| Akeman Mews Management Company Limited | Households | 2016 |
| AL Nahyan Holdings Limited | Real estate | 2015 |
| Albert (London) Development Ltd | Real estate | 2022 |
| Alchemy Interactive Limited | Manufacturing | 1998 |
| Alderbrook (Heathfield Road) Management Company Limited | Households | 2023 |
| Alderhurst Englefield Green MAN Co Ltd | Households | 2024 |
| Aldgate Developments Limited | Administrative & support | 2011 |
| Alexander Consultancy Services Limited | Information & communication | 2015 |
| Alfriston Leisure Ltd | Education | 2014 |
| Alfriston School | Education | 2012 |
| Alice Garages Limited | Real estate | 2002 |
| Alida Penn Investments Limited | Real estate | 1971 |
| Alington Consulting Limited | Professional & scientific | 2022 |
| Alison Hood Consulting Ltd | Professional & scientific | 2018 |
| Alkalisha Limited | Real estate | 2015 |
| ALL Pet Solutions Limited | Wholesale & retail | 2006 |
| ALL Pond Solutions Limited | Wholesale & retail | 2011 |
| ALL4DRINKS Ltd | Wholesale & retail | 2023 |
| Alley KAT Trading Company Ltd | Wholesale & retail | 2024 |
| Allthingscommon Limited | Professional & scientific | 2025 |
| Alluvia Health Limited | Health & social care | 2023 |
| Almago Limited | Wholesale & retail | 2018 |
| Alpha Bravo Consulting Ltd | Education | 2025 |
| Alpha Square Ltd | Information & communication | 2010 |
| Alphabet Street Property Ltd | Real estate | 2022 |
| Alphabook Group Limited | Information & communication | 2017 |
| Alternative Packaging Limited | Wholesale & retail | 1984 |
| Altersapiens Limited | Information & communication | 2023 |
| Altura Learning United Kingdom Limited | Public administration | 2008 |
| Amanti Emeralds Ltd | Wholesale & retail | 2025 |
| Ambra Group Limited | Administrative & support | 2025 |
| Amersham Corporate Services Limited | Administrative & support | 1993 |
| AMF Profit Group Ltd | Administrative & support | 2023 |
| AMF Property Lettings Ltd | Real estate | 2023 |
| AMH Advisory Limited | Administrative & support | 2024 |
| Amis Trading Limited | Wholesale & retail | 2010 |
| Amkd Ltd | Health & social care | 2024 |
| Amplifico Solutions Limited | Professional & scientific | 2019 |
| ANA Careers Ltd | Information & communication | 2026 |
| Andelin Limited | Real estate | 2003 |
| Anderson Consultants Ltd | Information & communication | 2003 |
| Anderson IT Limited | Information & communication | 2001 |
| Anderson, Brown & Clarke Limited | Real estate | 2016 |
| Andrew Carr Associates Limited | Professional & scientific | 2008 |
| Andrew Louca Lighting Limited | Information & communication | 2010 |
| Aneek Homes Limited | Real estate | 2025 |
| Anfield Investments Limited | Administrative & support | 1995 |
| Angelheart Care Ltd | Health & social care | 2019 |
| Anglo Industrial Holdings Ltd | Manufacturing | 2010 |
| Anique Interiors Limited | Construction | 2022 |
| Anjica Limited | Wholesale & retail | 2025 |
| Anoxal Limited | Real estate | 2019 |
| Ansarada UK Limited | Administrative & support | 2008 |
| Anthony Fieldhouse & Co Ltd | Construction | 2018 |
| Antiques ARE Green Limited | Extraterritorial | 2009 |
| Antoniou Group Limited | Manufacturing | 2018 |
| AO3 Holdings Limited | Financial services | 2017 |
| AO3 Investments Limited | Real estate | 2017 |
| AP Photographic Centre Limited | Wholesale & retail | 2012 |
| Apache Limited | Administrative & support | 2021 |
| Apex Business Management (UK) Limited | Professional & scientific | 2009 |
| Apex Estates Limited | Real estate | 2018 |
| APJ Webb Limited | Professional & scientific | 2017 |
| APM Vehicle Hire & Purchase Ltd | Administrative & support | 2023 |
| Applicant Mortgage Brokers Limited | Financial services | 2020 |
| APQ Group Developments Ltd | Construction | 2020 |
| APQ Group Limited | Construction | 2019 |
| APS Window Company (Bucks) Limited | Construction | 2014 |
| APT House Constructions Limited | Construction | 2026 |
| APT House Holdings Limited | Financial services | 2025 |
| APT House Limited | Real estate | 2020 |
| APW Insights Limited | Professional & scientific | 2023 |
| Aquagem Marine Innovations Limited | Transport & logistics | 2024 |
| Aquarius Acquisitions Ltd | Real estate | 2025 |
| Aquinna Homes PLC | Construction | 2005 |
| ARA Fitness Limited | Wholesale & retail | 2016 |
| Aracari Group Ltd | Real estate | 2023 |
| ARC Advisors Ltd | Professional & scientific | 2025 |
| ARC Three Collective Ltd | Professional & scientific | 2026 |
| Arch Stanton Productions Ltd | Professional & scientific | 2012 |
| Arckle Investments Limited | Professional & scientific | 1990 |
| Arelleon Ltd | Hospitality | 2026 |
| Argent Business Services Limited | Administrative & support | 2017 |
| Aria MEP Limited | Real estate | 2020 |
| Arithmic Financial Consultancy Ltd | Professional & scientific | 2014 |
| ARK Integrations Limited | Information & communication | 2011 |
| ARK Resources Limited | Mining & quarrying | 2016 |
| Arkp Investments Ltd | Real estate | 2020 |
| Arlion Ltd | Other services | 2023 |
| Arnold Funeral Service Limited | Other services | 1993 |
| ARP Holding Limited | Professional & scientific | 2012 |
| Arrowmark International Limited | Financial services | 2019 |
| Art Living Ltd | Real estate | 2017 |
| Art Real Estate Ltd | Real estate | 2020 |
| Artdpt. Limited | Professional & scientific | 2021 |
| Arthur's Partners LLP | | 2016 |
| Artia Accountancy Limited | Real estate | 2017 |
| Artis UK Limited | Extraterritorial | 2016 |
| Artisan Armours Limited | Arts & recreation | 2005 |
| Artnest Studios Limited | Arts & recreation | 2014 |