| Bisg Ltd | Financial services | 2026 |
| Bisman Convenience Store Ltd | Wholesale & retail | 2025 |
| Bistro Builders Ltd | Construction | 2016 |
| Bizimpro Ltd | Information & communication | 2024 |
| BK Collective Ltd | Wholesale & retail | 2026 |
| BK Wholesale Limited | Wholesale & retail | 2020 |
| BKS Services Ltd | Information & communication | 2016 |
| BL Removals Ltd | Other services | 2003 |
| Black and Brown Limited | Information & communication | 2016 |
| Black Edition Ltd | Construction | 2020 |
| Black Hawk Technology Co. Ltd | Information & communication | 2020 |
| Black ND Neurodiverse CIC | Health & social care | 2024 |
| Black Slate Estates Limited | Real estate | 2021 |
| Black Space Light Ltd | Hospitality | 2017 |
| Blackwood Learning Ltd | Professional & scientific | 2015 |
| Blair Builders Ltd | Construction | 2026 |
| Blake Anderson Ltd | Administrative & support | 2008 |
| Blam Pictures Limited | Information & communication | 2016 |
| Blanedell Limited | Arts & recreation | 1972 |
| Blanksons Limited | Other services | 2018 |
| Blast Coffee Ltd | Hospitality | 2023 |
| Blazeguard Fire Protection Ltd | Construction | 2023 |
| Blazer Court Limited | Households | 1990 |
| Blenheim Management Consultants Ltd | Professional & scientific | 2021 |
| Blinds and Poles Direct Ltd | Manufacturing | 2010 |
| Blossom Bargins Ltd | Wholesale & retail | 2021 |
| Blossoming Families Day Nursery Ltd | Health & social care | 2026 |
| Blowers Vape Shop (Woosley) Limited | Wholesale & retail | 2023 |
| Blowfish Investments Ltd | Real estate | 2016 |
| Blowfish Ltd | Wholesale & retail | 2011 |
| BLU LUX Limited | Arts & recreation | 2012 |
| Blue Adair Ltd | Financial services | 2021 |
| Blue Bella Blooms Limited | Wholesale & retail | 2009 |
| Blue Lake Associates Ltd | Administrative & support | 2023 |
| Blue Marine Consultants Ltd | Transport & logistics | 2017 |
| Blue Rose Property Development Ltd | Professional & scientific | 2023 |
| Blue Square Properties Ltd | Real estate | 2019 |
| Blue Starfish Ltd | Real estate | 2021 |
| Bluespec Decorating Limited | Construction | 2013 |
| Bluestar Holding Limited | Wholesale & retail | 2015 |
| Blurabbit Technologies Ltd | Information & communication | 2022 |
| BMJ Consultancy Ltd | Information & communication | 2012 |
| BMT Test Consultancy Ltd | Information & communication | 2018 |
| BNH in Limited | Real estate | 2015 |
| Boba TRÀ Ltd | Hospitality | 2024 |
| Boci Projects Ltd | Construction | 2024 |
| Bodhi Tree Property Management Limited | Real estate | 2018 |
| Body Management Clinic Limited | Health & social care | 2002 |
| Body Reactive Limited | Health & social care | 2018 |
| Bohemshops Limited | Wholesale & retail | 2025 |
| Boiler GAS Tech Limited | Construction | 2023 |
| Boiler Genius Ltd | Construction | 2020 |
| Bolero Consulting Ltd | Information & communication | 2019 |
| Boltic Limited | Transport & logistics | 2021 |
| Boltzemo Financial Services Limited | Financial services | 2020 |
| Bombay Blue Ltd | Health & social care | 2024 |
| Bombay Tadka Limited | Hospitality | 2022 |
| Bonzos Dog Services Limited | Other services | 2021 |
| Boss Global Consulting Ltd | Professional & scientific | 2019 |
| Boubker Delights Limited | Hospitality | 2019 |
| Boujee Bronze (Woolston) Limited | Other services | 2024 |
| Boujee Bronze Limited | Other services | 2024 |
| Boulton Locks Ltd | Other services | 2023 |
| Bounce Spa Group Ltd | Professional & scientific | 2019 |
| Boundless Media Ltd | Information & communication | 2022 |
| BOW Waves Ltd | Public administration | 2019 |
| Boyuexu Industrial Co., Ltd | Administrative & support | 2021 |
| Bozcutstyle Ltd | Other services | 2025 |
| BPC Alliance Ltd | Real estate | 2017 |
| Brackenbridge Properties Ltd | Real estate | 2022 |
| Bracknell New Sushi Limited | Hospitality | 2019 |
| Bradley & Co Estates Ltd | Real estate | 2012 |
| Brai Consulting Limited | Information & communication | 2026 |
| Brainbow Cloud Ltd | Education | 2024 |
| Brand New Music Limited | Information & communication | 1977 |
| Brand YOU Consultancy Ltd | Administrative & support | 2019 |
| Brandeco Capital LLP | | 2013 |
| Braye Aviation Limited | Professional & scientific | 2014 |
| Braye Demolition and Plant Services Ltd | Construction | 2007 |
| Braye Property Services Ltd | Other services | 2024 |
| Breach Sales Group Ltd | Administrative & support | 2025 |
| Breadzel Limited | Hospitality | 2025 |
| Breezebeacon UK Limited | Health & social care | 2016 |
| Brentford Dock Enterprises Limited | Households | 2000 |
| Brentford Dock Limited | Real estate | 1978 |
| Brevity Labs Limited | Information & communication | 2020 |
| Brian O Halloran Ltd | Construction | 2023 |
| Brice Lettings Limited | Real estate | 2020 |
| Brickcraft Builders Ltd | Construction | 2026 |
| Bridges (CTN) Limited | Wholesale & retail | 1997 |
| Bridges Retail Limited | Wholesale & retail | 2002 |
| Bridgman House LLP | | 2006 |
| Bridgman Investments Partnership Limited | Administrative & support | 2003 |
| Bridgwater Consulting Limited | Financial services | 2023 |
| Bright Change Ltd | Professional & scientific | 2014 |
| Bright Havens Care Limited | Health & social care | 2025 |
| Bright Music Limited | Arts & recreation | 1977 |
| Bright Records Limited | Professional & scientific | 1978 |
| Bright Red Mars Limited | Professional & scientific | 2014 |
| Bright Spark Engineering Ltd | Construction | 2020 |