| Anker-Aero Ltd | Professional & scientific | 2017 |
| Anne Armitage Limited | Health & social care | 2022 |
| ANT Couriers Ltd | Transport & logistics | 2020 |
| Antbella Limited | Professional & scientific | 2019 |
| Anyrisks Ltd | Information & communication | 2024 |
| Anything BUT Chardonnay Ltd | Professional & scientific | 2026 |
| AOR Holdings Limited | Financial services | 2019 |
| Aoraki Consulting Limited | Professional & scientific | 2024 |
| Apax Engineering Consultancy Limited | Construction | 2023 |
| APC Success Limited | Professional & scientific | 2010 |
| APC3 Limited | Real estate | 2025 |
| Apex Estate Management (Cotswolds) Limited | Households | 2025 |
| Apex Hardscaping Ltd | Construction | 2026 |
| APH Associates Ltd | Professional & scientific | 2008 |
| Apli Construction Ltd | Construction | 2011 |
| Apple & Dreamland Limited | Wholesale & retail | 2007 |
| Applegarth Court Management Co Limited | Households | 2018 |
| Appleton Groundworks & Construction Ltd | Construction | 2025 |
| Applied Insights (Consulting) Ltd | Professional & scientific | 2021 |
| Aprais Limited | Information & communication | 2000 |
| Aquarius Plumbing Ltd | Construction | 2005 |
| Aqueous Solutions Limited | Professional & scientific | 2007 |
| Aquila Visum Ltd | Manufacturing | 2011 |
| Arab World Ministries | Other services | 1996 |
| Arbor Homes Oxford Limited | Real estate | 2011 |
| Archer Family Limited | Financial services | 2021 |
| Archi Consultancy Ltd | Professional & scientific | 2024 |
| Architecting Solutions Ltd | Information & communication | 2013 |
| Archive Innovation Limited | Financial services | 2021 |
| Archon Security Ltd | Information & communication | 2013 |
| Arda Brickwork Ltd | Construction | 2023 |
| Arda Rentals Ltd | Real estate | 2024 |
| Arden Holdco Limited | Financial services | 2025 |
| Ardorvis Technology Limited | Manufacturing | 2008 |
| Aree Commerce UK Ltd | Wholesale & retail | 2023 |
| Arete Advisory Limited | Professional & scientific | 2025 |
| Argantrix Limited | Professional & scientific | 2014 |
| Argyll Stonework Ltd | Manufacturing | 2019 |
| ARI Consultancy Limited | Financial services | 2001 |
| ARK SPV Limited | Real estate | 2020 |
| Arkgeist Limited | Real estate | 2026 |
| Arkitectonica Ltd | Construction | 2024 |
| Arlington ROW Ltd | Hospitality | 2023 |
| Armstrong Bookkeeping Ltd | Professional & scientific | 2020 |
| Arqworks Ltd | Information & communication | 2016 |
| Arucas Ltd | Other services | 2016 |
| Aryan Composites Limited | Professional & scientific | 2008 |
| ASB Roofing Ltd | Construction | 2017 |
| Asbestox Ltd | Professional & scientific | 2025 |
| ASD Arts and Education Ltd. | Information & communication | 2018 |
| ASH & Ally Ltd | Real estate | 2025 |
| Ashcroft and Rayner Consulting Limited | Real estate | 2005 |
| Ashdown Tree Management Limited | Administrative & support | 2022 |
| Ashfold Management Services Limited | Professional & scientific | 2013 |
| Ashford Consultancy Services Ltd | Information & communication | 2017 |
| Ashleigh Clarke Architects Limited | Professional & scientific | 2020 |
| Asia Chinese Takeaway Ltd | Hospitality | 2023 |
| Asia West Group Limited | Professional & scientific | 2014 |
| Asia West Management Services Limited | Professional & scientific | 2016 |
| ASK William Limited | Administrative & support | 2020 |
| ASL Automotive Limited | Wholesale & retail | 2017 |
| Aspect Plumbing & Heating (Witney) Limited | Construction | 2006 |
| Aspirational Developments Limited | Extraterritorial | 2024 |
| Aspire Sport and Coaching Ltd | Education | 2026 |
| Aspm Solutions Ltd | Professional & scientific | 2018 |
| Assist Auditing & Training Services Limited | Professional & scientific | 2014 |
| Associated Agencies Limited | Manufacturing | 1993 |
| Associated Blinds Ltd. | Construction | 1997 |
| Asta Piante Ltd | Extraterritorial | 2007 |
| Astack Building Ltd | Construction | 2019 |
| Asthall & Co. Ltd | Professional & scientific | 2025 |
| Asthally Limited | Agriculture & fishing | 1992 |
| Aston & James Office Supplies Limited | Wholesale & retail | 2012 |
| AT & BMG Investment (UK) Limited | Real estate | 2020 |
| AT Global Holdings Limited | Financial services | 2019 |
| AT Horses Family Assets (UK) Limited | Real estate | 2016 |
| ATA Europe Ltd | Administrative & support | 2022 |
| Athena Anpr Limited | Administrative & support | 2006 |
| Athletic Vision Limited | Wholesale & retail | 2025 |
| Atkin, Grant and Lang Limited | Manufacturing | 1984 |
| Atkinson Creative Ltd | Professional & scientific | 2017 |
| Atlantic Financial Solutions Limited | Professional & scientific | 2008 |
| Atlantis Residences Limited | Real estate | 2017 |
| Atomic Cards Limited | Wholesale & retail | 2024 |
| Attack Golf Limited | Arts & recreation | 2013 |
| ATV Global Limited | Financial services | 2020 |
| Auberge Inns Ltd | Hospitality | 2019 |
| Auchencairn Forest LLP | | 2015 |
| Audere Consulting Limited | Professional & scientific | 2013 |
| Audley Travel Group Limited | Administrative & support | 1996 |
| Audley Travel Services Limited | Administrative & support | 2019 |
| Austen Aviation Services Limited | Construction | 2007 |
| Austen Dawson (Construction and Mechanical) Limited | Construction | 2022 |
| Austen Fabrication Limited | Manufacturing | 2012 |
| Austin Drive (Coventry) Limited | Real estate | 2026 |
| Auto Concepts Limited | Administrative & support | 2011 |
| Auto Transmissions Ltd | Extraterritorial | 1999 |
| Auto Tyre Services Limited | Wholesale & retail | 2003 |
| Autobead Ltd | Wholesale & retail | 2015 |
| Autocare Express (Witney) Limited | Wholesale & retail | 2001 |