| 100KICKS Ltd | Professional & scientific | 2022 |
| 13 Amethysts Group Holdings Limited | Financial services | 2025 |
| 17 High Street Thame Management Company Limited | Real estate | 2015 |
| 1855 Oxford Limited | Hospitality | 2013 |
| 1973 Limited | Information & communication | 2004 |
| 1ST Intervention Care Ltd | Administrative & support | 2021 |
| 2 Collingbourne Road Limited | Extraterritorial | 2016 |
| 21ST Century Thame Limited | Other services | 2006 |
| 24A Limited | Information & communication | 2010 |
| 2695 Health Ltd | Information & communication | 2024 |
| 2C/D Addison Drive (Littlemore) Management Company Limited | Professional & scientific | 2005 |
| 3D Training Services Limited | Education | 2011 |
| 4 Play Developments Limited | Construction | 2009 |
| 4 Play Events Limited | Administrative & support | 2017 |
| 4B Studio Ltd | Professional & scientific | 2021 |
| 6 Addiction | Professional & scientific | 2023 |
| 7406 Medical Services Ltd | Health & social care | 2024 |
| 78/80 Howard Road London Limited | Real estate | 2003 |
| A D Wragg Plumbing and Heating Limited | Construction | 2007 |
| A J Griffin Limited | Construction | 2007 |
| A Kemp & Co Ltd | Professional & scientific | 2024 |
| A. B. Davies Consultancy and Design Limited | Professional & scientific | 2019 |
| Aaron Bonham Plumbing & Heating Ltd | Construction | 2024 |
| AB Contact Limited | Professional & scientific | 2012 |
| AB Vehicle Consultancy Ltd | Other services | 2023 |
| Ablemark Limited | Real estate | 1960 |
| Abpharm Analytical Consultancy Limited | Professional & scientific | 2012 |
| Abstractoy Ltd | Information & communication | 2024 |
| Abundance Studio Ltd | Professional & scientific | 2026 |
| Acceler-Ait Ltd | Professional & scientific | 2024 |
| Acentis Investments Limited | Professional & scientific | 2025 |
| Acorn IP LLP | | 2023 |
| Adactus Solutions Limited | Financial services | 2016 |
| Adapt Rich Media Ltd. | Information & communication | 2012 |
| Adav Design Ltd | Professional & scientific | 2024 |
| ADB Advisory Limited | Professional & scientific | 2019 |
| Adda Property Limited | Real estate | 2019 |
| Advanced Labelling Systems Limited | Manufacturing | 1997 |
| Advantage CX Limited | Information & communication | 2023 |
| Advent.Re Ltd | Energy | 2017 |
| Aedda's Farm Distillery Limited | Manufacturing | 2022 |
| Aevira Ltd | Manufacturing | 2025 |
| Affinity Trust | Health & social care | 2009 |
| Affinity Trust Support Ltd | Health & social care | 2021 |
| African Alpha Investment Partners Limited | Financial services | 2011 |
| AGH Plumbing Services Limited | Construction | 2010 |
| Aideen Lucey Consulting Limited | Professional & scientific | 2013 |
| Aidi DZ Ltd | Wholesale & retail | 2023 |
| AJM PM Ltd | Construction | 2014 |
| AJR Construction & Carpentry LLP | | 2026 |
| Akena Consulting Ltd | Professional & scientific | 2024 |
| Aktiva Systems Limited | Manufacturing | 1988 |
| AL3D Limited | Professional & scientific | 2012 |
| Alav Technology Limited | Information & communication | 2020 |
| Albury Books Limited | Information & communication | 2013 |
| Alchemist Compliance Ltd | Information & communication | 2018 |
| ALE Van, Bar & Events Limited | Hospitality | 2018 |
| Alex Covella Ltd | Information & communication | 2019 |
| Alex Gilligan Limited | Other services | 2017 |
| Alex Theodoridis-Jones | Extraterritorial | 2022 |
| Alexander Lowen Limited | Professional & scientific | 2026 |
| Alexandros Theodoridis Limited | Extraterritorial | 2022 |
| Alfred Edward Jones Limited | Extraterritorial | 2022 |
| Aligned AI Limited | Information & communication | 2021 |
| ALL Contracted Maintenance Ltd | Energy | 2020 |
| ALL Energy Limited | Professional & scientific | 2024 |
| ALL Sabers Ltd | Wholesale & retail | 2024 |
| Allmarkone Limited | Wholesale & retail | 2015 |
| Aloale Limited | Real estate | 2026 |
| Alysoun Owen Consulting Ltd | Professional & scientific | 2011 |
| AMB Communications Limited | Administrative & support | 1998 |
| Ambiance Developments Ltd | Professional & scientific | 2014 |
| Ambue Ltd | Information & communication | 2020 |
| Amethyst Legal Consulting Limited | Professional & scientific | 2021 |
| AMF Group Limited | Professional & scientific | 2003 |
| Amitypath Ltd | Professional & scientific | 2021 |
| Amuma Projects Limited | Real estate | 2024 |
| Andem Property Ltd | Real estate | 2019 |
| Anders Heating Company Limited | Construction | 2001 |
| Anders Holding Company Limited | Financial services | 2024 |
| Andrew Goddard Associates Limited | Health & social care | 2002 |
| Andrew Riley Properties Limited | Real estate | 2025 |
| Andrews Eades Limited | Professional & scientific | 2008 |
| Andy Hobbs Consulting Limited | Administrative & support | 2021 |
| Andy Writes Copy Ltd | Other services | 2019 |
| Anglo Wokingham Management Ltd | Real estate | 2006 |
| Ani-Go Limited | Information & communication | 2026 |
| Animade Group Limited | Professional & scientific | 2021 |
| Animade Ltd | Extraterritorial | 2015 |
| Anna Goss Ltd | Professional & scientific | 2025 |
| Annix Ltd | Information & communication | 2007 |
| Annix Studios Ltd | Information & communication | 2009 |
| Ansible Studio Ltd | Information & communication | 2021 |
| ANY Given Moment Ltd | Professional & scientific | 2024 |
| AP Energy Law Limited | Professional & scientific | 2011 |
| APA Parafricta Limited | Manufacturing | 2004 |
| Aphiri Services Ltd | Health & social care | 2019 |
| APK Building Services Ltd | Construction | 2026 |
| Apple Twin LAB Ltd | Information & communication | 2026 |
| APR Medtech Limited | Health & social care | 2014 |