| Birdies and Bombs Ltd | Wholesale & retail | 2025 |
| Bitsy Bites Limited | Hospitality | 2023 |
| BIZ Enterprise Ltd | Wholesale & retail | 2020 |
| Bizri Ltd | Wholesale & retail | 2024 |
| BJ Estates Ltd | Real estate | 2022 |
| Black Arrow Finance Limited | Administrative & support | 1963 |
| Black Arrow Group Limited | Financial services | 1959 |
| Black Astrum Limited | Manufacturing | 2011 |
| Black Wild Adventure Ltd | Wholesale & retail | 2021 |
| Blagrove Road Residents Co. Limited | Real estate | 2005 |
| Bless YOU Tribe Ltd | Information & communication | 2022 |
| Blissett Bookbinding Holdings Limited | Manufacturing | 1985 |
| Block Fashion Group Ltd | Wholesale & retail | 2025 |
| Bloom&Square London Ltd | Education | 2024 |
| Bloompark Software Services Limited | Information & communication | 2014 |
| Blossom 88 Ltd | Health & social care | 2025 |
| Blossom Childcare Ltd | Education | 2020 |
| Blue Ace Fashion House Limited | Wholesale & retail | 2014 |
| Blue Blockchain Ltd | Education | 2019 |
| Blue Cube Travel Limited | Administrative & support | 2003 |
| Blue Flame Works Ltd | Construction | 2024 |
| Blue Luan Ltd | Education | 2025 |
| Blue Octahedron Limited | Professional & scientific | 2018 |
| Blue Skies LAB Ltd | Professional & scientific | 2024 |
| Blue Star IT Consulting Limited | Information & communication | 2015 |
| Bluebridge Holding Group Ltd | Financial services | 2023 |
| Blueocean Technologies Private Ltd | Information & communication | 2024 |
| Bluepeak Commerce Ltd | Wholesale & retail | 2026 |
| Blueprint Coatings Ltd | Construction | 2025 |
| Blueprint Vista Limited | Professional & scientific | 2011 |
| Blueway Property Ltd | Construction | 2020 |
| Blufall Limited | Professional & scientific | 2017 |
| Blythewood Ltd | Information & communication | 2023 |
| Bmair PVS UK Limited | Manufacturing | 2024 |
| BMT22 Ltd | Transport & logistics | 2020 |
| Bochi Ltd | Wholesale & retail | 2012 |
| Bodywise Training Ltd | Other services | 2014 |
| Bogd Ltd | Wholesale & retail | 2022 |
| BOLM4 Limited | Wholesale & retail | 2008 |
| Boltons Lane Freehold Limited | Real estate | 2016 |
| Bondi Baby Ltd | Wholesale & retail | 2025 |
| Booch Ltd | Hospitality | 2024 |
| Book Square Publishing Ltd | Information & communication | 2022 |
| Bookisho Limited | Information & communication | 2023 |
| Bookstop Services (UK) Limited | Wholesale & retail | 2008 |
| Bornagen Ltd | Wholesale & retail | 2026 |
| Boston Cafe Limited | Hospitality | 2018 |
| Boston Solutions Ltd | Construction | 2010 |
| Boswie Ltd | Administrative & support | 2023 |
| Botta Pathodynamics LLP | | 2025 |
| Bouche Bakehouse Limited | Manufacturing | 2015 |
| Bourke Accountants LLP | | 2003 |
| Bourke Properties LLP | | 2013 |
| Bournes Riviera Ltd | Wholesale & retail | 2026 |
| Bowland Associates Limited | Information & communication | 2020 |
| Bown Design & Build Limited | Construction | 2008 |
| Box Back UK Limited | Transport & logistics | 2021 |
| Boxtik Content Ltd | Information & communication | 2022 |
| Boys GET SAD TOO Ltd | Wholesale & retail | 2019 |
| Bpur Ltd | Health & social care | 2019 |
| BQF Limited | Wholesale & retail | 2026 |
| Braca Ltd | Professional & scientific | 2026 |
| Bradford Daniels Limited | Administrative & support | 2017 |
| Braemar Gunn Ltd | Professional & scientific | 2017 |
| Brand Remedy Ltd | Professional & scientific | 1994 |
| Brand Spark Media Ltd | Professional & scientific | 2025 |
| Brandvista Consulting Ltd | Professional & scientific | 2024 |
| Break Through I.T. Ltd | Information & communication | 1999 |
| Breakin Bread Publishing Limited | Information & communication | 2002 |
| Breakin Bread Records Limited | Information & communication | 2002 |
| Breelde Pro Limited | Information & communication | 2022 |
| Brent Optical Limited | Wholesale & retail | 2018 |
| Brent Pharma Limited | Wholesale & retail | 2018 |
| Brent Property Ltd | Real estate | 2016 |
| Brentford Bicycle Works Limited | Other services | 2026 |
| Brentford Cafe House Ltd | Hospitality | 2024 |
| Brentford Cafe Plus Ltd | Hospitality | 2025 |
| Brentford Community Boat House | Arts & recreation | 2023 |
| Brentford FC Community Sports Trust | Education | 2005 |
| Brentford FC Limited | Arts & recreation | 1998 |
| Brentford Food & Wine Ltd | Wholesale & retail | 2019 |
| Brentford Homes Limited | Real estate | 2024 |
| Brentford Management Company Limited | Households | 1994 |
| Brentford News & OFF License Ltd | Wholesale & retail | 2016 |
| Brentford Nylons Limited | | 1959 |
| Brentford Riviera Limited | Real estate | 2023 |
| Brentford Rugby House Limited | Hospitality | 2020 |
| Brentford School for Girls | Education | 2012 |
| Brentford SIX Bells Ltd | Hospitality | 2023 |
| Brentford Studios Limited | Information & communication | 2024 |
| Brentford Voice CIC | Public administration | 2019 |
| Brentford Walks Community Interest Company | Health & social care | 2025 |
| Brentside Communications Limited | Information & communication | 1986 |
| Bridge Digital Media Ltd | Professional & scientific | 2020 |
| Bridgeview Care Ltd | Health & social care | 2025 |
| Bridgeview Transport Ltd | Transport & logistics | 2025 |
| Bridgeway Transport Ltd | Transport & logistics | 2026 |
| Bright & White DRY Cleaners Limited | Other services | 2013 |
| Bright Star Healthcare Limited | Health & social care | 2017 |
| Brightstar Care Solutions Ltd | Health & social care | 2024 |