| Austin Jacobs Limited | Professional & scientific | 2013 |
| Auto Medics (EST 2010) Ltd | Wholesale & retail | 2013 |
| Autoalert Limited | Information & communication | 2004 |
| Avant Identity Limited | Information & communication | 2021 |
| Avighna Vels Solutions Ltd | Information & communication | 2015 |
| Avino Timber Systems Limited | Construction | 2025 |
| Avocet Investments Limited | Financial services | 1987 |
| Avtar Pardesi Ltd | Other services | 2014 |
| AW Properties 1 Ltd | Real estate | 2021 |
| AW21 Ltd | Professional & scientific | 2021 |
| Awvoices Limited | Arts & recreation | 2013 |
| Axiom Building Contractors Limited | Construction | 2025 |
| Axiom Cons Ltd | Information & communication | 2013 |
| Axiom Prop Ltd | Real estate | 2024 |
| Axiom Sports Limited | Wholesale & retail | 2024 |
| Axion NOW Events Ltd | Arts & recreation | 2025 |
| Axion NOW Ltd | Wholesale & retail | 2013 |
| Ayris Automotive Limited | Wholesale & retail | 2011 |
| Ayur Assets Ltd | Real estate | 2021 |
| Azicrest Ltd | Professional & scientific | 2019 |
| Azteq Environmental Limited | Manufacturing | 2005 |
| Azteq Merchant Services Limited | Information & communication | 2023 |
| B Chilcott Consulting Limited | Information & communication | 2017 |
| B Inspired Training Ltd | Education | 2012 |
| B Kane Contracting Ltd | Professional & scientific | 2015 |
| B N Vikas Ltd | Professional & scientific | 2025 |
| B.Shaw Investments Limited | Real estate | 2017 |
| BA Grill Ltd | Hospitality | 2019 |
| Back to Life Cleaning Services Limited | Administrative & support | 2019 |
| Backworx | Health & social care | 2010 |
| Badminton Court Management Limited | Real estate | 1997 |
| Bailey Woolf Limited | Professional & scientific | 2015 |
| Baker Leasing Limited | Financial services | 2001 |
| Balhara Housing Ltd | Real estate | 2023 |
| Ballward Limited | Wholesale & retail | 1986 |
| Balmoori IT Ltd | Information & communication | 2025 |
| Banlaoch Executive HR Ltd | Administrative & support | 2026 |
| Barnett Waddingham Capital Trustees Limited | Financial services | 1992 |
| Barnett Waddingham Trustees (1980) Limited | Extraterritorial | 1980 |
| Barnett Waddingham Trustees (1984) Limited | Financial services | 1984 |
| Barnett Waddingham Trustees (1992) Limited | Financial services | 1992 |
| Barnett Waddingham Trustees (1996) Limited | Financial services | 1995 |
| Barnett Waddingham Trustees (1997) Limited | Financial services | 1997 |
| Barnett Waddingham Trustees Limited | Financial services | 1986 |
| Barnett Waddingham Trustees Scotland Limited | Financial services | 1979 |
| Baron Estates Limited | Real estate | 1993 |
| Barracuda Amersham Ltd | Hospitality | 2016 |
| Barramundi Ltd | Information & communication | 2013 |
| Bathrooms Complete Limited | Construction | 2013 |
| Bay Tree Corporation Ltd | Administrative & support | 2022 |
| BB Property Developments Ltd | Construction | 2024 |
| BDI Creative Ltd | Professional & scientific | 2017 |
| Beach Street Limited | Professional & scientific | 1997 |
| Beacon Change Advisory Limited | Professional & scientific | 2024 |
| Beacon Educational Trust Limited (the) | Education | 1972 |
| Beaconsfield Beauty Ltd | Other services | 2019 |
| Beans Family Company Limited | Hospitality | 2024 |
| Beauty and Hair Ltd | Other services | 2025 |
| Beauty by CR Limited | Other services | 2019 |
| Beckman Coulter United Kingdom Limited | Wholesale & retail | 1959 |
| Beckman Holdings Limited | Professional & scientific | 1988 |
| Becky Mccall Limited | Professional & scientific | 2006 |
| Beech Court Residents Freehold Limited | Households | 2016 |
| Beechwood Close Residents Management Company Limited | Real estate | 2006 |
| Beer Nuts Ltd | Hospitality | 2024 |
| Belgravia Lighting Limited | Manufacturing | 1995 |
| Bell Consulting UK Limited | Information & communication | 2002 |
| Bella Professional Ltd | Wholesale & retail | 2024 |
| Belstone Property Services Limited | Professional & scientific | 1992 |
| BEN Lawrence Ltd | Wholesale & retail | 2016 |
| Benepay Ltd | Information & communication | 2020 |
| Benveer Limited | Health & social care | 2023 |
| Beskora Ltd | Wholesale & retail | 2025 |
| Bespoke Plumbing Services Limited | Construction | 2017 |
| Besselink and Jones Holdings Limited | Professional & scientific | 1997 |
| Best Value Transport Network Ltd | Transport & logistics | 2021 |
| Better Place Ventures Limited | Professional & scientific | 2013 |
| Betwiz Sports Ltd | Arts & recreation | 2013 |
| Bexman Limited | Professional & scientific | 2014 |
| Beyondlimitless Ltd | Wholesale & retail | 2024 |
| BGM Group Construction Limited | Financial services | 2026 |
| BGM Group Facilities Management Limited | Administrative & support | 2025 |
| BGM Group Holdings Limited | Financial services | 2024 |
| BGM Group Logistics Ltd | Financial services | 2024 |
| BGM Group Sustainability Ltd | Financial services | 2024 |
| BGM Specialists Ltd | Professional & scientific | 2020 |
| Bhai Kanhaiya Humanitarian AID Ltd | Other services | 2021 |
| Bharath Niti Vikas | Professional & scientific | 2025 |
| Bhsl Consulting Ltd | Information & communication | 2024 |
| Big Green Energy Ltd | Energy | 2021 |
| Big Shades Productions Limited | Arts & recreation | 2017 |
| Bijal IT Services Limited | Information & communication | 2024 |
| Billings & Grayson Pubs Ltd | Hospitality | 2026 |
| Billion Watt Associates LP | | 2012 |
| Billion Watt Ltd | Manufacturing | 2012 |
| Billion Watt Photography Ltd | Arts & recreation | 2012 |
| Black Balance TV Limited | Information & communication | 2009 |
| Black FOX Ventures Limited | Information & communication | 2024 |
| Black Virgo Ltd | Information & communication | 2018 |
| Blackcurrant Finance Ltd | Information & communication | 2021 |