| ANT UK Trading Ltd | Transport & logistics | 2024 |
| Anthony O'Keefe Souvenirs Limited | Wholesale & retail | 2017 |
| Anton London Limited | Wholesale & retail | 2014 |
| Anxiety Care UK Ltd | Health & social care | 2011 |
| Anya Developments Limited | Real estate | 2004 |
| ANZ Trading Limited | Wholesale & retail | 2013 |
| Aofbc Skills & Education Ltd | Education | 2018 |
| AOK Minibuses Ltd | Transport & logistics | 2017 |
| AOV Installations & Servicing Ltd | Construction | 2021 |
| AOW Group Ltd | Construction | 2022 |
| AP Vehicle Cosmetics Limited | Wholesale & retail | 2014 |
| APC Catering Ltd | Hospitality | 2025 |
| Apex (Hinckley) Limited | Professional & scientific | 2006 |
| Apex (Loughborough) Limited | Professional & scientific | 2004 |
| Apex Document Solutions Group Ltd | Administrative & support | 2017 |
| Apex Fine Finish Ltd | Construction | 2026 |
| Apex Steel Holdings Limited | Construction | 2002 |
| Apex Steel Structures Limited | Construction | 1995 |
| Apian House Properties Limited | Real estate | 2021 |
| Apollo Bookmakers Limited | Arts & recreation | 2010 |
| Apollo Property Investment Limited | Construction | 2012 |
| Apostle Security Limited | Administrative & support | 2025 |
| Apparel Manufacturing Technology & Marketing Solutions UK Limited | Manufacturing | 2012 |
| Appdelegate Ltd | Information & communication | 2015 |
| Appsolve Group Limited | Information & communication | 2026 |
| Apptech Dynamics Limited | Information & communication | 2025 |
| APR Boilers Ltd | Construction | 2023 |
| Apsley Galliard Connect Limited | Administrative & support | 2022 |
| Aqarey Ltd | Real estate | 2023 |
| AQM Group Limited | Hospitality | 2017 |
| Aqua Residential Care Ltd | Health & social care | 2019 |
| Aquaflame Plumbing Services Limited | Construction | 2016 |
| Aquastat Environmental Services Limited | Professional & scientific | 2011 |
| AR Astwood Ltd | Real estate | 2021 |
| AR Bancroft Ltd | Real estate | 2021 |
| AR City Ltd | Real estate | 2020 |
| AR Varden 5 Ltd | Real estate | 2024 |
| AR Varden Ltd | Real estate | 2022 |
| AR Watson Ltd | Construction | 2018 |
| ARA Homes Group Limited | Financial services | 2022 |
| ARA Homes Limited | Construction | 2002 |
| ARA Traders Limited | Wholesale & retail | 2019 |
| Arankavalan Property Ltd | Real estate | 2023 |
| ARC Construction (Essex) Limited | Construction | 2018 |
| ARC Total Management Limited | Professional & scientific | 2017 |
| Arch Ceiling Limited | Professional & scientific | 2016 |
| Archietof Limited | Administrative & support | 2017 |
| Archway Health Care Limited | Health & social care | 2010 |
| Arcicris Ltd | Construction | 2020 |
| Arcs Holdings Ltd | Real estate | 2020 |
| Arctura Tech Ltd | Information & communication | 2025 |
| Arena Hairstylists Limited | Other services | 1997 |
| Ares Health Limited | Wholesale & retail | 2023 |
| Areto Ltd | Professional & scientific | 2024 |
| Argentalia Ltd | Hospitality | 2020 |
| Ariana Global Limited | Extraterritorial | 2005 |
| Arietis Estates LLP | | 2024 |
| ARJ Investments (London) Limited | Real estate | 2022 |
| ARK Build (Holdings) Ltd | Construction | 2019 |
| ARK Build PLC | Construction | 1999 |
| ARK FMS PLC | Construction | 2021 |
| ARK MEP PLC | Construction | 2013 |
| Arlil Project Development Limited | Professional & scientific | 2017 |
| ARM Estate Properties Limited | Real estate | 2025 |
| Arnhem Search Ltd | Professional & scientific | 2017 |
| Arnies Scaffolding Ltd | Construction | 2020 |
| Arnios Ltd | Information & communication | 2023 |
| Arnvale Developments Limited | Construction | 2020 |
| Art Class Chigwell, Loughton, Buckhurst Hill Ltd | Hospitality | 2026 |
| Art Contractors Ltd | Construction | 2011 |
| Arthurs Adventures Ltd | Wholesale & retail | 2024 |
| Artichoke Homes Limited | Real estate | 2016 |
| Artificial Intelligence Services Limited | Information & communication | 2023 |
| Artillery House RTM Company Ltd | Households | 2016 |
| Asbestos Analysts Limited | Professional & scientific | 2017 |
| Asbestos Training Limited | Professional & scientific | 2010 |
| Asea Beauty Limited | Other services | 2025 |
| ASG Lighting Solutions Limited | Construction | 2020 |
| Asgard Heritage Ltd | Construction | 2025 |
| Asgard Home Improvements Limited | Construction | 2014 |
| Asgard Property Management Ltd | Real estate | 2024 |
| ASH Court (South Woodford) Residents Association Limited | Households | 1961 |
| ASH Cummings Holdings Ltd | Construction | 2021 |
| ASH Cummings Properties Limited | Real estate | 2018 |
| Ashburn Homes Ltd | Real estate | 2021 |
| Ashburn Residential Ltd | Administrative & support | 2021 |
| Ashwells Estates Limited | Real estate | 2020 |
| Asian Bridal Fest UK Ltd | Information & communication | 2026 |
| ASM Property & Development Ltd | Real estate | 2023 |
| Asmaas Chasmaas Ltd | Health & social care | 2019 |
| ASPIRE2RETIRE Financial Solutions Limited | Professional & scientific | 2023 |
| Asra Cutler Property Limited | Real estate | 2026 |
| Asset Enhancement Limited | Professional & scientific | 2025 |
| Assetfresh Property Ltd | Real estate | 2020 |
| Assl Properties Limited | Real estate | 2002 |
| Associated Fire Systems Limited | Construction | 2005 |
| Associated Glass Limited | Construction | 2000 |
| Assura Wealth Management Limited | Professional & scientific | 2017 |
| Astobic Ltd | Wholesale & retail | 2025 |
| Aston Court Estates Limited | Households | 1990 |