| Antoine West Associates Limited | Professional & scientific | 2009 |
| Antonios Hair Studio Ltd | Other services | 2026 |
| Anulytics Limited | Professional & scientific | 2025 |
| AP14 Ltd | Administrative & support | 2017 |
| Apel Chemicals UK Limited | Wholesale & retail | 2017 |
| Apex Foods & Catering Limited | Hospitality | 2024 |
| Apex Protection and Security Services Ltd | Administrative & support | 2018 |
| Apex Roofing London Ltd | Construction | 2023 |
| Apexguard Roofers Limited | Construction | 2026 |
| Apni Company Limited | Wholesale & retail | 2019 |
| Apostol Limited | Professional & scientific | 2025 |
| App & Go Ltd | Transport & logistics | 2024 |
| Applied Partners Limited | Professional & scientific | 2026 |
| Applied Radio Engineering Limited | Information & communication | 2015 |
| Approved Building Solutions Limited | Construction | 2020 |
| Aptidrive Limited | Health & social care | 2018 |
| Aquacaptech Ltd | Manufacturing | 2025 |
| Aquarius Consultancies Ltd | Professional & scientific | 2023 |
| Aquarius Energy Consulting Ltd | Administrative & support | 2010 |
| AR Tech Advisory Ltd | Administrative & support | 2023 |
| Arateus Healthcare Ltd | Health & social care | 2022 |
| ARC Bespoke Ltd | Manufacturing | 2023 |
| ARC Inc Limited | Information & communication | 2016 |
| ARC Investment Group Limited | Financial services | 2024 |
| Arcade Sports Group Limited | Information & communication | 2024 |
| Arch Health & Fitness Ltd | Arts & recreation | 2025 |
| Archgenerate Limited | Construction | 2025 |
| Architology Architecture & Design Ltd | Professional & scientific | 2022 |
| Archive Miriam Ltd | Information & communication | 2010 |
| Archway Concepts Limited | Hospitality | 2022 |
| Arcoda Limited | Construction | 2002 |
| Argentee Associates Limited | Real estate | 2015 |
| Argeron Medical Ltd | Wholesale & retail | 2023 |
| Argon Financial Services Limited | Financial services | 2018 |
| Aries RAM Cosmeceuticals Limited | Manufacturing | 2022 |
| ARK Modern Properties Ltd | Real estate | 2022 |
| Arlington House (Twickenham) Residents Association Limited | Households | 1991 |
| Army of One Limited | Information & communication | 2023 |
| Arnc Estates Ltd | Real estate | 2026 |
| Arnc Properties Ltd | Real estate | 2024 |
| Arnc Realty Ltd | Real estate | 2025 |
| Arora Convenience Store Ltd | Wholesale & retail | 2024 |
| Arora Property Group Ltd | Real estate | 2025 |
| Around the Post Ltd | Arts & recreation | 2024 |
| Art Vector Limited | Wholesale & retail | 2019 |
| Artillex Ltd | Wholesale & retail | 2023 |
| Artilo AI Ltd | Information & communication | 2023 |
| Arts Consulting Ltd | Information & communication | 2015 |
| Arveen Limited | Wholesale & retail | 2011 |
| AS Properties 1 Limited | Real estate | 2024 |
| AS Properties 2 Limited | Real estate | 2025 |
| Asad Corporation Limited | Wholesale & retail | 2026 |
| Asan Enterprise UK Ltd | Manufacturing | 2024 |
| Asbo Media Ltd | Information & communication | 2020 |
| Ascendant Communications Consultancy Limited | Other services | 2003 |
| Ascension Catholic Academy Trust | Education | 2022 |
| Ascherbrook Limited | Wholesale & retail | 2011 |
| Aseel Medical Ltd | Health & social care | 2015 |
| Asheridge Contracts Ltd | Construction | 2022 |
| Ashington Advisory (Europe) Limited | Professional & scientific | 2015 |
| Ashley Aluminium Limited | | 1968 |
| Ashley Insight Ltd | Professional & scientific | 2011 |
| Ashnyn Ventures Ltd | Information & communication | 2025 |
| Ashton Walker Limited | Professional & scientific | 1988 |
| Asian Music Publishing Ltd | Information & communication | 2011 |
| Asiatique Restaurant Company Limited | Hospitality | 2016 |
| ASK Jeej Limited | Administrative & support | 2012 |
| ASM Future Ltd | Real estate | 2023 |
| ASO Services Ltd | Other services | 2009 |
| Asparagus Enterprises Limited | Information & communication | 2020 |
| Asra PO Ltd | Wholesale & retail | 2026 |
| Association of Independent Movers | Other services | 2013 |
| Aston Viking Limited | Administrative & support | 2010 |
| Astrid Interior Design Ltd | Construction | 2016 |
| Astrospace Limited | Information & communication | 2005 |
| AT IT Consulting Ltd | Information & communication | 2018 |
| Athlixir Ltd | Wholesale & retail | 2024 |
| ATL ROL Limited | Administrative & support | 2023 |
| Atlas Construction Service Ltd. | Professional & scientific | 2008 |
| ATR Refrigeration & Air Conditioning Ltd | Construction | 2024 |
| ATT Sales Limited | Professional & scientific | 2024 |
| Attache Accessories Ltd | Manufacturing | 2026 |
| Attelia Ltd | Wholesale & retail | 2019 |
| Attico Construction Limited | Construction | 2023 |
| Auag Holdings Ltd | Financial services | 2021 |
| Audit Consultancy Services Ltd | Professional & scientific | 2024 |
| Augalupe International Ltd | Professional & scientific | 2017 |
| Auluck Consultancy Limited | Professional & scientific | 2016 |
| AUM Geetha Services Limited | Information & communication | 2012 |
| Auralis Collective Ltd | Wholesale & retail | 2025 |
| Aureliean Ltd | Manufacturing | 2018 |
| Aurigo Hero LP | | 2007 |
| Aurigo Hero New LP | | 2009 |
| Aurigo Hero Promote LP | | 2007 |
| Aurum Health Ltd | Financial services | 2023 |
| Aurum.Ldn Jewellery & Piercings Ltd | Other services | 2023 |
| Authentic African Designs Ltd | Wholesale & retail | 2020 |
| Authority Homes Limited | Real estate | 2016 |
| Autocuehire Limited | Administrative & support | 2025 |
| Automation Outcomes Ltd | Professional & scientific | 2020 |