| Aprl Consulting Limited | Professional & scientific | 2024 |
| Aquilla Europe Ltd | Professional & scientific | 2009 |
| Arboreal Risk Advisors LLP | | 2022 |
| Archella Group Ltd | Professional & scientific | 2011 |
| Argosy Components Limited | Wholesale & retail | 1984 |
| ARP Music Limited | Information & communication | 2016 |
| Arrow Claims Management Services Limited | Administrative & support | 2001 |
| Arthur Vergani Design Ltd | Professional & scientific | 2026 |
| Ashbridge Holdings Limited | Professional & scientific | 2021 |
| Ashburton House Care Home Ltd | Health & social care | 2020 |
| Ashridge Homes Limited | Construction | 2023 |
| ASI Investments Ltd | Real estate | 2018 |
| Aspen Financial Advice Ltd | Financial services | 2014 |
| Aspen Saunas Limited | Construction | 2025 |
| Assist Knowledge Development Limited | Administrative & support | 1997 |
| Associatethis Limited | Information & communication | 2005 |
| Astron Energy Limited | Professional & scientific | 2025 |
| Atalay Cafe Ltd | Hospitality | 2026 |
| Atcd Construction Ltd | Construction | 2023 |
| Athelas Testing Limited | Information & communication | 1997 |
| Atomic BEE Limited | Administrative & support | 2015 |
| Attwood Baker Limited | Administrative & support | 2006 |
| Atum Intelligence Ltd | Professional & scientific | 2025 |
| Augmented Engineering Ltd | Professional & scientific | 2017 |
| Auricas Limited | Professional & scientific | 2001 |
| Aurora Helicopters Ltd | Manufacturing | 2022 |
| Auros Coffee Ltd | Wholesale & retail | 2024 |
| Aurox Limited | Manufacturing | 2004 |
| Auto Torque (Bucks) Limited | Manufacturing | 2010 |
| Autokeys Group Limited | Wholesale & retail | 2025 |
| Automation Integration Limited | Professional & scientific | 2017 |
| Autotek Engineering Ltd | Information & communication | 2015 |
| Autumn Engineering (Nottingham) Limited | Manufacturing | 2005 |
| Autumn Years Care Group Limited | Health & social care | 2017 |
| AVA Rose Design Ltd | Professional & scientific | 2023 |
| AVA Rose Marketing Ltd | Professional & scientific | 2020 |
| AVA Rose Property Ltd | Real estate | 2020 |
| Avenue One Graphics Ltd | Manufacturing | 1992 |
| Aviatorx Limited | Information & communication | 2023 |
| AW & DJ Evans Investments Limited | Financial services | 2021 |
| Awynbooks Limited | Administrative & support | 2003 |
| Axford Engineering Services Limited | Wholesale & retail | 2003 |
| Aylesbury Women's AID | Health & social care | 1996 |
| Azure Oxford Limited | Professional & scientific | 2024 |
| Azure Strategy Ltd | Information & communication | 2020 |
| Azureus Solutions Limited | Professional & scientific | 2009 |
| B B Golf Limited | Arts & recreation | 2024 |
| B Maslin Holdings Ltd | Financial services | 2025 |
| B Maslin Lending Ltd | Financial services | 2025 |
| B'S Street EAT Limited | Hospitality | 2021 |
| B4 National Limited | Professional & scientific | 2021 |
| Bailors Limited | Agriculture & fishing | 2025 |
| BAL Property Limited | Real estate | 2016 |
| Ballers Creed Ltd | Education | 2025 |
| Bambinos Nursery Group Limited | Financial services | 2026 |
| Bannard Insurance Brokers Ltd | Financial services | 2020 |
| Banning’S Fleet Services Ltd | Wholesale & retail | 2022 |
| Barbara (Aylesbury) Limited | Hospitality | 1946 |
| Barr Build Ltd | Construction | 2021 |
| Barr Group Ltd | Construction | 2007 |
| Barr Joinery Limited | Construction | 2012 |
| Barr Kitchens Limited | Construction | 2012 |
| Barre Sculpt Limited | Other services | 2013 |
| Barrns Ltd | Construction | 2022 |
| Barton Fleming Developments Limited | Real estate | 2021 |
| Barton Fleming Lettings Limited | Real estate | 2011 |
| Barton Fleming Limited | Real estate | 2011 |
| BASE16 Limited | Professional & scientific | 2015 |
| Basilikum Holdings Ltd | Administrative & support | 2017 |
| BAT Angels Ltd | Arts & recreation | 2016 |
| Beal Consulting Engineers Limited | Professional & scientific | 2010 |
| Belfurt Limited | Financial services | 2015 |
| Belingus Ltd | Education | 2018 |
| Bella Sharma Ltd | Transport & logistics | 2025 |
| Belmont Mews Residents Association Limited | Households | 1975 |
| Bematrix UK Ltd | Wholesale & retail | 2016 |
| BEN Gill Films Limited | Professional & scientific | 2013 |
| BEN Lambert Ltd | Administrative & support | 2010 |
| Benigni Ltd | Professional & scientific | 2019 |
| Berkshire Buckinghamshire and Oxfordshire Golf Limited | Arts & recreation | 2017 |
| Berryfields Healthcare Limited | Real estate | 2019 |
| Better Outcomes Consulting Ltd | Professional & scientific | 2025 |
| Bianchi Aviation Film Services Limited | Other services | 1984 |
| Big GAY OUT UK C.I.C. | Other services | 2023 |
| Big ME Ltd | Information & communication | 2024 |
| Bigrigs Services Ltd | Construction | 2022 |
| Bio-Sep Limited | Professional & scientific | 2023 |
| Biogul Ltd | Information & communication | 2023 |
| Biome Oxford Limited | Professional & scientific | 2015 |
| Biopharma Illuminata Ltd | Professional & scientific | 2023 |
| Birch Reynardson and Co Limited | Professional & scientific | 2011 |
| Birts Medical LLP | | 2019 |
| Bisiness Limited | Information & communication | 2018 |
| Bitcrest Limited | Information & communication | 2009 |
| BJB Landscapes Ltd | Administrative & support | 2022 |
| BJC London Ltd | Professional & scientific | 2010 |
| Black Finch Design Limited | Professional & scientific | 2016 |
| Black Hound Tattoo Limited | Other services | 2023 |
| Black Prince Fury Ltd | Information & communication | 2018 |
| Blackfrog Studios Ltd | Information & communication | 2009 |