| Albany Land Ltd | Real estate | 2018 |
| Alberti Medical Limited | Health & social care | 2017 |
| Albetta Creation Limited | Wholesale & retail | 1999 |
| Aldenham Leisure Facilities Limited | Wholesale & retail | 1971 |
| Aldgate Consultants Limited | Real estate | 2025 |
| Aldwin Ltd | Professional & scientific | 2026 |
| Alex Cochrane Architects Limited | Professional & scientific | 2016 |
| Alex Ramsden Professional Services Ltd | Health & social care | 2021 |
| Alex Witney Ltd | Hospitality | 2026 |
| Alexa Services Ltd | Other services | 2024 |
| Alfred Broadband Limited | Information & communication | 2025 |
| Alfred Cover Limited | Financial services | 2025 |
| Alfred Electricity & GAS Limited | Energy | 2025 |
| Alfred Mobile Limited | Information & communication | 2026 |
| Alfred Wholesale Limited | Information & communication | 2025 |
| ALI Peppers Ltd | Hospitality | 2025 |
| Alis Witney Ltd | Hospitality | 2023 |
| Alison Dyer Limited | Professional & scientific | 2007 |
| Alisons Lane (Aston Tirrold) Management Company Limited | Households | 2021 |
| ALL Electrical Distributors Limited | Wholesale & retail | 2005 |
| ALL in 1 Engineering Limited | Professional & scientific | 2022 |
| ALL Knowing Ltd | Administrative & support | 2020 |
| All-Floors of Oxfordshire Ltd. | Wholesale & retail | 2000 |
| Allen & Kennerley Limited | Administrative & support | 2009 |
| Allfloors of Witney Ltd | Wholesale & retail | 2009 |
| Allota Futureland Limited | Information & communication | 2021 |
| Alocasia Careers Ltd | Administrative & support | 2023 |
| Alpha Brickwork Ltd | Construction | 2009 |
| Alpha BUS Company Limited | Transport & logistics | 2006 |
| Alpha Image (HD) Ltd | Manufacturing | 2003 |
| Alpha K9 Group Ltd. | Other services | 2020 |
| Alpha Kaye Construction Management Limited | Professional & scientific | 2025 |
| Alpha Publishing Ltd | Information & communication | 2014 |
| Alpha Records Limited | Information & communication | 2014 |
| Alpha Security Patrols Limited | Administrative & support | 2016 |
| Alter Eco Communications Ltd | Professional & scientific | 2011 |
| Alternative Comms Limited | Information & communication | 2014 |
| Alternative Communication Systems Limited | Information & communication | 2014 |
| Altius Live Limited | Professional & scientific | 2016 |
| Altius Sports Limited | Professional & scientific | 2011 |
| Altruva Healthcare Solutions Ltd | Health & social care | 2025 |
| AM Estate Agents Sales Ltd | Real estate | 2024 |
| Amanda Marks HR Limited | Professional & scientific | 2020 |
| AMB14 Limited | Professional & scientific | 2014 |
| Ambassadoor Industrial Doors Ltd | Construction | 2025 |
| Amber Financial Management Ltd | Professional & scientific | 2008 |
| Ambic Equipment Limited | Manufacturing | 1978 |
| Ambient Estates Ltd | Real estate | 2026 |
| Ambring Property Empire Ltd | Real estate | 2018 |
| AMC Build Limited | Construction | 2013 |
| Amchil Construction Limited | Construction | 2021 |
| Amec Groundworks Limited | Construction | 2017 |
| American Pizza Witney Limited | Hospitality | 2023 |
| Amesplan Ltd | Wholesale & retail | 2013 |
| Amey Kirk & Barolo Properties Ltd | Real estate | 2024 |
| Amey Kirk Properties Ltd | Real estate | 2020 |
| AMI Media Ltd | Information & communication | 2022 |
| Amiantus Environmental Consultants Limited | Professional & scientific | 2005 |
| Amiantus Holdings Ltd | Professional & scientific | 2019 |
| Amica Corporate Finance Limited | Financial services | 2024 |
| Amies Engineering Limited | Wholesale & retail | 2016 |
| Amin IB Limited | Wholesale & retail | 2026 |
| Amlepartners Limited | Real estate | 2013 |
| Amritsadhana Ltd | Professional & scientific | 2024 |
| Amsel Tech Ltd | Professional & scientific | 2014 |
| AMX Academy Ltd | Education | 2026 |
| ANA Titcombe Design Limited | Professional & scientific | 2026 |
| Anabro Properties Ltd | Hospitality | 2024 |
| Anacut Developments Limited | Real estate | 1962 |
| Anaesthesia Solutions Limited | Health & social care | 2023 |
| Analyticore Consulting Limited | Information & communication | 2023 |
| Anasad Cleaning Services Ltd | Administrative & support | 2024 |
| Anasad Logistics Limited | Transport & logistics | 2024 |
| Anderson & Anderson Family Holdings Ltd | Financial services | 2026 |
| Anderson + Anderson Accountancy Services Ltd | Professional & scientific | 2021 |
| Anderson Clinic Limited | Other services | 2016 |
| Anderson Equity Holdings Limited | Financial services | 2026 |
| Anderson ORR Architects Limited | Professional & scientific | 2005 |
| Anderson ORR Capital Limited | Professional & scientific | 2014 |
| Anderson ORR Consulting Limited | Professional & scientific | 2019 |
| Anderson ORR Group Limited | Financial services | 2018 |
| Anderson Thoren Ltd | Professional & scientific | 2024 |
| Andover Forensics Limited | Information & communication | 2024 |
| Andrew a Adams and Co Ltd | Professional & scientific | 2008 |
| Andrew and Christopher Goodfellow Limited | Extraterritorial | 2025 |
| Andrew Bird Associates Limited | Professional & scientific | 2013 |
| Andrew Dore Holding’S Ltd | Real estate | 2025 |
| Andrew Holborough Builders Limited | Construction | 2003 |
| Andrew Silley - Independent Energy Specialist Ltd | Administrative & support | 2022 |
| Andrew Smith Commercial Practice Limited | Professional & scientific | 2008 |
| Andrews Duckett Ltd | Professional & scientific | 2025 |
| Andy's Life Skills Limited | Real estate | 2014 |
| Anevate Ltd | Professional & scientific | 2018 |
| Angel House Estates Limited | Real estate | 2025 |
| Anglican Mainstream | Other services | 2005 |
| Anglo Svenska Motor Sport Marketing Limited | Professional & scientific | 2009 |
| ANH Beauty Limited | Other services | 2018 |
| Anima Medica Ltd | Health & social care | 2025 |
| Animus Modelling Ltd | Professional & scientific | 2025 |
| Animus Surgical Limited | Wholesale & retail | 2002 |