| Anne Wayne Property Ltd | Real estate | 2020 |
| Anne Wayne Supported Housing Limited | Real estate | 2025 |
| Anney Ventures Limited | Hospitality | 2011 |
| Anoma Properties Ltd | Real estate | 2025 |
| Anomaly Guitar Limited | Manufacturing | 2018 |
| ANP Ophthalmology Limited | Health & social care | 2023 |
| Anster Developments Ltd | Real estate | 2024 |
| Anster Utilities Ltd | Construction | 2020 |
| Anthony Bourner Roofing Ltd | Construction | 2025 |
| Anthony Britton Construction Limited | Construction | 2009 |
| Anticc Roofing and Building Ltd | Construction | 2022 |
| Antoine Estates Limited | Real estate | 2025 |
| Antra Property Solutions Ltd | Real estate | 2026 |
| Anubis Security Services Ltd | Administrative & support | 2022 |
| Anyanwu Limited | Health & social care | 2012 |
| AOA Diagnostics UK Ltd | Health & social care | 2020 |
| Aocy Aesthetics Ltd | Other services | 2024 |
| AOE Group Ltd | Public administration | 2025 |
| Apcm Services Ltd | Construction | 2021 |
| Apex Car Rental (Norwich) Limited | Administrative & support | 1989 |
| Apex Prestige Car Hire Ltd | Administrative & support | 2024 |
| Apexx Carpentry Ltd | Construction | 2023 |
| Aphp Limited | Other services | 2001 |
| APK Consulting Ltd | Construction | 2023 |
| APM Rentals Ltd | Households | 2024 |
| Apollo Elite Properties Limited | Real estate | 2024 |
| App Scaffolding Limited | Construction | 2016 |
| Apparatus Holdings Limited | Professional & scientific | 2023 |
| Apparatus Software Limited | Professional & scientific | 2019 |
| Appleby & Wood (London) Ltd | Professional & scientific | 2020 |
| Applegate Estates Limited | Administrative & support | 2001 |
| Applied Environmental Solutions Ltd | Professional & scientific | 2002 |
| Appointee Services Ltd | Professional & scientific | 2018 |
| Approach Research Centre Ltd. | Information & communication | 2017 |
| Apricus Estates Limited | Real estate | 2023 |
| Aqua Q Ltd. | Construction | 2018 |
| Aquachain Limited | Professional & scientific | 2003 |
| Aquaflow Utilities Ltd | Construction | 2025 |
| Aqualogy Ltd | Agriculture & fishing | 2009 |
| Aquinas College Akure Old Students’ Association (Acaosa) Europe and the United Kingdom (UK) CIC | Education | 2026 |
| AR Fire Ltd | Professional & scientific | 2019 |
| AR Hygiene and Therapy Services Limited | Health & social care | 2016 |
| Araliya Solutions Ltd | Professional & scientific | 2011 |
| Aramedu Ltd | Wholesale & retail | 2024 |
| Arbor Lane Interiors Ltd | Construction | 2010 |
| Arbour Wood Ltd | Manufacturing | 2007 |
| ARC Acquisitions Limited | Administrative & support | 2006 |
| ARC Commercial Limited | Administrative & support | 2008 |
| ARC Couriers Limited | Other services | 2015 |
| ARC Estates (Hartley) Limited | Administrative & support | 2008 |
| ARC Infinity UK Limited | Agriculture & fishing | 2025 |
| Arc-Cs Ltd | Professional & scientific | 2002 |
| Arca Property Investments Ltd | Real estate | 2025 |
| Arcade Care Limited | Professional & scientific | 2016 |
| Arcarius Complete Property Services Limited | Construction | 2023 |
| Arcelormittal Kent Wire Limited | Manufacturing | 1987 |
| Arch Cosmetics Ltd | Other services | 2024 |
| Arch Mason Property Ltd | Real estate | 2024 |
| Arch South East Ltd | Construction | 2025 |
| Archerius Healthcare Limited | Health & social care | 2024 |
| Archers Motors Ltd | Wholesale & retail | 2023 |
| Arches Local CIC | Other services | 2022 |
| Architecting Secure Systems for the Internet Enterprise (Assie) Ltd | Information & communication | 2020 |
| Architecture & Urban Design Bureau Limited | Professional & scientific | 2008 |
| Architecture Design Limited | Professional & scientific | 2013 |
| Architype Metalwork Limited | Administrative & support | 2013 |
| Arden & Arden Ltd | Real estate | 2022 |
| Ardent Ace Consulting Ltd | Information & communication | 2022 |
| Areka Lodge Ltd | Real estate | 2023 |
| Ariiis Ltd | Real estate | 2025 |
| Ariston Cleaners Ltd | Administrative & support | 2020 |
| Ariston London Limited | Administrative & support | 2022 |
| Ariyo Consulting Limited | Professional & scientific | 2024 |
| Arizmi Labs Ltd | Information & communication | 2026 |
| ARK Beds Ltd | Manufacturing | 2026 |
| ARK NPT Limited | Wholesale & retail | 2022 |
| Arkshot Ltd | Information & communication | 2023 |
| Arlunio Limited | Professional & scientific | 2021 |
| Arm-G Ltd | Real estate | 2023 |
| Armage Ltd | Extraterritorial | 2026 |
| Armands-G Ltd | Transport & logistics | 2019 |
| Armiva Ltd | Real estate | 2025 |
| Armour Security Systems Limited | Construction | 2006 |
| Arne Properties Ltd | Administrative & support | 2023 |
| Aros Kent Barbers Ltd | Other services | 2021 |
| Arsh Transport Ltd | Other services | 2013 |
| Art Build & Design Ltd | Construction | 2017 |
| Art Construction Training and Assessments Ltd | Education | 2017 |
| Art Plant Hire Ltd | Administrative & support | 2025 |
| Artan Auto Services Limited | Wholesale & retail | 2024 |
| Artemis Intelligence Ltd | Information & communication | 2008 |
| Artesian Plumbing&Heatings Ltd | Construction | 2024 |
| Artscout Ltd | Information & communication | 2025 |
| Aruvy Limited | Wholesale & retail | 2023 |
| Arvel Group Ltd | Wholesale & retail | 2025 |
| Arww Consulting Ltd | Information & communication | 2017 |
| Arxfina Capital Ltd | Real estate | 2025 |
| Arya and Anya Ltd | Information & communication | 2024 |
| ARYAN2 Ltd | Health & social care | 2010 |
| Aryus Ltd | Wholesale & retail | 2025 |