| Billy-Sarks Care Ltd | Health & social care | 2024 |
| Bilsafe Ltd | Construction | 2023 |
| Bilshop Ltd | Wholesale & retail | 2025 |
| Bilvasoft Ltd | Information & communication | 2020 |
| Bilviz Ltd | Real estate | 2026 |
| BIM Project Delivery Ltd | Professional & scientific | 2026 |
| Bina Continental Ltd | Wholesale & retail | 2025 |
| Binary Cloud Solutions Ltd | Information & communication | 2026 |
| Binary Enterprises Ltd | Information & communication | 2016 |
| Binary Investments Ltd | Financial services | 2018 |
| Binary Quantum Ltd | Information & communication | 2022 |
| Binary Software Ltd | Information & communication | 2006 |
| Binarythm Limited | Information & communication | 2011 |
| Bingham and Co Accountants Ltd | Professional & scientific | 2018 |
| Binghams Consultancy Limited | Information & communication | 2020 |
| Binky Belle Ltd | Wholesale & retail | 2022 |
| BIO Aesthetica Ltd | Wholesale & retail | 2025 |
| Bio-Bean Limited | Manufacturing | 2013 |
| Biobak Limited | Real estate | 2024 |
| Biogenie Remediation UK Limited | Water & waste | 1992 |
| Biogenie Site Remediation Limited | Water & waste | 2000 |
| Bioguru Ltd | Manufacturing | 2020 |
| Biointeractions Limited | Professional & scientific | 1991 |
| Biomedart Reading Ltd | Information & communication | 2019 |
| Bioprocess Consulting Ltd | Professional & scientific | 2024 |
| Biosteo Limited | Education | 2012 |
| Bira Butterfly Investments Limited | Real estate | 2019 |
| Birch Tree Freehold Ltd | Households | 2015 |
| Birch Tree Holdings (Hart) Limited | Construction | 2022 |
| Birch Tree Residents Association Limited | Households | 1983 |
| Birchley Management Company Limited | Households | 2016 |
| Birdoak Ltd | Information & communication | 2020 |
| Birds Marsh View Chippenham Apartment Resident Management Company Limited | Households | 2020 |
| Birdsong Productions Limited | Arts & recreation | 2012 |
| Birmingham Cable Limited | Extraterritorial | 1988 |
| Biryanish Ltd | Hospitality | 2024 |
| Bishops Court (Ascot) Residents Association Limited | Households | 2001 |
| Bishops Court Management (Highbridge) Limited | Real estate | 2007 |
| Bishops Grove Consulting Limited | Construction | 2012 |
| Bishops Lodge Limited | Health & social care | 1975 |
| Bishops Roofing Services Limited | Construction | 2021 |
| Bishopswood Developments Ltd | Construction | 2024 |
| Bishopswood Pavilion Limited | Construction | 2007 |
| Bismith Ltd | Information & communication | 2015 |
| Bison&Beam Ltd | Wholesale & retail | 2025 |
| Bissett Consultancy Services Limited | Professional & scientific | 2024 |
| Bistroid Ltd | Information & communication | 2023 |
| Bitbeams Limited | Information & communication | 2009 |
| Bitbuzz UK Limited | Extraterritorial | 2012 |
| Bite Media Ltd | Information & communication | 2026 |
| Bitready Ltd | Information & communication | 2011 |
| Bizcast Technology Ltd | Information & communication | 2017 |
| Bizpoke Ltd | Professional & scientific | 2022 |
| BJ Focus Ltd | Information & communication | 2010 |
| BJA Creative Design Limited | Professional & scientific | 2004 |
| BJE Consultancy Limited | Real estate | 2022 |
| Bjhsec Ltd | Professional & scientific | 2016 |
| BJK Delivery Ltd | Transport & logistics | 2013 |
| BK Commerce Ltd | Wholesale & retail | 2024 |
| BK Visuals Ltd | Information & communication | 2025 |
| BKB Properties Limited | Real estate | 2024 |
| BKC Technologies Ltd | Information & communication | 2020 |
| Bker Developments Ltd | Construction | 2022 |
| BKH Investments Limited | Real estate | 2022 |
| Bkingdom Ltd | Real estate | 2018 |
| Bkry Ltd | Education | 2023 |
| BL Analysis Ltd | Information & communication | 2018 |
| BLA 2059 Limited | Extraterritorial | 2016 |
| BLA 2060 Limited | Extraterritorial | 2016 |
| Black & Blue Velvet Ltd | Administrative & support | 2026 |
| Black 5 44901 Company Limited | Professional & scientific | 2012 |
| Black and White Property Services Ltd | Real estate | 2015 |
| Black Berry Studios Ltd | Professional & scientific | 2007 |
| Black Box Network Services (UK) Limited | Information & communication | 1987 |
| Black Cat Displays Limited | Manufacturing | 2007 |
| Black Diamond UK Development Ltd | Construction | 2016 |
| Black Drum Limited | Real estate | 2025 |
| Black Ginger Limited | Wholesale & retail | 2007 |
| Black Gold Limited | Extraterritorial | 2005 |
| Black Ice Development Limited | Information & communication | 2017 |
| Black INK Music Limited | Information & communication | 1992 |
| Black Island Studios Limited | Arts & recreation | 1991 |
| Black Jack CRM Limited | Information & communication | 2021 |
| Black Laboratory Limited | Information & communication | 2008 |
| Black Marsh Apparel Ltd | Wholesale & retail | 2021 |
| Black Mesa Ltd | Information & communication | 2019 |
| Black Panther Security Services Ltd | Administrative & support | 2026 |
| Black PUG Consulting Limited | Professional & scientific | 2023 |
| Black Red Cosmetics Ltd | Wholesale & retail | 2019 |
| Black Velvet Styling Ltd | Wholesale & retail | 2025 |
| Blackcrown Property Management Ltd | Real estate | 2026 |
| Blackdown Solar Power Limited | Energy | 2010 |
| Blacksmith Publishing Limited | Information & communication | 2012 |
| Blackstone HH Limited | Real estate | 2024 |
| Blackwell Grange Solar Farm Limited | Energy | 2013 |
| Blackwell Investment Group Ltd | Real estate | 2025 |
| Blade Holdings Limited | Financial services | 2018 |
| Bladez Barbers Ltd | Other services | 2018 |
| Bladez Barbershop Ltd | Other services | 2023 |
| Blagattas Limited | Wholesale & retail | 2006 |