| AQ Estates Limited | Real estate | 2000 |
| AQ Ventures Ltd | Wholesale & retail | 2026 |
| Aqua Blue Design Limited | Manufacturing | 2003 |
| Aqua Robson Care Ltd | Health & social care | 2020 |
| Aqua Warehouse Limited | Other services | 2003 |
| Aquaclean Limited | Administrative & support | 1996 |
| Aquavale Limited | Professional & scientific | 1998 |
| Aquila Consultants Limited | Information & communication | 1998 |
| AR515 Ltd | Health & social care | 2024 |
| Arabella Manning Legal Services Limited | Professional & scientific | 2022 |
| Araknus Ltd | Wholesale & retail | 2025 |
| Aranks Opulent Limited | Real estate | 2024 |
| Arben Services Ltd | Manufacturing | 2014 |
| Arbient Limited | Health & social care | 2025 |
| Arbor Trading Limited | Wholesale & retail | 1988 |
| ARC Audio Visual & IT Solutions Limited | Administrative & support | 2002 |
| ARC Commercial Management Services Limited | Professional & scientific | 2000 |
| ARC Facilities and Security Ltd | Administrative & support | 2025 |
| ARC Training (UK) Limited | Education | 2002 |
| Arcese Real Estate UK Limited | Real estate | 2006 |
| Arch Electrical Company Limited | | 1987 |
| Archer Windows Limited | Construction | 2000 |
| Archi Firm Ltd | Professional & scientific | 2025 |
| Archillion UK Ltd | Construction | 2006 |
| Archmedic Ltd | Health & social care | 2024 |
| Archway Estate Limited | Real estate | 2023 |
| Arconvale Limited | Professional & scientific | 1991 |
| Arctirion UK Ltd | Extraterritorial | 2026 |
| Aria Living Limited | Health & social care | 2026 |
| Ariello Ltd | Professional & scientific | 2025 |
| Arif Hossain Ltd | Wholesale & retail | 2026 |
| Arivista Limited | Real estate | 2006 |
| ARK Formation Limited | Professional & scientific | 2018 |
| Arkley Limited | Construction | 2003 |
| Armaa Limited | Wholesale & retail | 2023 |
| Arman UK Production Limited | Wholesale & retail | 2026 |
| Armour Roofing Services London Limited | Construction | 2025 |
| Armstrong Builders' Services Limited | | 1990 |
| Arola IT Ltd | Information & communication | 2017 |
| Aromachina Limited | Hospitality | 2021 |
| Aroona Atif Ltd | Wholesale & retail | 2025 |
| Arosashop Trading Limited | Wholesale & retail | 2023 |
| Arpm Limited | Real estate | 2023 |
| Arrisa Property Ltd | Real estate | 2021 |
| Arrivalstar Limited | Professional & scientific | 2018 |
| Arrow Properties Essex Ltd. | Construction | 2006 |
| Arrow Stairs Limited | Wholesale & retail | 1990 |
| Arrow Tools (UK) Limited | Manufacturing | 1992 |
| Arsendo Consultant Ltd | Wholesale & retail | 2023 |
| ART2PART Limited | Professional & scientific | 2000 |
| Artbyusuf Limited | Wholesale & retail | 2024 |
| Artesian (London) Limited | Other services | 1996 |
| Arthur Security Services Ltd | Administrative & support | 2006 |
| Arti Creations Investments Limited | Hospitality | 2005 |
| Artless Cornerstone Ltd | Professional & scientific | 2019 |
| ARV Digital Ltd | Professional & scientific | 2026 |
| Arwindersingh Ltd | Information & communication | 2025 |
| Arya Dine Ltd | Hospitality | 2026 |
| AS Budul Ltd | Manufacturing | 2025 |
| AS7 Consultancy Ltd | Arts & recreation | 2023 |
| ASA Invest Limited | Real estate | 2022 |
| ASA Luxe Ltd | Administrative & support | 2024 |
| Asaman & Co Accountants Ltd | Professional & scientific | 2016 |
| Asaros Ltd | Wholesale & retail | 2026 |
| Asarsian Ltd | Wholesale & retail | 2025 |
| Asase Tree Ltd | Manufacturing | 2018 |
| ASC Worldwide Limited | Real estate | 2003 |
| Asem Childcare Ltd | Education | 2016 |
| ASH Hill Properties Limited | Construction | 2004 |
| ASH Medical Consulting Limited | Health & social care | 2020 |
| ASH Valley Property Limited | Real estate | 2008 |
| Ashadur Investments Ltd | Real estate | 2019 |
| Ashbarn Limited | Construction | 1997 |
| Ashburnham Insurance Services Limited | Financial services | 1995 |
| Ashburton Building Ltd | Construction | 2006 |
| Ashburton Electrics Limited | Construction | 1987 |
| Ashdon Centre LLP | | 2023 |
| Ashfaq Goods Limited | Wholesale & retail | 2026 |
| Ashingdon Gardens (Block J) Management Company Limited | Real estate | 1991 |
| Ashingdon Gardens (Block K) Management Company Limited | Real estate | 1992 |
| Ashingdon Gardens (Block M) Management Company Limited | Real estate | 1993 |
| Ashingdon Gardens (Block O) Management Company Limited | Real estate | 1993 |
| Ashingdon Pre-School Limited | Education | 1999 |
| Ashiru Forensic Toxicology Limited | Professional & scientific | 2026 |
| Ashley Bodimeade Services Limited | Wholesale & retail | 2005 |
| Ashley White Estates Ltd | Real estate | 2004 |
| Ashlyns Catering Limited | Wholesale & retail | 2005 |
| Ashutosh Kapoor Limited | Health & social care | 2025 |
| Ashwed Limited | Construction | 1998 |
| Ashwood Contracts Limited | Construction | 2004 |
| Ashwyk Limited | Professional & scientific | 1990 |
| Asim Leatherwear Ltd | Wholesale & retail | 2001 |
| Asiyan Limited | Hospitality | 2020 |
| ASK Hotels Ltd | Hospitality | 2015 |
| Askoe Building Services Limited | Construction | 2000 |
| Aslakr Park Management Company Limited | Households | 2017 |
| Aspect Contracts (Asbestos) Limited | Administrative & support | 1987 |
| Aspen Vets Ltd | Professional & scientific | 2006 |
| Asperula Limited | Wholesale & retail | 2005 |
| Aspiring Future Minds Ltd | Education | 2025 |