Other services | 2011 |
| BHL Heritage Holdings Ltd | Real estate | 2026 |
| Bialo Electrical Ltd | Construction | 2019 |
| Bidwork Construction Software Ltd | Information & communication | 2019 |
| Big D Marketing Limited | Information & communication | 2013 |
| Big RIG Ltd | Transport & logistics | 2015 |
| Bilicious Limited | Wholesale & retail | 2023 |
| Billpoint Consulting Ltd | Professional & scientific | 2023 |
| Biomerieux UK Limited | Manufacturing | 1972 |
| Bioveritas Partners Ltd | Professional & scientific | 2026 |
| Bird’S Gardening & General Repairs Ltd | Construction | 2026 |
| BIS Installations Limited | Construction | 2006 |
| Bishop & Brookes Limited | Health & social care | 2008 |
| Bisiello Limited | Wholesale & retail | 2025 |
| Bisque Direct Limited | Wholesale & retail | 2015 |
| Biston Private Limited | Health & social care | 2015 |
| Bitbox Ltd | Information & communication | 1995 |
| Bitoma Software Ltd | Information & communication | 2011 |
| BJG Heating & Plumbing Limited | Construction | 2023 |
| BJS Services Copmany Ltd | Information & communication | 2017 |
| BK Drive Ltd | Administrative & support | 2026 |
| Bk's Gymnastics Wear Ltd. | Wholesale & retail | 2016 |
| Black & White Accounting Limited | Professional & scientific | 2016 |
| Black & White Accounting Services Ltd | Extraterritorial | 2018 |
| Black Cat Creative Limited | Professional & scientific | 2008 |
| Black Goat Tattoo Collective LLP | | 2018 |
| Black Mountain Employee Benefits Ltd | Administrative & support | 2024 |
| Black Mountain Human Resources (UK) Limited | Administrative & support | 2008 |
| Black Mountain Services (UK) Ltd | Administrative & support | 1999 |
| Black Rock Estates Limited | Real estate | 1960 |
| Black Sixtytwo Limited | Professional & scientific | 2014 |
| Black Success Initiative CIC | Professional & scientific | 2025 |
| Black Swan Training Solutions Limited | Education | 2002 |
| Black Wallaroo Limited | Real estate | 2016 |
| Blackdam Basingstoke Ltd | Hospitality | 2023 |
| Blacklands Estate Ltd | Agriculture & fishing | 2017 |
| Bland Carpentry Ltd | Construction | 2003 |
| Blatchford Central Services Limited | Administrative & support | 2018 |
| Blatchford Limited | Manufacturing | 1919 |
| Blatchford Products Holdings Limited | Financial services | 2017 |
| Blatchford Products Limited | Manufacturing | 2002 |
| BLD Transit Limited | Manufacturing | 2026 |
| Blend & Bloom Limited | Wholesale & retail | 2015 |
| Blessed CA Limited | Public administration | 2024 |
| Blest Care Ltd | Health & social care | 2016 |
| Blinding Light Limited | Other services | 2000 |
| Blocknet IT Limited | Information & communication | 2025 |
| Bloomfield Analysis Ltd | Professional & scientific | 2013 |
| Bloomhill Insurance Solutions Limited | Financial services | 2007 |
| Bloomwood Limited | Real estate | 2022 |
| Blossom Day Nursery Limited | Education | 2011 |
| Blue Altitude Ltd | Education | 2013 |
| Blue Crest PTY Ltd | Financial services | 2011 |
| Blue DOT Child Law Limited | Extraterritorial | 2019 |
| Blue Flame Plumbers Ltd | Construction | 2009 |
| Blue Flame Plumbers West Site Limited | Construction | 2019 |
| Blue Kite IT Ltd | Information & communication | 2009 |
| Blue OWL Homes Limited | Construction | 2021 |
| Blue OWL Living Ltd | Real estate | 2023 |
| Blue Peter Garage Limited | Wholesale & retail | 2008 |
| Blue Robin Rentals Limited | Real estate | 2024 |
| Blue Sky Kitchen Design Limited | Manufacturing | 2024 |
| Blue Star Business Solutions Limited | Financial services | 2004 |
| Bluebell Gardening Limited | Administrative & support | 2024 |
| Bluebell Resources Limited | Health & social care | 2000 |
| Bluebell Security Software Limited | Information & communication | 2023 |
| Blueberry Business Support Limited | Professional & scientific | 2012 |
| Bluebridge Codes Ltd | Information & communication | 2025 |
| Bluedust Ltd | Information & communication | 2014 |
| Bluefinch Building Services Ltd | Construction | 2024 |