| Aquafilta Limited | Water & waste | 2014 |
| Aqualeo Consulting Ltd | Information & communication | 2020 |
| Aqualeo Limited | Wholesale & retail | 2010 |
| Aqualine UK Solutions Ltd | Wholesale & retail | 2024 |
| Aquamarine Property Ltd | Real estate | 2017 |
| Aquaoils Ltd | Wholesale & retail | 2024 |
| Aquaplumb Solutions Ltd | Construction | 2013 |
| Aquarius Cleaning Equipment Ltd | Administrative & support | 2008 |
| Aquarius Contracts Ltd | Construction | 1998 |
| Aquaspray Fire Protection Ltd | Construction | 2009 |
| Aquayell Ltd | Water & waste | 2023 |
| AR Constructors Ltd | Construction | 2022 |
| AR Creators Media Ltd | Information & communication | 2025 |
| AR Equity Ltd | Real estate | 2025 |
| AR Shopfronts Ltd | Construction | 2021 |
| Arab Society for Paediatric Endocrinology and Diabetes | Other services | 2026 |
| Aradia Ltd | Wholesale & retail | 2019 |
| Araf Trading Ltd | Real estate | 2025 |
| Araks Barbers Ltd | Other services | 2017 |
| Arami London Ltd | Other services | 2025 |
| Aran Associates Ltd | Professional & scientific | 2023 |
| Arapaima Glow Ltd | Wholesale & retail | 2025 |
| Aras Talha Ltd | Hospitality | 2025 |
| Arbm Enterprises Ltd | Health & social care | 2025 |
| Arbogen Ltd | Information & communication | 2024 |
| Arboracre Developments Limited | Real estate | 2010 |
| Arborterra Ltd | Professional & scientific | 2016 |
| ARC Cider Limited | Manufacturing | 2023 |
| ARC Erith Group Limited | Wholesale & retail | 2025 |
| ARC Hi-Voltage Services Ltd | Manufacturing | 2024 |
| ARC Management Systems Consulting Limited | Information & communication | 2026 |
| ARC Properties (Suffolk) Limited | Real estate | 2020 |
| ARC SEN Family Support CIC | Health & social care | 2025 |
| ARC Systems Technology Limited | Administrative & support | 2011 |
| Arch Property Holdings Limited | Real estate | 2025 |
| Archaean Ltd | Agriculture & fishing | 2023 |
| Archers Place Residents' Management Company Ltd | Households | 2017 |
| Arches Entertainments Limited | Hospitality | 2008 |
| Archiai Solution Ltd | Information & communication | 2025 |
| Archii Ltd | Information & communication | 2026 |
| Archilab Ltd | Professional & scientific | 2024 |
| Archipelagos Pictures Ltd | Information & communication | 2025 |
| Architects UW Ltd | Professional & scientific | 2008 |
| Archo Commerce Ltd | Wholesale & retail | 2025 |
| Archwise Limited | Wholesale & retail | 2025 |
| Arctic OWL Ltd | Professional & scientific | 2011 |
| ARD Plant Hire Ltd | Water & waste | 2025 |
| ARD Recycling Ltd | Water & waste | 2021 |
| Arden Property Holdings Group Limited | Real estate | 2025 |
| Aren Jewellery Limited | Wholesale & retail | 2024 |
| Areyoufaster CIC | Information & communication | 2025 |
| Arfan ALI Ltd | Health & social care | 2022 |
| Arhan Limited | Hospitality | 2020 |
| Aria International Services Ltd | Wholesale & retail | 2018 |
| Aria Starlight Pictures Ltd | Information & communication | 2026 |
| Ariadne Properties Ltd | Real estate | 2020 |
| Ariadnes Ltd | Hospitality | 2026 |
| Ariel Bikes Ltd | Manufacturing | 2020 |
| Arinze Antigha Okosieme | Extraterritorial | 2024 |
| Aris R. Ltd | Other services | 2025 |
| Arise Scaffolding Ltd | Construction | 2026 |
| Arive Group Ltd | Transport & logistics | 2026 |
| ARK & River Group Ltd | Real estate | 2019 |
| ARK Electrical Contracts Limited | Manufacturing | 2013 |
| Arkemis Ltd | Financial services | 2025 |
| Arkk Services Ltd | Information & communication | 2025 |
| Arkle Storage Ltd | Transport & logistics | 2023 |
| Arkmp Holdings Limited | Financial services | 2025 |
| Arkowear Ltd | Wholesale & retail | 2025 |
| Arlington & Persch Ltd | Wholesale & retail | 2026 |
| Arlo Building and Landscapes Ltd | Administrative & support | 2026 |
| ARM Acquisitions Ltd | Real estate | 2025 |
| Armada Ltd | Professional & scientific | 2017 |
| Armantini Processing Limited | Manufacturing | 2007 |
| Armstrong Broadcast Antennas Limited | Information & communication | 2020 |
| Armstrongs Funeral Service Limited | Other services | 2005 |
| Arnhem (Group) Limited | Wholesale & retail | 2025 |
| Arnold's Enterprises Limited | Financial services | 2020 |
| Arosi Limited | Information & communication | 2025 |
| ARQ Roofing Services Ltd | Construction | 2022 |
| Arranmore Construction Limited | Construction | 2014 |
| Arrivist IT Solutions Limited | Information & communication | 2011 |
| Arrow One Ventures Limited | Real estate | 2025 |
| Arrowcraft Limited | Transport & logistics | 2024 |
| Arrowhead Security Ltd | Administrative & support | 2022 |
| Arrowrock Ltd | Professional & scientific | 2025 |
| Arrows Enterprise Limited | Wholesale & retail | 2022 |
| Arsha Accountants and IT Solutions Ltd | Information & communication | 2026 |
| Arslan Stores Ltd | Wholesale & retail | 2024 |
| Art Musey Ltd | Information & communication | 2024 |
| Art of Beauty Cafe Ltd | Wholesale & retail | 2025 |
| Art of Flight Ltd | Professional & scientific | 2023 |
| Artava Jewellers Ltd | Wholesale & retail | 2024 |
| Artdigita Ltd | Information & communication | 2017 |
| Artefact Brewing Ltd | Manufacturing | 2019 |
| Artega Limited | Information & communication | 2024 |
| Artemis Praesepe Productions Ltd | Extraterritorial | 2025 |
| Artfall Ltd | Information & communication | 2026 |
| Artfix Renovation Ltd | Construction | 2019 |
| Arthur & Associates Ltd | Real estate | 2025 |