| Apollo Trading Limited | Wholesale & retail | 1994 |
| Apple Barn Services Limited | Extraterritorial | 2002 |
| Appleby Developments Limited | Construction | 1958 |
| Appledore Turkeys Limited | Agriculture & fishing | 2008 |
| Apricus Ventures Limited | Real estate | 2022 |
| APS Properties (PVT) Ltd | Real estate | 2015 |
| APT Heating & Plumbing Limited | Construction | 2006 |
| Apulia Blend Ltd | Wholesale & retail | 2006 |
| Aqua Damp (London) Limited | | 1986 |
| Aqua Health& Beauty Ltd | Wholesale & retail | 2020 |
| Aquabatix Limited | Arts & recreation | 2005 |
| Aqualisa Finance Ltd | Financial services | 2004 |
| Aqualisa Group Ltd | Financial services | 2004 |
| Aqualisa Products Limited | Manufacturing | 1976 |
| AR Capital LP | | 2014 |
| AR Car Wash Limited | Administrative & support | 2024 |
| Arberforth Developments Limited | Construction | 2007 |
| Arberforth Ltd | Real estate | 2007 |
| Arcalaudis Limited | Financial services | 2005 |
| Arcarius Developments Limited | Construction | 2003 |
| Archbrook Property Services Ltd | Real estate | 2017 |
| Archer Contracts Limited | Construction | 1993 |
| Archer Daniels Midland (UK) Limited | Wholesale & retail | 1973 |
| Archers Television Service Ltd. | Other services | 1992 |
| Architectural Services Kent Ltd | Professional & scientific | 2004 |
| Ardel Concepts Limited | Information & communication | 2007 |
| Ardevo Beheer Limited | Administrative & support | 2007 |
| Ardo UK Limited | Manufacturing | 1970 |
| Area Network Accountants Limited | Professional & scientific | 2001 |
| Arena Park Construction Limited | Construction | 1985 |
| Argabond Limited | | 1980 |
| Argee Limited | Administrative & support | 2004 |
| Aridi Invest Ltd | Real estate | 2026 |
| Arkadia Limited | Professional & scientific | 2004 |
| Arni Dent Ltd | Health & social care | 2026 |
| Aroma Lounge Kent Ltd | Hospitality | 2023 |
| Aromoké Designs Ltd | Professional & scientific | 2021 |
| Aronella Limited | Other services | 2016 |
| Arren & Aneka Limited | Wholesale & retail | 2018 |
| Arrow Commissioning Ltd | Energy | 2016 |
| Art Force Limited | Wholesale & retail | 2017 |
| Art of Dance Limited | Arts & recreation | 2003 |
| Art of Iron Limited | Manufacturing | 1999 |
| Artco Construction Services Ltd | Construction | 2012 |
| Arte Bianca Ltd | Hospitality | 2007 |
| Artemis Scientific Communications Limited | Professional & scientific | 2007 |
| Arthurton Accountancy Services Limited | Professional & scientific | 2006 |
| Artisan Developments Limited | Administrative & support | 1997 |
| Artisan Flooring UK Ltd | Construction | 2005 |
| Arts, Crafts & Designs Marketing Centres Limited | | 1982 |
| Arwen Building Contractor Ltd | Professional & scientific | 2025 |
| Asco Space Planning Limited | Administrative & support | 1998 |
| ASH Technical Catering Limited | Manufacturing | 2008 |
| ASH Tree Court Residents Association Limited | Households | 1992 |
| ASH UK Consultants Ltd | Professional & scientific | 2024 |
| Ashford Cattle Market Company Limited(The) | Wholesale & retail | 1856 |
| Ashford Flexible Hose and Coupling Supplies Limited | Wholesale & retail | 1984 |
| Ashford Orbital Limited | Wholesale & retail | 2008 |
| Ashford Stratton Financial Planning Limited | Extraterritorial | 1992 |
| Ashford Tile Centre Limited | Transport & logistics | 2002 |
| Ashlake Properties Limited | Administrative & support | 1999 |
| Ashley Lawrence Ltd | Information & communication | 1998 |
| Ashman Consulting Limited | Information & communication | 2002 |
| Ashted Interiors Limited | Construction | 2001 |
| Ashwood Surfacing Ltd. | Construction | 1999 |
| ASK Esolutions Limited | Information & communication | 2019 |
| Asmera Limited | Hospitality | 2013 |
| Aspect Interiors Designs Limited | Administrative & support | 2003 |
| Aspenvale Limited | Wholesale & retail | 1978 |
| Aspinall & Aspinall Limited | Administrative & support | 2009 |
| Association of Casualty and Health Emergency Simulators | Health & social care | 1996 |
| Assra Limited | Arts & recreation | 1988 |
| Assyria Properties Limited | Real estate | 2021 |
| Astauto Limited | Professional & scientific | 1987 |
| Astell Scientific (Holdings) Limited | Professional & scientific | 1976 |
| Astell Scientific Limited | Manufacturing | 1950 |
| Asteven Global UK Ltd | Construction | 2021 |
| Astir Limited | Professional & scientific | 2003 |
| Astonstar Limited | Wholesale & retail | 1990 |
| ATAS4B Construction UK Ltd | Construction | 2021 |
| ATC Fencing Ltd | Construction | 2025 |
| Atcost Structures Limited | | 1961 |
| Atharvaretail Technology Ltd | Information & communication | 2024 |
| Athelbrae Limited | Professional & scientific | 2003 |
| Athena Flooring Company Limited | Construction | 2006 |
| Atkinsons Electrical Contractors Ltd | Administrative & support | 2005 |
| Atom GAS Ltd | Construction | 2017 |
| Attentus Group Ltd | Information & communication | 2007 |
| Audentia Consulting Ltd | Professional & scientific | 2018 |
| Audika Hearing Care Ltd | Wholesale & retail | 1986 |
| Auditors Limited | Extraterritorial | 1995 |
| Audleys Wood Hotel (NO. 2) Limited | Professional & scientific | 2008 |
| Aumento Limited | Professional & scientific | 2007 |
| Ausrowe Marketing Limited | Professional & scientific | 2000 |
| Austinoma Chemist Limited | Wholesale & retail | 2007 |
| Autofirm Limited | | 1985 |
| Automated Limited | Other services | 1997 |
| Automatic Business Communications (Croydon) Limited | Transport & logistics | 1984 |
| Automatica - UK Limited | Wholesale & retail | 2003 |
| Autowash (Domestic & Commercial Appliances) Limited | Manufacturing | 1996 |