| Aqua Cleanse (Gloucester) Limited | Other services | 2022 |
| Aqua Construction Limited | Construction | 2000 |
| Aqua Horse Ltd | Hospitality | 2025 |
| Aqua Pura Consultancy Ltd | Professional & scientific | 2025 |
| Aquaequi Ltd | Education | 2023 |
| Aquatech Survey Limited | Professional & scientific | 2010 |
| AR Mobile Care Ltd. | Other services | 2019 |
| AR Property Holdings Ltd | Real estate | 2024 |
| AR Remediations Limited | Mining & quarrying | 2022 |
| ARB Design Ltd | Professional & scientific | 2022 |
| Arbanlay LLP | | 2021 |
| Arbol INS Services (UK) Ltd | Financial services | 2023 |
| Arborcraft Ltd | Agriculture & fishing | 2019 |
| ARC Compliance Consultants Ltd | Administrative & support | 2018 |
| ARC Images Ltd | Information & communication | 2019 |
| ARC Property Investors Ltd | Construction | 2026 |
| Arcane House Ltd | Information & communication | 2019 |
| Arcexi Ltd | Other services | 2022 |
| Arch Pro Ltd | Extraterritorial | 2023 |
| Archenfield Investments Limited | Real estate | 2024 |
| Architectural Services (UK) Limited | Professional & scientific | 2009 |
| Archon Logistics Ltd | Transport & logistics | 2023 |
| Archuarjan Ltd | Real estate | 2023 |
| Archway Builders Ltd | Real estate | 2018 |
| Ardencote Pigs Limited | Professional & scientific | 1977 |
| Ardent Staff Ltd | Administrative & support | 2013 |
| Ardent Supported Living Services Limited | Health & social care | 2020 |
| Ardley Limited | Wholesale & retail | 1983 |
| Area XIV Limited | Real estate | 2026 |
| Argus Group Ltd | Public administration | 2019 |
| Ariana Store Ltd | Wholesale & retail | 2024 |
| Aristos Partnership Limited | Information & communication | 2016 |
| Arkai Consultancy Ltd | Professional & scientific | 2024 |
| Arkon Landscape Design Company Ltd | Professional & scientific | 2025 |
| Arkyne Ltd | Education | 2026 |
| ARL Plastering and Rendering Ltd | Construction | 2024 |
| Arlemi Limited | Information & communication | 2017 |
| Arlingham Developments Limited | Construction | 2015 |
| Arlingham Investments Limited | Real estate | 1978 |
| Arlingham Properties Limited | Construction | 2018 |
| Arlington & ROW Limited | Real estate | 2025 |
| Arlington and ROW Events Limited | Administrative & support | 2025 |
| Arlun Groundworks Ltd | Construction | 2021 |
| Armaan Ventures Limited | Real estate | 2023 |
| Armada Bidco Limited | Financial services | 2020 |
| Armada Midco Limited | Financial services | 2020 |
| Armada Topco Limited | Financial services | 2020 |
| Armoured Combat Limited | Arts & recreation | 2021 |
| Armscroft Developments Ltd | Construction | 2019 |
| Armscroft Holdings Limited | Professional & scientific | 2025 |
| Armscroft Properties Ltd | Real estate | 2018 |
| Armstrong Storage & Packaging Ltd | Transport & logistics | 2009 |
| Armton Fleet Ltd | Transport & logistics | 2025 |
| Armton Group Ltd | Information & communication | 2025 |
| Armton Tech Ltd | Wholesale & retail | 2025 |
| Aromatic Herbal Shop Ltd | Wholesale & retail | 2020 |
| Arqtech IT Solutions Limited | Information & communication | 2022 |
| Arriva Building Supplies Limited | Extraterritorial | 2015 |
| Arriva Capital Limited | Administrative & support | 2018 |
| Arriva Care Limited | Extraterritorial | 2009 |
| Arriva Care Services Limited | Health & social care | 2007 |
| Arriva Construction Limited | Extraterritorial | 2015 |
| Arriva Digital Limited | Information & communication | 2019 |
| Arriva Global Exports Limited | Extraterritorial | 2016 |
| Arriva Global Imports Limited | Extraterritorial | 2016 |
| Arriva Global Limited | Extraterritorial | 2016 |
| Arriva Global Plant Sales Limited | Wholesale & retail | 2016 |
| Arriva Global Sales Limited | Extraterritorial | 2016 |
| Arriva Global Trading Limited | Extraterritorial | 2016 |
| Arriva Group Limited | Financial services | 1998 |
| Arriva Healthcare Limited | Extraterritorial | 2015 |
| Arriva Holdings Limited | Financial services | 2009 |
| Arriva Homes Limited | Construction | 2019 |
| Arriva Logistics Limited | Extraterritorial | 2016 |
| Arriva Planning Limited | Professional & scientific | 2018 |
| Arriva Plant Sales Limited | Extraterritorial | 2016 |
| Arriva Recruitment Limited | Extraterritorial | 2009 |
| Arriva Residential Limited | Extraterritorial | 2009 |
| Arriva Stadium Limited | Extraterritorial | 2010 |
| Arriva Stone Supplies Limited | Extraterritorial | 2015 |
| Arriva Technology Limited | Information & communication | 2018 |
| Arriva Training Limited | Education | 2015 |
| Arrivabuild Limited | Extraterritorial | 2016 |
| Arrk Product Development Group Limited | Financial services | 1988 |
| ARS Automotive Ltd | Wholesale & retail | 2026 |
| ARS Medica Ltd | Health & social care | 2020 |
| Arsr Enterprises Limited | Professional & scientific | 2013 |
| Art Property Holdings Ltd | Real estate | 2023 |
| Artificial Images 2020 Ltd | Wholesale & retail | 2019 |
| Artisan Aesthetics Ltd | Health & social care | 2018 |
| Artisan Blooms Ltd | Wholesale & retail | 2021 |
| Artles Trades Ltd | Financial services | 2025 |
| Arts Diverse-City Community Interest Company | Education | 2022 |
| Artémi Homes Ltd | Hospitality | 2025 |
| Arvesse Limited | Wholesale & retail | 2022 |
| Arwim Property Ltd | Real estate | 2024 |
| AS Travel (Gloucestershire) Limited | Transport & logistics | 2024 |
| ASA Electrical Contractors Limited | Construction | 2025 |
| ASA Electrical Services Limited | Construction | 2015 |
| ASA Hospitality Limited | Hospitality | 2021 |