| Asaset Group Ltd | Professional & scientific | 2022 |
| Ascend Wellness Ltd | Health & social care | 2024 |
| Ascendia Partners Ltd | Education | 2026 |
| Ascension Earth Resources Ltd | Mining & quarrying | 2024 |
| Ascent Construction Limited | Construction | 2010 |
| Ascentia Holdings Limited | Administrative & support | 2023 |
| Ascott Manor Limited | Professional & scientific | 2024 |
| Aseillumination Ltd | Financial services | 2025 |
| Ases Consulting Ltd | Information & communication | 2015 |
| ASH Residential Property Management Limited | Real estate | 2005 |
| Ashcraft Limited | Real estate | 2014 |
| Ashcroftworks Ltd | Information & communication | 2025 |
| Ashdene Care Services Ltd | Health & social care | 2017 |
| Ashey Haulage & Recruiting Ltd | Transport & logistics | 2022 |
| Ashford Riverside Park Limited | Construction | 2016 |
| Ashira Foods Ltd | Wholesale & retail | 2025 |
| Ashley Court Management Company Limited | Households | 1988 |
| Ashline Group Limited | Financial services | 2026 |
| Ashline Limited | Professional & scientific | 2012 |
| Ashly Ltd | Hospitality | 2020 |
| Ashok Design Consultancy Ltd | Professional & scientific | 2025 |
| Ashtar Publi Limited | Information & communication | 2014 |
| Ashvalley Ltd | Professional & scientific | 1998 |
| Asif Group Ltd | Financial services | 2026 |
| Asif Hameed Limited | Information & communication | 2025 |
| Asiic UK Ltd | Wholesale & retail | 2022 |
| ASJ Johnson Group Limited | Transport & logistics | 2025 |
| ASK2 Company Ltd | Financial services | 2023 |
| ASL Zorb Mania Ltd | Arts & recreation | 2024 |
| Asmiz Ltd | Hospitality | 2025 |
| Aspect Developments (Oxford) Limited | Construction | 2010 |
| Aspen Insights Limited | Professional & scientific | 2023 |
| Aspire &Thrive Support Services Ltd | Health & social care | 2025 |
| Aspire Enterprise Services Limited | Extraterritorial | 2018 |
| Aspire Globe Limited | Education | 2024 |
| Aspire Oxford Medical Limited | Health & social care | 2019 |
| Aspire Oxfordshire Community Enterprise Ltd. | Administrative & support | 2001 |
| Aspr-R Ltd | Wholesale & retail | 2024 |
| ASR Tech Ltd | Extraterritorial | 2010 |
| Assembly of GOD Ministry GOD IS Faithful Ltd | Education | 2022 |
| Assessment Technologies Limited | Information & communication | 2020 |
| Assessprogress.Com Ltd | Education | 2022 |
| Asset & Project Finance Ltd | Financial services | 2018 |
| Asset Heritage Consulting Ltd | Professional & scientific | 2011 |
| Assistnow Ltd | Construction | 2024 |
| Association of Quality Control in Education and Teaching | Education | 2013 |
| Associative Limited | Information & communication | 2025 |
| Assongu Tradings Ltd | Wholesale & retail | 2019 |
| Assumption-Truth Limited | Professional & scientific | 2009 |
| Astana Real Estate Ltd | Real estate | 2024 |
| Aston Clinton Land Ltd | Real estate | 2014 |
| Astor Care Limited | Health & social care | 1989 |
| Astor Care Tickets Limited | Arts & recreation | 2015 |
| Astounding Props Limited | Information & communication | 2023 |
| Astra Diligence Ltd | Professional & scientific | 2021 |
| Astrum Enterprises LLP | | 2012 |
| Astute Outcomes Limited | Health & social care | 2025 |
| Asunny Circuits Limited | Wholesale & retail | 2024 |
| ASW995 Ltd | Wholesale & retail | 2025 |
| Asylum Welcome | Information & communication | 2002 |
| ASZ Interests Limited | Real estate | 2020 |
| AT - Anything Anytime Ltd | Construction | 2025 |
| AT Gold Card Limited | Extraterritorial | 1998 |
| AT My Table Limited | Professional & scientific | 2011 |
| Atanto Limited | Information & communication | 2014 |
| Ates Real Estate Limited | Hospitality | 2023 |
| ATG Oxford Limited | Extraterritorial | 1998 |
| ATH Software Services Ltd | Information & communication | 2019 |
| Athena Global Education Ltd | Education | 2020 |
| Athena Oxford Ltd | Hospitality | 2015 |
| Athinka Limited | Professional & scientific | 2009 |
| Athleat UK Limited | Wholesale & retail | 2012 |
| Athletic Edge Performance Limited | Construction | 2016 |
| Athletic Football Group Ltd | Arts & recreation | 2024 |
| Athletic Performance Club Ltd | Health & social care | 2024 |
| Athletic Technology Company Limited | Manufacturing | 2019 |
| Atif Store Ltd | Wholesale & retail | 2019 |
| Atija Property Ltd | Real estate | 2023 |
| Atkinson Energy Limited | Professional & scientific | 2024 |
| Atkinson Engineering Limited | Professional & scientific | 2007 |
| Atlantic Fish Bar (Oxford) Ltd | Hospitality | 2023 |
| Atlantic Harbour Limited | Information & communication | 2005 |
| Atlantic Imaging Limited | Wholesale & retail | 2013 |
| Atlantic.Net UK Cloud Limited | Information & communication | 2015 |
| Atlas Culture Ltd | Information & communication | 2026 |
| Atlas Medical Publishing Limited | Information & communication | 2002 |
| Atlas Oxford Ltd | Hospitality | 2018 |
| Atlas Ridge Limited | Financial services | 2025 |
| Atlaswise Limited | Information & communication | 2024 |
| Atmos Comms Group Limited | Administrative & support | 2024 |
| Atmos Comms Limited | Administrative & support | 2021 |
| Atom Tax & Legal Accounting Services Ltd | Professional & scientific | 2023 |
| Atomic Bidco 1 Limited | Financial services | 2025 |
| Atomic Financial Limited | Financial services | 2014 |
| Atomic Holdco 1 Limited | Financial services | 2025 |
| Atomic Holdco 2 Limited | Financial services | 2025 |
| Atomic Midco 1 Limited | Financial services | 2025 |
| Atomic Midco 2 Limited | Financial services | 2025 |
| Atomic Sauces Ltd | Wholesale & retail | 2020 |
| Atomic Theatre Community Interest Company | Arts & recreation | 2019 |