| Aquasanta Limited | Professional & scientific | 2019 |
| ARA Investments Ltd | Real estate | 2017 |
| Arcas & Construction UK Ltd | Construction | 2022 |
| Archer Signs Limited | Administrative & support | 1998 |
| Archie & Nuno Ltd | Hospitality | 2022 |
| Arclend Group Limited | Wholesale & retail | 2024 |
| Ardour Noble Limited | Professional & scientific | 2003 |
| Ardrea (West London) Limited | Real estate | 2024 |
| Ardrea Property Investments Limited | Real estate | 2020 |
| Aref Imaging Limited | Real estate | 2006 |
| Arek T Ltd | Administrative & support | 2016 |
| Areventsuk Limited | Administrative & support | 2025 |
| Argylle Electronic Systems Ltd | Manufacturing | 2024 |
| Argylle Group Holdings Ltd | Administrative & support | 2018 |
| Argylle Group Ltd | Public administration | 2025 |
| Aries Infra Cloud Limited | Professional & scientific | 2024 |
| Aris Management Services Limited | Real estate | 2023 |
| Ariss Limited | Financial services | 2008 |
| Aristara Limited | Wholesale & retail | 2024 |
| Arjun Investments (London) Limited | Real estate | 2004 |
| ARK Allies Ltd | Professional & scientific | 2016 |
| ARK Allies Properties Ltd | Real estate | 2025 |
| ARK Cloud Solutions Limited | Information & communication | 2024 |
| ARK Green Limited | Administrative & support | 2023 |
| Arkis Communications Ltd | Professional & scientific | 2025 |
| Arlie Bass Limited | Hospitality | 2019 |
| Arlo Electrical Ltd | Construction | 2023 |
| Armaan Randhawa Limited | Transport & logistics | 2020 |
| Armada Pharmacies Limited | Wholesale & retail | 2001 |
| Aroma Lounge 1966 Limited | Hospitality | 2026 |
| Arontone Limited | Financial services | 1978 |
| Arquerial 20TH Century Ltd | Wholesale & retail | 2017 |
| Arraigo Coffee UK Ltd | Wholesale & retail | 2024 |
| Arrow Fitness Ltd | Other services | 2024 |
| Art Carpentry Couk Ltd | Manufacturing | 2019 |
| Art House Imex London Ltd | Construction | 2024 |
| Art Plumbing Limited | Construction | 2022 |
| Art Vivid Ltd | Manufacturing | 2013 |
| Art-Vei Consulting Limited | Information & communication | 2014 |
| Artes Vitae Centre Ltd | Education | 2019 |
| Artisanal Plaster Co. Ltd | Construction | 2025 |
| Artisanale London Ltd | Wholesale & retail | 2020 |
| Arwin Foods Limited | Wholesale & retail | 2011 |
| AS Lodging Ltd | Real estate | 2022 |
| AS Propco Ltd | Real estate | 2026 |
| Asap IT Consulting Limited | Information & communication | 2018 |
| Asar Wealth Management Limited | Financial services | 2016 |
| ASB Medica Limited | Health & social care | 2013 |
| Ascend Contractors Ltd | Construction | 2020 |
| Ascend Move Ltd | Real estate | 2015 |
| Asdatasolutions Ltd | Information & communication | 2025 |
| Ashar Larder Services Ltd | Hospitality | 2024 |
| Ashar Services Limited | Hospitality | 2022 |
| Ashar Tara Larder Services Limited | Hospitality | 2025 |
| Ashar Tara Services Limited | Hospitality | 2022 |
| Ashburn Carpets Ltd | Wholesale & retail | 2011 |
| Ashby House Estate Management Company Ltd | Households | 2021 |
| Ashfordphysiotherapy@Finchley Limited | Health & social care | 2025 |
| Ashiokai Arcade CIC | Manufacturing | 2024 |
| Ashiokai Ltd | Information & communication | 2021 |
| Ashley Drive Residents Association (Osterley) Limited | Real estate | 1992 |
| Ashnilay Ltd | Health & social care | 2015 |
| Ashram Financial Limited | Professional & scientific | 2020 |
| Asinger Community Interest Company | Information & communication | 2013 |
| ASJ Marketplace Ltd | Professional & scientific | 2024 |
| Askari Surgery Ltd | Health & social care | 2025 |
| Aslihan&Co Ltd | Wholesale & retail | 2021 |
| ASN Food and Wine Ltd | Wholesale & retail | 2023 |
| Aspen Medical People Limited | Extraterritorial | 2004 |
| Aspen Medical UK Limited | Health & social care | 2010 |
| Aspire Infotech Limited | Information & communication | 2015 |
| Aspire Overseas Educational Services Limited | Education | 2023 |
| ASR Collectibles Ltd | Wholesale & retail | 2026 |
| Astoria Group Limited | Construction | 2025 |
| Astra MCR Limited | Wholesale & retail | 2016 |
| Astral Projections Lighting Ltd | Arts & recreation | 2019 |
| Astralis HR Solutions Limited | Administrative & support | 2020 |
| Astro Tiger Ltd | Information & communication | 2009 |
| ATH Furniture Ltd | Manufacturing | 2020 |
| Athena Analytics Limited | Wholesale & retail | 2020 |
| Athena Discovery Labs Limited | Information & communication | 2024 |
| ATL Construction Ltd | Construction | 2026 |
| Atlas Accountants Ltd | Professional & scientific | 2018 |
| Atlas GAS Ltd | Construction | 2021 |
| Atlas Gate Ltd | Professional & scientific | 2024 |
| ATM Hospitality Limited | Hospitality | 2025 |
| ATP MED Limited | Health & social care | 2026 |
| Attire Affair UK Private Limited | Wholesale & retail | 2017 |
| Audiovisual and Data Communications Limited | Administrative & support | 2006 |
| Augmenta Solutions Limited | Administrative & support | 2023 |
| Auguste Properties Limited | Real estate | 2024 |
| Aura Clinic London Limited | Health & social care | 2019 |
| Aurora Northern Limited | Real estate | 2021 |
| Aurora South Limited | Professional & scientific | 2023 |
| Authentic Warriors Ethos Ltd | Wholesale & retail | 2021 |
| Auto Lock Professionals Ltd | Wholesale & retail | 2022 |
| Automation & Integration Management Ltd | Transport & logistics | 2021 |
| Avas Properties Limited | Real estate | 2023 |
| Avoca Refurbishments Limited | Construction | 2015 |
| Avtar Mobiles Limited | Wholesale & retail | 2024 |