| Asher Solutions Ltd | Construction | 2021 |
| Ashn Research Limited | Professional & scientific | 2026 |
| Ashrim UK Ltd | Real estate | 2022 |
| Ashtavinayak Developments Ltd | Real estate | 2024 |
| Ashton Riley Practices Ltd | Wholesale & retail | 2026 |
| Asia Estates Limited | Administrative & support | 2007 |
| Asia T.V. Limited | Information & communication | 1992 |
| Asians in Business Limited | Professional & scientific | 2015 |
| ASK Catering Limited | Hospitality | 2025 |
| ASK Dent Ltd | Health & social care | 2012 |
| ASL Partners Ltd | Professional & scientific | 2007 |
| Asli 2 Limited | Information & communication | 2011 |
| Aslon Limited | Real estate | 2011 |
| ASM Company Secretaries Limited | Extraterritorial | 2002 |
| ASO Developments Limited | Wholesale & retail | 2005 |
| Aspect Ratio TV Limited | Other services | 2014 |
| Aspire Academy London Ltd | Education | 2025 |
| Aspire Fundraising Limited | Other services | 1989 |
| Aspire Trading 2014 Ltd | Professional & scientific | 2014 |
| Aspire Trading 2020 Limited | Financial services | 2020 |
| Aspire Wellbeing Centre Community Interest Company | Health & social care | 2012 |
| Asquith Renew Ltd | Water & waste | 2007 |
| Asra Properties Limited | Real estate | 2011 |
| Assent Capital Management Limited | Real estate | 2010 |
| Associate Halal Foods Ltd | Wholesale & retail | 2020 |
| Associated Group of Companies (UK) Ltd | Professional & scientific | 2015 |
| Association for Spinal Injury Research Rehabilitation and Reintegration | Health & social care | 1999 |
| Association of Ghanaian Ex-Servicemen & Women UK Ltd | Other services | 2004 |
| AST DRY Lining Ltd | Construction | 2018 |
| AST Law Limited | Professional & scientific | 2022 |
| Asta Accountants Ltd | Professional & scientific | 2020 |
| Aston James Limited | Real estate | 2021 |
| Aston Leach Creative Ltd | Professional & scientific | 2025 |
| Aston Property Limited | Real estate | 1998 |
| Aston Stanley Ltd | Real estate | 2026 |
| Astral Thompson Metalworks Ltd | Manufacturing | 2022 |
| Aswad Ltd | Wholesale & retail | 2018 |
| Aswaduk Limited | Construction | 2018 |
| Aswin Ltd | Information & communication | 2017 |
| AT Your Service Cleaning Contractors Limited | Administrative & support | 2008 |
| Ataka Consultants Limited | Administrative & support | 1999 |
| ATB Top Finishes Ltd | Construction | 2020 |
| Atelier Haus Ltd | Real estate | 2019 |
| Atelier Luxury Group UK Ltd | Wholesale & retail | 2023 |
| Athenaeum Freehold Limited | Real estate | 2022 |
| Athlaitic Ltd | Information & communication | 2025 |
| ATI - Systems Limited | Information & communication | 2007 |
| Atlante Import Italy Ltd | Other services | 2017 |
| Atlantic Mews (Management) Limited | Households | 2001 |
| Atlas Property Finance Limited | Financial services | 2020 |
| Atlas Vehicle Hire Limited | Transport & logistics | 2013 |
| Atlas Wharf Properties Ltd | Real estate | 2018 |
| Atmiya Properties Ltd | Real estate | 2022 |
| Atnight Limited | Professional & scientific | 2019 |
| Atomiq Ltd | Professional & scientific | 2024 |
| Atomism Limited | Professional & scientific | 2002 |
| Atraco Ltd | Administrative & support | 2009 |
| Atticus West Limited | Administrative & support | 2015 |
| Attract Super Confidence Ltd | Information & communication | 2022 |
| Attribute 360 Ltd | Professional & scientific | 2022 |
| Atwi Holdings Limited | Wholesale & retail | 2024 |
| Atwi Retail Services Limited | Wholesale & retail | 2026 |
| ATWOOD123 Limited | Financial services | 2014 |
| ATZ Logistics Ltd | Transport & logistics | 2019 |
| Audit Network Limited | Professional & scientific | 2009 |
| August Estates Limited | Real estate | 2007 |
| AUM 432 Limited | Real estate | 2024 |
| AUM Hub Ltd | Real estate | 2025 |
| AUM Real Estate Limited | Real estate | 2022 |
| Aumonier Ltd | Hospitality | 2020 |
| Aura Kitchen Ltd | Wholesale & retail | 2025 |
| Aura(Bushey) Limited | Hospitality | 2015 |
| Aureeba Lettings Limited | Real estate | 2025 |
| Aurel Plastering Ltd | Construction | 2018 |
| Aurex Global Payments Limited | Financial services | 2025 |
| Aurora Box London Limited | Wholesale & retail | 2025 |
| Austin Commercial Limited | Real estate | 2021 |
| Authentic Ayurveda Limited | Wholesale & retail | 2005 |
| Auto & Storage Ltd | Wholesale & retail | 2026 |
| Auto Bloom Ltd | Wholesale & retail | 2026 |
| Auto Change UK Ltd | Construction | 2020 |
| Auto Hub Premium Limited | Wholesale & retail | 2019 |
| Auto Motto Limited | Administrative & support | 2022 |
| Auto Xpress ( UK ) Limited | Wholesale & retail | 2009 |
| Autobarn Automotive Ltd | Wholesale & retail | 2011 |
| Autobot Motor Centre Ltd | Wholesale & retail | 2012 |
| Automate Lead Ltd | Information & communication | 2023 |
| Automotion Technologies Limited | Administrative & support | 2005 |
| Autoto Ltd | Construction | 2018 |
| AV LDN Ltd | Administrative & support | 2024 |
| AV Surge-On Ltd | Administrative & support | 2019 |
| AVA K Events Ltd | Wholesale & retail | 2019 |
| Avalloumi Limited | Real estate | 2017 |
| Avantgarde Consultancy Ltd | Wholesale & retail | 2010 |
| Avanti Fostering Ltd | Health & social care | 2019 |
| Avanti Schools Trust | Education | 2011 |
| Avanti Services Ltd | Administrative & support | 2017 |
| Avantum Limited | Professional & scientific | 1997 |
| AVARIS24 Limited | Construction | 2025 |
| Avdian Ltd | Information & communication | 2022 |