| AR Building Group Ltd | Construction | 2025 |
| AR Greater London Ltd | Construction | 2024 |
| AR Homes Ltd | Real estate | 2019 |
| AR Integrated Consulting Ltd | Professional & scientific | 2026 |
| AR Investments Co NO1 Ltd | Hospitality | 2019 |
| AR Mechanical Engineering Ltd | Construction | 2026 |
| AR Mortgage Services Limited | Financial services | 2015 |
| AR Topnotch Limited | Real estate | 2022 |
| ARA Lanka Limited | Wholesale & retail | 2025 |
| ARA Lanka Meat House Limited | Wholesale & retail | 2026 |
| ARA Smiles Ltd | Health & social care | 2024 |
| Arabian Garments Ltd | Wholesale & retail | 2025 |
| Arable Glen Ltd | Real estate | 2024 |
| Arafat Ltd | Wholesale & retail | 2013 |
| Aragon Property Consultancy Limited | Professional & scientific | 2020 |
| Aramystic Ltd | Wholesale & retail | 2024 |
| Aran Lodge Limited | Real estate | 2004 |
| Arao Consultancy Ltd | Information & communication | 2015 |
| Aratus Building Services Ltd | Construction | 2021 |
| ARB Partners Ltd | Professional & scientific | 2024 |
| Arba Consultancy Services Ltd | Professional & scientific | 2012 |
| Arbalest Technologies Ltd | Information & communication | 2025 |
| Arbequina UK Limited | Wholesale & retail | 2019 |
| Arbre Watches Limited | Manufacturing | 2018 |
| ARC EAR Care Ltd | Health & social care | 2024 |
| ARC Enforcement Limited | Public administration | 2025 |
| Arcadia Stones Limited | Construction | 2015 |
| Arcady Heights Limited | Construction | 2022 |
| Arch Property Consultancy Limited | Real estate | 2023 |
| Archbold Services Ltd | Professional & scientific | 2016 |
| Archer HR Limited | Administrative & support | 2013 |
| Archetipo Limited | Professional & scientific | 2015 |
| Archian Ltd | Construction | 2024 |
| Archie's Services Ltd | Professional & scientific | 2008 |
| Archipel Capital Limited | Professional & scientific | 2020 |
| Archiplan Design and Management Ltd | Professional & scientific | 2026 |
| Architects Corporation Limited | Professional & scientific | 1995 |
| Architectural Building Works Ltd | Construction | 2024 |
| Archtavisoft Ltd | Information & communication | 2012 |
| Archworx Ltd | Information & communication | 2015 |
| Arco Iris UK Ltd | Extraterritorial | 2008 |
| Arcone Branding Ltd | Professional & scientific | 2025 |
| Arcor Limited | Professional & scientific | 2019 |
| ARD J.L. Ltd | Professional & scientific | 2016 |
| Arden & Dunarden Management Limited | Households | 1999 |
| Arden Grange Property Company Limited | Real estate | 2000 |
| Ardent Tech Services Limited | Information & communication | 2024 |
| ARE YOU GOD Limited | Wholesale & retail | 2026 |
| Area Deluxe Cars Ltd | Transport & logistics | 2022 |
| Area Scaffolding (Watford) Limited | Construction | 2011 |
| Area Signalling Limited | Professional & scientific | 2018 |
| Arematech Ltd | Information & communication | 2024 |
| Arena (ST Albans Road) Management Company Limited | Households | 2005 |
| Aretas Holdings Ltd | Administrative & support | 2024 |
| Aretas Sole Ltd | Administrative & support | 2024 |
| Aretas Trustees Ltd | Administrative & support | 2024 |
| ARF Consultancy Ltd | Professional & scientific | 2025 |
| ARG Leisure Limited | Households | 2019 |
| Argan Invest LP | | 2017 |
| ARH Global Ltd | Transport & logistics | 2020 |
| ARI Holdings Limited | Financial services | 2015 |
| ARI Installations Ltd | Administrative & support | 2004 |
| ARI Rutland Ltd | Information & communication | 2024 |
| Ari&Denis Limited | Transport & logistics | 2020 |
| Aria Aviation Ltd | Education | 2019 |
| Aria Finance Limited | Financial services | 2002 |
| Aria Motorcycles Limited | Wholesale & retail | 2022 |
| Aricorn Essentials Limited | Wholesale & retail | 2024 |
| Aridex Integrated Nigeria Ltd | Administrative & support | 2026 |
| Arient LLP | | 2018 |
| Aries 5 Ltd | Professional & scientific | 2025 |
| Aries Construct Ltd | Construction | 2022 |
| Aries Sun Trading Limited | Real estate | 2012 |
| Arifa Services (London) Limited | Administrative & support | 2014 |
| Arizona Sky Limited | Construction | 2023 |
| ARJ Capital Investments Limited | Financial services | 2020 |
| ARJ Capital Limited | Financial services | 2016 |
| ARJ Electric Ltd | Manufacturing | 2024 |
| Arjun Technosoft Ltd | Information & communication | 2016 |
| ARK Change Management Limited | Information & communication | 1999 |
| ARK Delicious Holdings Ltd | Extraterritorial | 2025 |
| ARK2 Consulting Limited | Professional & scientific | 2017 |
| Arkaim Development Co. Limited | Real estate | 1991 |
| Arkay Contractors Limited | Construction | 2012 |
| Arkay Group Limited | Financial services | 2017 |
| Arkay Group London Limited | Financial services | 2019 |
| Arkay Windows Limited | Construction | 1975 |
| Arkham Studios Ltd | Households | 2022 |
| Arkjoy Risk Consultants Ltd | Financial services | 2022 |
| Arks Housing Limited | Real estate | 2022 |
| Arktech Consultancy Limited | Information & communication | 2010 |
| Arktur LLP | | 2023 |
| Arlington Court (Newmarket) Limited | Real estate | 2007 |
| Arlip Construction Limited | Construction | 2019 |
| Armaan Brar Properties Ltd | Real estate | 2025 |
| Armaan Kidderminster Limited | Real estate | 2025 |
| Armand Electrical Services Ltd Ltd | Energy | 2025 |
| Armanda Property Investments Limited | Real estate | 2017 |
| Armari Limited | Manufacturing | 1994 |
| Armchair Ventures Limited | Information & communication | 2014 |