| ADF Tree & Garden Maintenance Ltd | Agriculture & fishing | 2025 |
| Adgenix Ltd | Health & social care | 2024 |
| ADI Hand Carwash Limited | Health & social care | 2018 |
| ADI People Solutions Limited | Professional & scientific | 2019 |
| Adinstruments Limited | Information & communication | 1991 |
| Adipro UK & Europe Ltd | Wholesale & retail | 2024 |
| Adjoint Labs Limited | Professional & scientific | 2025 |
| Admans and Bryant Limited | Construction | 2008 |
| Admiral Home Developments Ltd | Construction | 2025 |
| Admiral Partners Ltd | Hospitality | 2018 |
| ADR Prime Paints Ltd | Construction | 2022 |
| Adrian and Helen Venture Limited | Hospitality | 2016 |
| Adrian Gould Mrtpi Ltd | Professional & scientific | 2011 |
| Adrian James Architects Limited | Professional & scientific | 2003 |
| Adult Brothers Deliver Ltd | Wholesale & retail | 2025 |
| ADV Technologies Limited | Professional & scientific | 2014 |
| Advance Display Solutions Limited | Manufacturing | 1998 |
| Advanced AI Diagnostics Ltd | Manufacturing | 2025 |
| Advanced Comprehensive Engineering Services Limited | Manufacturing | 1999 |
| Advanced Dental Training Limited | Extraterritorial | 2009 |
| Advanced Oxford CIC | Administrative & support | 2017 |
| Advanced Sports Ltd | Arts & recreation | 2010 |
| Advanced Television Limited | Information & communication | 2000 |
| Advenio Global Limited | Wholesale & retail | 2020 |
| Adventure Technologies Ltd | Information & communication | 2025 |
| Aegis Medical Solutions Limited | Education | 2025 |
| AEH Music Ltd | Information & communication | 2023 |
| Aenigmai LLP | | 2026 |
| Aereo Pangea Limited | Administrative & support | 2022 |
| Aeriandi Limited | Information & communication | 2002 |
| Aero-Dynamique Limited | Professional & scientific | 2013 |
| Aerospace Support Ltd | Transport & logistics | 1992 |
| Aerosyn AI Ltd | Information & communication | 2025 |
| Aesthetic Dermistry Limited | Health & social care | 2026 |
| Aether Limited | Professional & scientific | 2008 |
| Aethoris Ltd | Wholesale & retail | 2025 |
| Aethros Space Ltd | Information & communication | 2025 |
| AF Oxford Limited | Hospitality | 2019 |
| AFA Developments Ltd | Construction | 2018 |
| Afbe Limited | Information & communication | 2013 |
| Affinity Drug Design Limited | Health & social care | 2013 |
| Affordable Ltd | Information & communication | 2025 |
| Afghan Cuisine Marston Ltd | Hospitality | 2024 |
| Afghan Cuisine Oxford Limited | Hospitality | 2024 |
| Afghanistan-Turks Solidarity Organisation Ltd | Education | 2026 |
| Aflah and Co Ltd | Education | 2014 |
| Afreaka Aerials LLP | | 2013 |
| Africa Book Centre Limited | Wholesale & retail | 1989 |
| African Books Collective Limited | Administrative & support | 1989 |
| African Families in the UK (Afiuk) CIC | Education | 2015 |
| Afrimaster Ltd | Wholesale & retail | 2026 |
| Afro-Caribbean Grill Ltd | Hospitality | 2023 |
| Afrochichairsalon Ltd | Other services | 2026 |
| Afry Management Consulting Limited | Professional & scientific | 1991 |
| AFZ Electrical Services Ltd | Construction | 2021 |
| AG Spotless Services Limited | Transport & logistics | 2019 |
| Ageless Beauty Aesthetics Limited | Other services | 2023 |
| Agency Games Ltd | Information & communication | 2025 |
| Agent Print Limited | Manufacturing | 1996 |
| Aghosham Limited | Hospitality | 2026 |
| Agile Collective Ltd | Information & communication | 2011 |
| Agile Properties Ltd | Real estate | 2020 |
| Agilis Strategic Limited | Professional & scientific | 2004 |
| AGL Assistance Ltd | Professional & scientific | 2022 |
| Agnr Medics Limited | Health & social care | 2017 |
| AGO Construction Ltd | Construction | 2021 |
| Agrocultures Ltd | Wholesale & retail | 2025 |
| AGS Properties (Oxford) Limited | Real estate | 2010 |
| AGT Performance Ltd | Professional & scientific | 2026 |
| AGT Scenery Ltd | Manufacturing | 2025 |
| Agte Construction Ltd | Construction | 2020 |
| AH Energy and Planning Consultancy Ltd | Information & communication | 2013 |
| Ahama Property Limited | Real estate | 2018 |
| AHI ANI Limited | Other services | 2023 |
| Ahmeys Investments Ltd | Construction | 2016 |
| Ahmson Limited | Professional & scientific | 2013 |
| AHN Oxford Properties Ltd | Real estate | 2024 |
| AI Applications Limited | Wholesale & retail | 2025 |
| AI Invest LLP | | 2021 |
| AI Oxford Invest Ltd | Real estate | 2023 |
| AI Oxford Ltd | Manufacturing | 2018 |
| AI Springboard Ltd | Information & communication | 2026 |
| AI2 Solutions Ltd | Information & communication | 2021 |
| Aids Impact | Health & social care | 1993 |
| AIHEALTHCARE24 Ltd | Health & social care | 2024 |
| Aikoa Limited | Professional & scientific | 2023 |
| AIM Oxford Ltd | Information & communication | 2024 |
| Aimist Limited | Manufacturing | 2025 |
| Aiphoria Limited | Information & communication | 2023 |
| Air Cooled Engineering Limited | Wholesale & retail | 2006 |
| Airbnb Oxford Cleaning Limited | Administrative & support | 2025 |
| Airbus Helicopters UK Limited | Manufacturing | 1974 |
| Airmonk Ltd | Information & communication | 2025 |
| Aishini Properties Limited | Real estate | 2021 |
| Aisle Hire IT Ltd | Wholesale & retail | 2026 |
| Aitch & P Limited | Hospitality | 2007 |
| Aitchison Evans Consulting Limited | Professional & scientific | 2025 |
| AJ the Coach Ltd | Arts & recreation | 2025 |
| AJ Transfer Ltd | Financial services | 2024 |
| Ajax Unique Solutions Limited | Administrative & support | 2020 |