| Airship Services Limited | Information & communication | 2001 |
| Airside Enterprises Ltd | Financial services | 2025 |
| Airside Investments Ltd | Financial services | 2015 |
| AISLE44 Limited | Arts & recreation | 2024 |
| Aistetic Limited | Information & communication | 2019 |
| Aitech Point Ltd | Information & communication | 2025 |
| AJ Racing Ltd | Professional & scientific | 2021 |
| AJD Beamlines Ltd | Professional & scientific | 2025 |
| AK Design Atelier Limited | Professional & scientific | 2022 |
| Akal Sahai Construction Ltd | Construction | 2025 |
| AKP Consult Ltd | Information & communication | 2019 |
| Akru Solutions Limited | Information & communication | 2023 |
| AL6060 Ltd | Administrative & support | 2023 |
| Alan Ryder Investments Limited | Real estate | 2002 |
| Alan Wallis Farming Limited | Agriculture & fishing | 2017 |
| ALB LOGISTICS11 Ltd | Transport & logistics | 2025 |
| ALB Technologies Limited | Financial services | 2017 |
| Albionweave Limited | Wholesale & retail | 2025 |
| Alder Care Ltd | Health & social care | 2022 |
| Alder Demain & Akers Limited | Professional & scientific | 2013 |
| Alek Transport Ltd | Transport & logistics | 2019 |
| Alesani Ltd | Education | 2022 |
| Alessi Motors Ltd | Wholesale & retail | 2024 |
| Alethio Therapeutics Limited | Professional & scientific | 2021 |
| Alexander Boys Design Ltd | Professional & scientific | 2025 |
| Alexrus Care Solutions Limited | Health & social care | 2019 |
| Alfresco Group Ltd | Administrative & support | 2008 |
| ALI Martin Global Limited | Administrative & support | 2011 |
| Alison Webb Limited | Administrative & support | 2023 |
| Alistair Batey Television Limited | Information & communication | 2011 |
| Alivero Limited | Professional & scientific | 2000 |
| Alkebulan the Mother of Mankind Limited | Wholesale & retail | 2025 |
| ALL Aboard Opera! Ltd | Arts & recreation | 2021 |
| ALL Days Property Ltd | Real estate | 2025 |
| ALL Labels Limited | Professional & scientific | 2000 |
| ALL OUR Gods Limited | Arts & recreation | 2017 |
| Allen Plumbing and Heating Services Limited | Construction | 2012 |
| Allenway Ltd | Real estate | 2013 |
| Allison Garfield Ltd | Professional & scientific | 2021 |
| Allmakes PR2 4X4 Limited | Wholesale & retail | 1986 |
| Allsports Trophies Limited | Manufacturing | 2003 |
| Alpha Bagel Corporation Ltd | Professional & scientific | 2019 |
| Altenberg Ltd | Transport & logistics | 2016 |
| Alternative Energy Solutions Limited | Construction | 2010 |
| Altom Tree Care Ltd | Other services | 2001 |
| Altomyra Limited | Arts & recreation | 2020 |
| Always Home Limited | Real estate | 2001 |
| AM Healthcare Group Limited | Professional & scientific | 2023 |
| Amano Enzyme Europe Limited | Wholesale & retail | 1992 |
| Amar Property Management Limited | Hospitality | 2022 |
| Amaranthlabs Ltd | Manufacturing | 2024 |
| Amber Office Support Ltd | Administrative & support | 2023 |
| Ambient Sky Ltd | Transport & logistics | 2021 |
| AMC Geep Limited | Manufacturing | 2021 |
| American Immigration Services Ltd | Other services | 2024 |
| American Jukebox Limited | Arts & recreation | 2005 |
| Amey Leisure Limited | Professional & scientific | 2017 |
| Amida Travel Ltd | Administrative & support | 2022 |
| Amity Holdings Limited | Financial services | 1998 |
| Amity Insulation Services Limited | Construction | 1985 |
| Amot & Ekalb Limited | Information & communication | 2018 |
| Amot & Remmus Ltd | Professional & scientific | 2015 |
| Ampleton Group Ltd | Financial services | 2017 |
| Amrit & Brother Limited | Administrative & support | 2023 |
| AN Dyer Productions Ltd | Information & communication | 2023 |
| Ananta Learning Ltd | Professional & scientific | 2019 |
| Anatolia Web Services Ltd | Wholesale & retail | 2024 |
| Ancora Business Partners Ltd | Administrative & support | 2017 |
| Andrew Paul Consult Ltd | Professional & scientific | 2026 |
| Andrew Tinkler Bloodstock Limited | Arts & recreation | 2011 |
| Andy Bryan Builders Limited | Construction | 2024 |
| Andy Lawal Ltd | Health & social care | 2016 |
| Angela Adams Consulting Ltd | Professional & scientific | 2018 |
| Aniko Rendek Ltd | Health & social care | 2023 |
| Anivan Cleaning Limited | Administrative & support | 2024 |
| Ankail Property Limited | Real estate | 2024 |
| Annabel's World Limited | Arts & recreation | 2023 |
| Anoja Business Development Ltd | Professional & scientific | 2014 |
| Another Hemisphere Limited | Professional & scientific | 2025 |
| Anthony Tory Limited | Professional & scientific | 2006 |
| Antique Newspapers Limited | Wholesale & retail | 2021 |
| Apiary Botanicals Limited | Extraterritorial | 2026 |
| Apis Mellifera Cosmetics Limited | Extraterritorial | 2025 |
| Apos Care Ltd | Public administration | 2021 |
| App Innovation Ltd | Information & communication | 2025 |
| Applecroft Services Ltd | Professional & scientific | 2018 |
| Appleton Community Shop Limited | Wholesale & retail | 2000 |
| Appleton House Limited | Real estate | 2025 |
| Appleton Medical Communications Ltd | Administrative & support | 2020 |
| Applied Systems (Oxford) Limited | Information & communication | 1988 |
| APS Solutions Ltd | Other services | 2025 |
| APT 10 Entertainment Ltd | Arts & recreation | 2021 |
| Aptuit (Oxford) Limited | Manufacturing | 2011 |
| Aquaterra International Limited | Administrative & support | 2001 |
| AR Hughes Ltd | Administrative & support | 2023 |
| Arboriculture Plant Hire Limited | Other services | 2022 |
| Archadia (UK) Limited | Professional & scientific | 2014 |
| Archo Consulting Ltd | Professional & scientific | 2019 |
| Arcminute Expressions Ltd | Education | 2023 |
| Arco Cyber Ltd | Information & communication | 2022 |