| ARC Architecture Ltd | Professional & scientific | 1990 |
| ARC Cleaners Limited | Administrative & support | 2026 |
| ARC Digital Limited | Administrative & support | 2014 |
| ARC Precision Ltd | Manufacturing | 2026 |
| Arca Developments Ltd | Manufacturing | 2025 |
| Arcana Holistic Skin Treatments Ltd | Other services | 2022 |
| Arcata Developments Limited | Construction | 2021 |
| Arcbro UK Ltd | Wholesale & retail | 2021 |
| Arch Construction Systems (SW) Ltd | Construction | 2024 |
| Archangel Loafers Ltd | Wholesale & retail | 2025 |
| Archenfeld Limited | Administrative & support | 2016 |
| Archer Carpentry Loft Conversions Ltd | Manufacturing | 2023 |
| Archer Marine Limited | Manufacturing | 2024 |
| Archer's Property Developments Limited | Construction | 2025 |
| Archet Limited | Real estate | 2023 |
| Archibald Promotions Ltd | Arts & recreation | 2017 |
| Archikadia Invest SP. Z O.O. Ltd | Construction | 2020 |
| Archiving Online Ltd | Administrative & support | 2019 |
| Archonix Arts Ltd | Information & communication | 2020 |
| Archtek Services Limited | Construction | 2015 |
| Archway Property Solutions Ltd | Households | 2020 |
| Arcn Limited | Information & communication | 2014 |
| Ardacagan Limited | Real estate | 2026 |
| Arden Vale Partners Ltd | Professional & scientific | 2025 |
| Ardent Marine Ltd | Transport & logistics | 2015 |
| Ardent Ronin Consulting Ltd | Information & communication | 2017 |
| Ardent Technology Limited | Information & communication | 2005 |
| Ardia Digital Health Ltd. | Administrative & support | 2016 |
| Ardmore Road Management Limited | Real estate | 2009 |
| ARE WE Human Ltd | Information & communication | 2026 |
| Argentum Solutions Limited | Information & communication | 2011 |
| Argo Homes Ltd | Construction | 2017 |
| Argo Homes Property Group Limited | Real estate | 2022 |
| Argon Welding Ltd | Manufacturing | 2008 |
| Argyle Organic Ltd | Hospitality | 2022 |
| Argyll Automation Ltd | Professional & scientific | 2025 |
| Argyll Stuart Limited | Information & communication | 2013 |
| ARI Data Services Ltd | Information & communication | 2022 |
| Aricoma Limited | Real estate | 2017 |
| Arix Limited | Wholesale & retail | 2014 |
| ARK Group Holdings Limited | Financial services | 2024 |
| ARK Harbour Ltd | Real estate | 2023 |
| Arkdropss Ltd | Wholesale & retail | 2024 |
| Arkiplan Architectural Limited | Professional & scientific | 2019 |
| Arkmil Limited | Transport & logistics | 2023 |
| Arkturian Limited | Wholesale & retail | 2022 |
| Arleta Wrob Ltd | Administrative & support | 2017 |
| Arlington & Hall Limited | Professional & scientific | 2010 |
| Arlo Property Services Ltd | Households | 2022 |
| Armado BIS. Ltd | Transport & logistics | 2025 |
| Arno Bathrooms Ltd | Wholesale & retail | 2022 |
| Arnold Precision Engineering Limited | Professional & scientific | 2018 |
| Arpeggio DUO Limited | Other services | 2026 |
| Arpegio Services Limited | Administrative & support | 2026 |
| Arrival Labs Ltd | Information & communication | 2023 |
| Arrive Homes Limited | Real estate | 2022 |
| Arrivepay Limited | Wholesale & retail | 2025 |
| Arrow BC Ltd | Information & communication | 2026 |
| Arrow Companies Ltd | Financial services | 2022 |
| Arrow Energy Solutions Ltd | Construction | 2024 |
| Arrow Homes Ltd | Real estate | 2022 |
| Arrowcrest LLP | | 2013 |
| ARS Nature Ltd | Manufacturing | 2026 |
| Art Fever Limited | Manufacturing | 2004 |
| Art Light Films Limited | Information & communication | 2009 |
| Art NOT Evidence Limited | Education | 2024 |
| Art With a Design Ltd | Wholesale & retail | 2022 |
| Artemis Consultancy Ltd | Professional & scientific | 2019 |
| Artemis Insolvency Services Limited | Professional & scientific | 2011 |
| Artena Solutions Ltd | Information & communication | 2007 |
| Artesienne Limited | Other services | 2025 |
| Artful Assemblage Limited | Information & communication | 2019 |
| Arthur Bray Limited | Real estate | 1970 |
| Arthur Court RTM Company Limited | Real estate | 2011 |
| Arthur H. LEE & Sons Ltd | Manufacturing | 2020 |
| Arthur Hoskins Ltd | Manufacturing | 2024 |
| Artificial Entertainment Limited | Information & communication | 2022 |
| Artificial Intelligence LAB Ltd | Information & communication | 2020 |
| Artigen Limited | Information & communication | 2023 |
| Artis DEV Ltd | Information & communication | 2019 |
| Artisan Ginyard Ltd | Extraterritorial | 2017 |
| Artisan Property Solutions Ltd | Construction | 2020 |
| Arts Detailing Limited | Administrative & support | 2021 |
| Arts for Survival Community Interest Company | Education | 2017 |
| Arty Focus Limited | Education | 2011 |
| ARV Ventures Limited | Real estate | 2025 |
| Arvantium Ltd | Information & communication | 2024 |
| Aryzetech Ltd | Wholesale & retail | 2025 |
| Arzkade Ltd | Information & communication | 2025 |
| AS Dhillon Logistics Ltd | Transport & logistics | 2025 |
| AS Easy AS CBD Ltd | Wholesale & retail | 2019 |
| AS Ecom Ltd | Wholesale & retail | 2025 |
| AS Medical Limited | Health & social care | 2006 |
| AS Social Creative Ltd | Professional & scientific | 2026 |
| Asad Empire Ltd | Wholesale & retail | 2025 |
| Asante Property Group Ltd | Real estate | 2023 |
| Asbestos Contracting Limited | Water & waste | 2012 |
| ASC Process Systems Limited | Wholesale & retail | 2010 |
| Ascend Support (South) Limited | Health & social care | 2019 |
| Ascend Support Limited | Health & social care | 2021 |