| Armfix Group Ltd | Construction | 2021 |
| ARO Archive Ltd | Arts & recreation | 2018 |
| Aron Accountancy Ltd | Professional & scientific | 2017 |
| Aroris Ltd | Hospitality | 2020 |
| Aroundtheriver Ltd | Wholesale & retail | 2023 |
| Arpx Service Ltd | Other services | 2022 |
| Arrcat Limited | Hospitality | 2021 |
| Arress Ltd | Hospitality | 2023 |
| Arrow Pharmacare Ltd | Wholesale & retail | 2023 |
| ARS SERVICES1 Ltd | Construction | 2026 |
| Arslanboga Limited | Extraterritorial | 2022 |
| Art - Building and Property Management Ltd | Construction | 2021 |
| Art 2 Art Therapy Ltd | Health & social care | 2021 |
| Artecnika Ltd | Information & communication | 2022 |
| Artevista Livings Ltd | Wholesale & retail | 2025 |
| Arthainternational Ltd | Wholesale & retail | 2024 |
| Articulator Limited | Wholesale & retail | 2008 |
| Artifex Ventures Ltd | Information & communication | 2026 |
| Artisan Premium Foods Limited | Manufacturing | 2024 |
| Artius Interiors Limited | Construction | 2013 |
| Artone Holdings II Ltd | Financial services | 2025 |
| Artpress Cards Ltd | Wholesale & retail | 2021 |
| Artpress Holdings Ltd | Financial services | 2021 |
| Artpress Publishing Limited | Manufacturing | 2009 |
| Arul & Sanan Property Ltd | Real estate | 2025 |
| Arul & Sanan PVT Ltd | Wholesale & retail | 2025 |
| Arundel Court Limited | Households | 2018 |
| Arundel Gate Management Company Ltd | Households | 2025 |
| ARY Ltd | Information & communication | 2015 |
| Aryam Consulting Limited | Information & communication | 2016 |
| Aryd Consulting Limited | Professional & scientific | 2016 |
| Asap Chilvers Limited | Real estate | 2023 |
| Asbestos 247 Environmental Ltd | Professional & scientific | 2022 |
| Ascend Global Technology UK Ltd | Wholesale & retail | 2025 |
| Ascendancy Financial Solutions Ltd. | Financial services | 2017 |
| Ascent Design to Print Limited | Manufacturing | 2004 |
| Ascott CAB Co. Ltd | Extraterritorial | 2021 |
| Ascotts Group Limited | Wholesale & retail | 1976 |
| Aseda Shea Ltd | Manufacturing | 2025 |
| ASF Dustless Blasting Limited | Construction | 2023 |
| ASF Real Estates Ltd | Real estate | 2024 |
| ASF Waterproofing Specialists Limited | Other services | 2011 |
| Ashapexlogistic Limited | Transport & logistics | 2026 |
| Ashby COX Design Limited | Professional & scientific | 2023 |
| Ashcroft Physiotherapy Limited | Health & social care | 2024 |
| Ashmere Advisory Ltd | Professional & scientific | 2026 |
| Asho Consulting Limited | Information & communication | 2022 |
| Ashraf & Co Accountants Ltd | Professional & scientific | 2021 |
| Ashta Siddhi Vinayaka Limited | Hospitality | 2024 |
| Ashton Bentley Trading Limited | Manufacturing | 2024 |
| ASK the Impossible Limited | Professional & scientific | 2020 |
| ASL Group London Ltd | Manufacturing | 2023 |
| ASL Lifting Ltd | Manufacturing | 2023 |
| Asmarina Fashion Limited | Manufacturing | 2021 |
| Asmarina Food Limited | Hospitality | 2024 |
| Asmarina One Limited | Arts & recreation | 2017 |
| Asmarina Properties Ltd | Real estate | 2018 |
| Aspen Grove (Bean) Management Limited | Households | 1998 |
| Aspen Services London Limited | Extraterritorial | 2014 |
| Aspire DG Ltd | Real estate | 2021 |
| Aspire European Living Limited | Wholesale & retail | 2017 |
| Aspiring Barristers Ltd | Professional & scientific | 2020 |
| Aspv Consultancy Limited | Financial services | 2008 |
| Aspv Ltd | Real estate | 2026 |
| ASR Investment Services Ltd | Real estate | 2025 |
| Asra Store Limited | Wholesale & retail | 2024 |
| Assembly IT Technology Support Ltd | Financial services | 2016 |
| Assetcorp Ltd | Real estate | 2014 |
| Assets Insights Ltd | Education | 2026 |
| Associated Interim Management Limited | Information & communication | 2000 |
| Associated Lifts Ltd | Professional & scientific | 2018 |
| Assur Capital Partners Limited | Financial services | 2023 |
| Assure Business Associates Ltd | Administrative & support | 2018 |
| Assure Tutoring Ltd | Education | 2026 |
| Assured Quality & Compliance Consultancy Ltd | Professional & scientific | 2017 |
| AST Signature Ltd | Wholesale & retail | 2026 |
| Aston Building Developments Limited | Construction | 2005 |
| Aston Building Services (Kent) Ltd | Construction | 2019 |
| Aston Design & Construction Ltd | Construction | 2019 |
| Astoria Cafe Ltd | Hospitality | 2025 |
| Astra Digital Ltd | Professional & scientific | 2025 |
| Astrosyn Contract Interiors Limited | Construction | 1993 |
| Astwood Homes Limited | Construction | 2014 |
| AT & a Resources Limited | Wholesale & retail | 2014 |
| AT ALL Costs Ltd | Wholesale & retail | 2025 |
| Atafo Ltd | Wholesale & retail | 2021 |
| Atamboq Properties Limited | Real estate | 2022 |
| Atfe Consulting Ltd | Professional & scientific | 2023 |
| Athena Aesthetics & Wellbeing Clinic Ltd | Other services | 2025 |
| Athena Dhir Holdings Ltd | Financial services | 2017 |
| Athena Distribution Limited | | 1992 |
| Athena Management Group Ltd | Wholesale & retail | 2017 |
| Athlone Care Ltd | Administrative & support | 2006 |
| Athlone Healthcare Group Limited | Financial services | 2008 |
| Atlant Living Ltd | Professional & scientific | 2017 |
| Atlantique Hotels (Borough) Limited | Hospitality | 2016 |
| Atlantique Hotels (Farringdon) Limited | Hospitality | 2016 |
| Atlantique Hotels (Management) Limited | Hospitality | 2016 |
| Atman Care Ltd | Health & social care | 2017 |
| Atmosphere Contracts & Design Limited | Manufacturing | 2010 |