| Atomic Topco 1 Limited | Financial services | 2025 |
| Atomic Wealth Management Limited | Financial services | 2014 |
| ATP Oxford International Education Ltd | Education | 2013 |
| Atropakan Limited | Manufacturing | 2019 |
| Atticbest Limited | Construction | 1994 |
| Attwood AI Consulting Limited | Information & communication | 2017 |
| AU Letting Limited | Real estate | 2025 |
| Audace Oxbridge Learning Limited | Education | 2025 |
| Audacieu Ltd | Information & communication | 2026 |
| Audharrid Ltd | Real estate | 2021 |
| Audio Computer Ltd | Manufacturing | 2023 |
| Audiomotion Studios Limited | Other services | 2002 |
| Audioplatter Limited | Information & communication | 2020 |
| Audit Holdings 1 Limited | Real estate | 2016 |
| Audit Holdings 2 Limited | Real estate | 2017 |
| Audit Holdings 25 Limited | Real estate | 2017 |
| Audit Holdings 4 Limited | Real estate | 2018 |
| Auditcare Kirlena House Limited | Health & social care | 2014 |
| Auditcare MON Choisy Limited | Health & social care | 2014 |
| Auditorium Parvum Ltd | Education | 2024 |
| Audrey Care and Housing Ltd | Hospitality | 2024 |
| Audreys Court (OCK Street) Management Limited | Households | 2016 |
| Augustus Kumars Limited | Real estate | 2015 |
| Aura (Oxford) Limited | Construction | 2017 |
| Auraamp & Co Ltd | Wholesale & retail | 2026 |
| Aurelia Property Holdings Limited | Real estate | 2024 |
| Auremont Services Ltd | Wholesale & retail | 2026 |
| Aurevo Cleaning Services Ltd | Administrative & support | 2025 |
| Auro Limited | Information & communication | 2021 |
| Aurora Energy Research Limited | Professional & scientific | 2013 |
| Aurora Productions Limited | Administrative & support | 2026 |
| Aurore Jacobs Ltd | Other services | 2019 |
| Austen Guardian Angel Limited | Other services | 2017 |
| Auteur Film Productions UK Ltd | Information & communication | 2020 |
| Autism Champions CIC | Education | 2020 |
| Autism Specialist Transport Limited | Transport & logistics | 2021 |
| Auto Vettura Garage Services Ltd | Wholesale & retail | 2023 |
| Autoenhanceuk Ltd | Professional & scientific | 1981 |
| Autoluggage Limited | Professional & scientific | 1992 |
| Automorphic Limited | Professional & scientific | 2025 |
| Automotive Investments Holdings Group UK Limited | Manufacturing | 2022 |
| Auttal Ltd | Information & communication | 2023 |
| Auzano Capital Management Limited | Financial services | 2021 |
| Avahana Limited | Real estate | 2024 |
| Avalon Construction (Oxford) Limited | Construction | 2005 |
| Averthur NGO Consulting Limited | Professional & scientific | 2016 |
| Avery Studio Ltd | Manufacturing | 2022 |
| Aveshe Consultancy International Ltd | Professional & scientific | 2019 |
| Avis Hayes Limited | Households | 1990 |
| Avon Searches Limited | Professional & scientific | 2006 |
| Avonshield Products Limited | | 1981 |
| Avouch AI Ltd | Information & communication | 2026 |
| Awaman Limited | Transport & logistics | 2015 |
| Awan Heating and Electrical Limited | Professional & scientific | 2015 |
| Awan Traderz Limited | Wholesale & retail | 2012 |
| Aware Presence Limited | Education | 2012 |
| Awci Limited | Construction | 2012 |
| Awesam Creative Limited | Education | 2015 |
| Awesome A-Team Sales Limited | Professional & scientific | 2022 |
| Awhy Investment Ltd | Extraterritorial | 2021 |
| AWT INT Ltd | Wholesale & retail | 2025 |
| Axiom Financial Services Ltd | Financial services | 2006 |
| Axion Biosystems Holding UK Limited | Financial services | 2021 |
| Axion Solution Associates Ltd | Administrative & support | 2019 |
| Axiot Limited | Information & communication | 2005 |
| Axis Company Growth Limited | Information & communication | 2025 |
| Axon Software Consultants Ltd | Information & communication | 2003 |
| Axor Group Limited | Financial services | 2016 |
| Axoralab Ltd | Information & communication | 2025 |
| Axportica Ltd | Wholesale & retail | 2025 |
| AXR Golden Eagle Ltd | Households | 2023 |
| Axtell Electrical Ltd | Construction | 2019 |
| Axtonvext Logic Ltd | Information & communication | 2026 |
| Axyz Limited | Professional & scientific | 2024 |
| AY Oxford Ltd | Hospitality | 2025 |
| AYINTAP27 Ltd | Hospitality | 2021 |
| Aylesbury XYZ Ltd | Hospitality | 2018 |
| Aylestone Strategic Management Limited | Professional & scientific | 1993 |
| Aylward-Mills Consulting Ltd | Professional & scientific | 2018 |
| Aymonix Ltd | Wholesale & retail | 2026 |
| Ayoade Limited | Health & social care | 2022 |
| Ayra’S Aesthetics Ltd | Other services | 2024 |
| Aywagardens Limited | Real estate | 2022 |
| Aywarestaurants Limited | Hospitality | 2022 |
| AZA Plumbing and Heating Ltd | Construction | 2025 |
| Azam & Sons Ltd | Real estate | 2017 |
| Azeeahmed Oxford Ltd | Administrative & support | 2016 |
| Azimuth Financial (Oxford) Limited | Professional & scientific | 2021 |
| Aztec Nexus Ltd | Construction | 2025 |
| B & H Creative Studio Ltd | Manufacturing | 2026 |
| B & K Rosette Limited | Health & social care | 2014 |
| B & R Cleaning Services Limited | Administrative & support | 2008 |
| B & S Fashions Ltd | Wholesale & retail | 2025 |
| B C Legal Services Ltd | Professional & scientific | 2026 |
| B Hayden Property Services Limited | Construction | 2017 |
| B K Electronics Limited | Administrative & support | 2012 |
| B M Developments (Oxford) Limited | Construction | 2021 |
| B P Lawes (Summertown) Ltd | Professional & scientific | 2025 |
| B S Glass and Glazing Ltd | Manufacturing | 2008 |
| B UKA Builders Oxford Ltd | Construction | 2025 |