| Allotria Productions Limited | Information & communication | 2005 |
| Allstore Solutions Limited | Transport & logistics | 2005 |
| Alltime Express Limited | Transport & logistics | 2005 |
| Allwood Flooring Installations Limited | Construction | 2000 |
| Almancil (UK) Ltd | Information & communication | 2008 |
| Alpawood Limited | | 1985 |
| Alpha and Omega Christian Seminary Limited | Education | 2025 |
| Alpha Beta PC Ltd | Professional & scientific | 2019 |
| Alpha Digitek Solutions Ltd | Professional & scientific | 2018 |
| Alpha Finance Services Limited | Professional & scientific | 2007 |
| Alpha Peak Property Investment Ltd | Real estate | 2022 |
| Alpha Preparatory School Limited | Education | 1948 |
| Alpha Private Car Hire Limited | Transport & logistics | 2003 |
| Alpha Projects Limited | Construction | 2025 |
| Alphalarch Limited | Real estate | 1997 |
| Alphaseven Omni-Solutions (UK) Limited | Professional & scientific | 2019 |
| Alsham Ltd | Real estate | 2016 |
| Altea Properties Limited | Real estate | 2022 |
| Althoff & Associates Ltd | Financial services | 2007 |
| Alwadi Food & Wine Limited | Wholesale & retail | 2026 |
| ALY Consulting Limited | Information & communication | 2007 |
| AM Construction Limited | Construction | 1998 |
| Am.Tec Electrical Services Limited | Energy | 1997 |
| Amadeus Events Limited | Administrative & support | 2003 |
| Amar Panesar Photography Limited | Professional & scientific | 2019 |
| Amax Fire and Security Limited | Construction | 2000 |
| Amazing Internet Limited | Information & communication | 2000 |
| Amazingkids.Com Limited | Education | 2007 |
| Amazon Business Consulting Limited | Professional & scientific | 1984 |
| Amazy Education Limited | Education | 2020 |
| Ambidextrous Design Limited | Professional & scientific | 2017 |
| Ambitions Fulfilled Limited | Other services | 2026 |
| Ambray Limited | Wholesale & retail | 2004 |
| Ambush Security Systems Limited | Administrative & support | 1998 |
| AMC (London) Limited | Financial services | 2006 |
| Amco Consultancy Limited | Professional & scientific | 2006 |
| American Beauty Bar Limited | Other services | 1986 |
| Amery Construction Limited | Administrative & support | 2000 |
| Amind Medical Ltd | Wholesale & retail | 2021 |
| Amoco Europe Limited | Professional & scientific | 1997 |
| Amoco U.K.Petroleum Limited | Mining & quarrying | 1964 |
| Amos & Bailey Limited | Professional & scientific | 2004 |
| Amsy Limited | Professional & scientific | 2008 |
| ANA Trading Limited | Professional & scientific | 2008 |
| Anane Ltd | Transport & logistics | 2023 |
| Ananta Healthcare Holdings Limited | Health & social care | 2026 |
| Ananta London Limited | Other services | 2025 |
| Anap Ltd | Administrative & support | 2016 |
| Andrew Quinn Petroleum Engineering Limited | Professional & scientific | 2011 |
| Andrews Recovery Limited | Water & waste | 2000 |
| Andromeda IT Services Limited | Information & communication | 2005 |
| Andscon Limited | Manufacturing | 2006 |
| Andy Curd Productions Ltd | Information & communication | 2016 |
| ANG Medico-Legal Services Ltd | Education | 2004 |
| Angelo Mews Management Limited | Households | 2018 |
| Angels Shelter International CIC | Health & social care | 2026 |
| Anglia Secure Homes (South East) Limited | Construction | 1936 |
| Anglo Aquatic Plant Company Limited | Agriculture & fishing | 1965 |
| Anglo Orient Trading Limited | Wholesale & retail | 1997 |
| Anglo-Arabic Graphics Limited | Information & communication | 1991 |
| Anglo-European Engineers Limited | Professional & scientific | 1991 |
| Anglonorse Furnishings Limited | Wholesale & retail | 2002 |
| Anilrom Limited | | 1978 |
| Anita Impex Limited | Construction | 1993 |
| Annette Limited | Administrative & support | 2021 |
| Annex Limited | Construction | 1986 |
| Annie Deadman Limited | Arts & recreation | 2003 |
| Anpas Limited | Professional & scientific | 2003 |
| Anrk Ltd | Information & communication | 2013 |
| ANS Associates Limited | Professional & scientific | 2003 |
| Anthony Bentley Classics Limited | Real estate | 2007 |
| Anthony Bruton Limited | Arts & recreation | 2013 |
| Anthony Mcnamara | | 1998 |
| Anthus Mews Management Co. Limited | Households | 1984 |
| Antiques and Interior Innovations Ltd | Wholesale & retail | 2007 |
| Anupam Jewellers Ltd. | Wholesale & retail | 1999 |
| Anvil Media Limited | Arts & recreation | 2015 |
| Apex Auto Studios Limited | | 1974 |
| Apex Company Services Ltd | Administrative & support | 1991 |
| Apex Corporate Limited | Extraterritorial | 2006 |
| Apex Tax Services Limited | Professional & scientific | 1997 |
| APK Property & Management Limited | Administrative & support | 1997 |
| Apogee Flow Systems Ltd | Manufacturing | 2000 |
| Apollo Heating Services Limited | Wholesale & retail | 1983 |
| App Effects UK Limited | Arts & recreation | 2013 |
| Apple and Orchid Ltd | Wholesale & retail | 2018 |
| Apple.Com Ltd | Extraterritorial | 2000 |
| Appleacre Investments Limited | Real estate | 1997 |
| Apps DBA Limited | Extraterritorial | 2004 |
| APR Financial Management Limited | Extraterritorial | 2005 |
| AQQ Limited | Real estate | 2002 |
| Aqua Express Cargo Services Ltd | Transport & logistics | 2025 |
| Aqua-Media International Limited | Information & communication | 1993 |
| Aqualite Trading Limited | Wholesale & retail | 1997 |
| ARA Construction Design Ltd | Construction | 2021 |
| Arakis Consultancy Limited | Information & communication | 2000 |
| Aravis Group Ltd | Professional & scientific | 2010 |
| ARC Renovations (Surrey) Limited | Construction | 2007 |
| Archer House Limited | Information & communication | 2006 |
| Archersup Productions Limited | Information & communication | 1999 |