| Bostock Property Ltd | Real estate | 2023 |
| Bothongo Rehman Properties Ltd | Administrative & support | 2019 |
| Bothwick Finance Ltd | Financial services | 2020 |
| Boundless Creative Ltd | Information & communication | 2024 |
| Bourdeaux Limited | Households | 2011 |
| Boutique Distillation Ltd | Other services | 2011 |
| Bowlers Consultancy Ltd | Extraterritorial | 2023 |
| Bowmon Legal Costs Limited | Professional & scientific | 2013 |
| BOWSIDE7 Limited | Professional & scientific | 2020 |
| Bowyer IT Solutions Limited | Information & communication | 2005 |
| Box & Charnock Holdings Ltd | Professional & scientific | 2008 |
| Box & Charnock Limited | Construction | 1977 |
| Box & Charnock Maintenance Ltd | Extraterritorial | 2010 |
| Box AL Arabi Ltd | Hospitality | 2025 |
| Box and Defeo Builders Limited | Construction | 2025 |
| Box and Defeo Developments Limited | Real estate | 2014 |
| Box and Defeo Ltd | Construction | 2003 |
| Box Clever Display Ltd | Administrative & support | 2008 |
| Box END Firewood Ltd | Agriculture & fishing | 2016 |
| Box END Park Holdings Limited | Arts & recreation | 2019 |
| Box END Park Limited | Arts & recreation | 2019 |
| Box END Park Retreats Limited | Construction | 2019 |
| Box END Physiotherapy Limited | Health & social care | 2026 |
| Boyden Scaffold Solutions Ltd | Construction | 2024 |
| Boyds of Bedford Ltd | Wholesale & retail | 2015 |
| Boyee Trading Ltd | Wholesale & retail | 2019 |
| Boynett & Co (1902) Ltd | Manufacturing | 2024 |
| Boyracers UK Limited | Wholesale & retail | 2004 |
| Boytech Limited | Professional & scientific | 2022 |
| Bozan Trans Ltd | Wholesale & retail | 2017 |
| Bozyer Ltd | Hospitality | 2025 |
| Bozzmoss Ltd | Other services | 2025 |
| Bpaul Construction Ltd | Construction | 2023 |
| Bpha Finance PLC | Financial services | 2014 |
| BPT Web Wellness London Ltd | Administrative & support | 2021 |
| Brackhampton Limited | Education | 2023 |
| Brackley Autos Ltd | Wholesale & retail | 2023 |
| Brad Bell Fitness Ltd | Arts & recreation | 2025 |
| Brade Homes Ltd | Real estate | 2022 |
| Bradley Miles Drylining Limited | Manufacturing | 2021 |
| Bradley World Investments Limited | Real estate | 2020 |
| Bradshaws (Haynes) Limited | Transport & logistics | 2012 |
| Brady Medical Consultancy Limited | Health & social care | 2005 |
| Braeburn Developments Limited | Construction | 2005 |
| Braemar RRC Limited | Real estate | 2020 |
| Braham Bhakta Ltd | Other services | 2007 |
| Brainiac Group Ltd | Administrative & support | 2022 |
| Braintree Insurance Services Ltd | Financial services | 2023 |
| Bramble & Bark Ltd | Wholesale & retail | 2025 |
| Bramble & Navy Ltd | Wholesale & retail | 2023 |
| Bramham Mead (Management Company) Limited | Households | 1988 |
| Branchtree Investments Ltd | Real estate | 2021 |
| Brand Raven Ltd | Professional & scientific | 2014 |
| BRAND63 Ltd | Manufacturing | 2024 |
| BRAND63AFRICA C.I.C. | Other services | 2025 |
| Brandberg Ltd | Information & communication | 2017 |
| Brandleap Ltd | Information & communication | 2025 |
| Brands View Developments Limited | Construction | 2019 |
| Brandstrat Ltd | Arts & recreation | 2016 |
| Branglen Properties Limited | Households | 1973 |
| Brava Groundworks Limited | Construction | 2026 |
| Brave Breathwork Ltd | Other services | 2024 |
| Bravora Group Ltd | Professional & scientific | 2025 |
| Braymad Limited | Financial services | 2021 |
| Brazil to Your House Ltd | Wholesale & retail | 2016 |
| Brcc Trading Services Limited | Administrative & support | 2002 |
| BRD Financial Ltd | Financial services | 2019 |
| Breakdown and Service Limited | Professional & scientific | 2001 |
| Breaking the Binary Ltd | Education | 2021 |
| Breesantos Ltd | Wholesale & retail | 2021 |
| Brennan Plant & Land Limited | Wholesale & retail | 2023 |
| Brennan West Limited | Construction | 2025 |
| Brentford Decorators Limited | Construction | 2007 |
| Brew Empire Limited | Wholesale & retail | 2025 |
| Brewery Lane (Baldock) Management Company Limited | Households | 2005 |
| Brice Equestrian Ltd | Agriculture & fishing | 2022 |
| Brick Hill Coffee Post Ltd | Wholesale & retail | 2019 |
| Brick&Bondz Ltd | Real estate | 2024 |
| Brickbooks and Payroll Ltd | Professional & scientific | 2022 |
| Brickbuild Construction Limited | Construction | 2009 |
| Brickhill HCW Ltd | Administrative & support | 2023 |
| Brickhill Valeting Ltd | Other services | 2023 |
| Bricklet Ltd | Real estate | 2025 |
| Bricksmith Property Ltd | Real estate | 2025 |
| Bridge Comply Ltd | Information & communication | 2023 |
| Bridge Project Management Ltd | Professional & scientific | 2003 |
| Bridge Recruitment UK Limited | Administrative & support | 2004 |
| Brigadier Wear Limited | Wholesale & retail | 2022 |
| Bright and Rise Children Homes Limited | Health & social care | 2025 |
| Bright Care Staffing Ltd | Other services | 2024 |
| Bright Emotions CIC | Other services | 2021 |
| Bright Future Investments Limited | Financial services | 2013 |
| Bright Horizon Children's Home Limited | Health & social care | 2025 |
| Bright Horizon Creative Limited | Information & communication | 2025 |
| Bright I Ltd | Wholesale & retail | 2021 |
| Bright Path Community Services Community Interest Company | Administrative & support | 2024 |
| Bright Sun Healthcare Ltd | Health & social care | 2021 |
| Brightedge Services Ltd | Administrative & support | 2025 |
| Brightman Joinery Limited | Manufacturing | 2024 |
| Brighton Beautiful Design Limited | Wholesale & retail | 2017 |