| Blueprint Advisory Group Ltd | Professional & scientific | 2026 |
| Blueprint Architectural Hardware Limited | Wholesale & retail | 2021 |
| Blueprint Specification Limited | Wholesale & retail | 2021 |
| Bluestone Enterprise Ltd | Wholesale & retail | 2025 |
| Bluewave Events Ltd | Arts & recreation | 2026 |
| Bluewave Korean Martial Arts Limited | Education | 2022 |
| Bluezone Care Ltd | Health & social care | 2020 |
| Bluheight Limited | Households | 1986 |
| Blus ARE US Media Limited | Wholesale & retail | 2025 |
| Blush and Blaze Ltd | Wholesale & retail | 2024 |
| BM Scaffolding Consultant Ltd | Professional & scientific | 2025 |
| BMA Consulting Engineers Ltd | Professional & scientific | 2019 |
| BMS Group (Holdings) Ltd | Construction | 2007 |
| BMS Services Limited | Construction | 2005 |
| BNC Gurkha Grocery Limited | Wholesale & retail | 2008 |
| BNP Paribas Lease Group Limited | Financial services | 1989 |
| BNP Paribas Leasing Solutions Limited | Financial services | 1967 |
| BNP Paribas Rental Solutions Limited | Administrative & support | 2003 |
| BNU Limited | Construction | 2022 |
| Boaz Busbar and Switchgear Group Ltd | Construction | 2024 |
| BOB Berry Fencing Limited | Construction | 2013 |
| BOB Upton Ltd | Administrative & support | 2008 |
| Bodmas Clinical Services Limited | Professional & scientific | 2014 |
| Body Perfect Pilates Limited | Arts & recreation | 2019 |
| Bodycraft Vehicle Body Repair Specialists Ltd | Wholesale & retail | 2010 |
| Boerie Ltd | Manufacturing | 2021 |
| Bohohaus Ltd | Real estate | 2020 |
| Boilerjax Ltd | Construction | 2023 |
| Bolivia Holdings Ltd | Real estate | 2016 |
| Bolivia Lofts Ltd | Construction | 2024 |
| Boluwatife Ltd. | Wholesale & retail | 2017 |
| Bombshell Hair & Beauty Ltd | Other services | 2014 |
| Bonsbrothers Limited | Hospitality | 2023 |
| Book, Bird and Barrel Ltd | Administrative & support | 2025 |
| Boom Coms Limited | Information & communication | 2018 |
| Boom Holdings Limited | Financial services | 2018 |
| Boom Machinery Sales Ltd | Wholesale & retail | 2018 |
| Boom Phones Limited | Information & communication | 2013 |
| Boop Petcare Limited | Other services | 2019 |
| Boops Group Limited | Wholesale & retail | 2023 |
| Borman Projects Limited | Real estate | 2018 |
| Boshier Limited | Professional & scientific | 2015 |
| Bosss HI Ltd | Administrative & support | 2025 |
| Botanicals & Natural Products Limited | Wholesale & retail | 1998 |
| Bottomline Services Limited | Health & social care | 2023 |
| Boudica Design Limited | Other services | 2021 |
| Boudica Trading Ltd | Wholesale & retail | 2025 |
| Bounce in a Day Ltd | Administrative & support | 2024 |
| Bourne Again Aesthetics Ltd | Other services | 2024 |
| Bousiou Consulting Ltd | Professional & scientific | 2022 |
| BOW House Holdings Limited | Health & social care | 2018 |
| Bowe Plumbing Limited | Construction | 2024 |
| Bowman Property Management Ltd | Financial services | 2016 |
| Box Hairdressers Limited | Other services | 2002 |
| Boxxo Limited | Wholesale & retail | 2021 |
| Boyd-Phillips Construction Ltd | Construction | 2023 |
| Bpma Consulting Limited | Wholesale & retail | 2015 |
| Bpma Property LLP | | 2021 |
| Brace Engineering Limited | Administrative & support | 2024 |
| Brackenwood Windows Limited | Construction | 1987 |
| Bradley James Classics Ltd | Wholesale & retail | 2015 |
| Brads Bathrooms Ltd | Construction | 2022 |
| Brammo Trading Ltd | Wholesale & retail | 2024 |
| Brazilian Holdings Limited | Financial services | 1950 |
| Brazilian Properties Limited | Financial services | 2003 |
| Brazilian Street Food Limited | Manufacturing | 2023 |
| Breakpoint Research Holdings Limited | Financial services | 2025 |
| Breakpoint Research Limited | Information & communication | 2025 |
| Breeze Cars Limited | Transport & logistics | 2023 |
| Brendan Moran Ltd | Health & social care | 2010 |
| Brett Grellier Psychology Services Limited | Health & social care | 2016 |
| Brett Ruth Auto Ltd | Manufacturing | 2012 |
| Bretts Polar White Plastics Ltd | Construction | 1997 |
| Brevity Marketing Limited | Professional & scientific | 2010 |
| Brew Securities Ltd | Professional & scientific | 1978 |
| Brewery Place Residents Management Company Limited | Households | 2021 |
| Brian Streeter Guitar Services Ltd | Information & communication | 2024 |
| Brianne Consulting Ltd | Professional & scientific | 2012 |
| Brick Red Building Services Ltd | Construction | 2023 |
| Brickhaus Construction Ltd | Construction | 2026 |
| Bricks and Mortar Innovations Ltd | Information & communication | 2025 |
| Bridge Consulting Solutions Limited | Professional & scientific | 2023 |
| Bridge Design and Visualisation Ltd | Professional & scientific | 2025 |
| Bridge Facilities Management Ltd | Administrative & support | 2019 |
| Bridge House Entertainment Limited | Arts & recreation | 2009 |
| Bridge House Professional Management Services Limited | Professional & scientific | 2013 |
| Bridge Management Consulting Services Limited | Professional & scientific | 2007 |
| Bridgefast Management Limited | Real estate | 1995 |
| Bridging Gapz Ltd | Information & communication | 2021 |
| Brigadier Sweets Ltd | Wholesale & retail | 2025 |
| Brighton Sommerfugl Limited | Financial services | 2020 |
| Brightthing Advisors Limited | Professional & scientific | 2014 |
| Brightthing Brands Limited | Professional & scientific | 2020 |
| Brika Investments Ltd | Real estate | 2022 |
| Brill Folks Ltd | Wholesale & retail | 2022 |
| Brill Plumbing and Heating Limited | Construction | 2023 |
| Brimstone Design Limited | Professional & scientific | 2018 |
| Brit Brush Ltd | Construction | 2018 |
| Brit Parts Motors Ltd | Wholesale & retail | 2022 |
| Britannic Film and Television Limited | Information & communication | 1982 |