| Aquolla Limited | Real estate | 2015 |
| Aqwa Limited | Construction | 2026 |
| AR Electrics & Sons Limited | Manufacturing | 2021 |
| AR Green Properties Ltd | Real estate | 2023 |
| AR Radiology Ltd | Health & social care | 2020 |
| AR Squared 2020 Limited | Other services | 2020 |
| ARA Mini Market Ltd | Wholesale & retail | 2024 |
| ARA One Healthcare UK Limited | Health & social care | 2025 |
| Arab-Uk Ltd | Professional & scientific | 2017 |
| Arachnys Information Services Limited | Information & communication | 2010 |
| Aralex Consulting Limited | Professional & scientific | 2003 |
| Aras Gandhi Medical Services Ltd | Administrative & support | 2024 |
| Arav Capital Limited | Financial services | 2015 |
| Araya Property Ltd | Real estate | 2020 |
| Araya Skin Clinic Ltd | Other services | 2025 |
| Arbour Property Developments Limited | Construction | 2008 |
| ARC Financial Consultancy Limited | Financial services | 2019 |
| ARC House (Wembley) Management Limited | Households | 2025 |
| ARC Strategy Advisory Ltd | Professional & scientific | 2025 |
| Arcadian Legal Limited | Professional & scientific | 2013 |
| Arcane Group Ltd | Other services | 2020 |
| Arch Builders Ltd | Construction | 2022 |
| Archaea Capital Management Ltd | Real estate | 2021 |
| Archi Plus London Ltd | Construction | 2026 |
| Architect That Limited | Professional & scientific | 2022 |
| Archway DIY Ltd | Wholesale & retail | 2026 |
| Arcr Constructions Ltd | Construction | 2026 |
| Ardleigh Group Ltd | Construction | 2026 |
| Ardmona 1850 Limited | Construction | 2026 |
| Areeba Arslan Ltd | Wholesale & retail | 2026 |
| Aresync Ltd | Information & communication | 2023 |
| Arezzo Homes Limited | Real estate | 2023 |
| ARI Medical Services Ltd | Health & social care | 2022 |
| Aria Housing PVT Ltd | Real estate | 2018 |
| Ariadni Limited | Health & social care | 2022 |
| Ariana Direct Claim Limited | Other services | 2012 |
| Arik Consulting Limited | Other services | 2025 |
| Ariyan Medical Services Limited | Health & social care | 2016 |
| Arizali Limited | Real estate | 2023 |
| Arjo Properties Limited | Real estate | 2023 |
| ARK Advisors Ltd | Professional & scientific | 2018 |
| ARK Exclusive Homes Limited | Real estate | 2017 |
| ARK Property Group Limited | Real estate | 2018 |
| Arkadas Ltd | Real estate | 2017 |
| Arkk Hospitality Limited | Professional & scientific | 2022 |
| Arkrule Construction Limited | Construction | 2020 |
| Arksm Ltd | Hospitality | 2021 |
| Arma Care Investments Limited | Health & social care | 2019 |
| Arma Care Services Limited | Health & social care | 2016 |
| Armstrong & Armstrong (Roofing) Ltd | Construction | 2000 |
| Arniak Global Limited | Professional & scientific | 2026 |
| Arora Testing Experts Ltd | Wholesale & retail | 2017 |
| ARP Investments Limited | Real estate | 2013 |
| Art by 57 Ltd | Arts & recreation | 2020 |
| Artful Hub Ltd | Arts & recreation | 2020 |
| Arti Joshi Creative Limited | Other services | 2017 |
| Article Agency Ltd | Administrative & support | 2016 |
| Artistic Brief Limited | Professional & scientific | 2005 |
| Artnam Consulting Limited | Professional & scientific | 2022 |
| Arts in Rural Gloucestershire | Arts & recreation | 2001 |
| Artsplit Limited | Wholesale & retail | 2021 |
| Arulnanthy GP Services Ltd | Other services | 2010 |
| Arushita Property Limited | Real estate | 2020 |
| ARV Investments Ltd | Real estate | 2020 |
| Arven Holdings Group Ltd | Financial services | 2020 |
| Arvika Homes Ltd | Real estate | 2022 |
| ARY Properties Ltd | Real estate | 2020 |
| Arya Properties Limited | Real estate | 2016 |
| Aryana Ltd | Information & communication | 2015 |
| Aryav Consulting Ltd. | Information & communication | 2012 |
| Aryel Business and Technology Consulting Ltd | Professional & scientific | 2021 |
| AS Design Studio Limited | Professional & scientific | 2017 |
| As&K Commercial Properties 2 Ltd | Real estate | 2025 |
| As&K Commercial Properties Ltd | Real estate | 2012 |
| Asana Healthcare Ltd | Health & social care | 2019 |
| Ascot Accountancy Limited | Professional & scientific | 2019 |
| Ascot Interiors Limited | Administrative & support | 1984 |
| Asees Homes Ltd | Real estate | 2020 |
| Asgava Ltd | Wholesale & retail | 2023 |
| ASH & DAN Associates Ltd | Real estate | 2023 |
| ASH RIJ Edtech Limited | Information & communication | 2025 |
| ASH RIJ Foods Limited | Hospitality | 2023 |
| ASH RIJ Health Care Limited | Health & social care | 2023 |
| ASH Saluja Holdings Limited | Financial services | 2025 |
| ASH Saluja Limited | Professional & scientific | 2019 |
| Asha Mortgage Solutions Limited | Financial services | 2020 |
| Asha Solutions Limited | Professional & scientific | 2012 |
| Ashapura Associates Limited | Extraterritorial | 1997 |
| Ashapura Consultants Limited | Extraterritorial | 2009 |
| Ashaw Medical Ltd | Health & social care | 2026 |
| Ashbel Limited | Wholesale & retail | 2003 |
| Ashbrook 1-4 (Management Company) Limited | Households | 2018 |
| Ashbrook 9-12 (Management Company) Limited | Households | 2016 |
| Ashburton Care Limited | Health & social care | 2020 |
| Ashco Holdings Limited | Administrative & support | 2004 |
| Ashglen Investments Limited | Real estate | 2024 |
| Ashh (53) Enterprises Limited | Real estate | 2024 |
| Ashh Engineering (53) Ltd | Professional & scientific | 2017 |
| Ashish Marwaha Consulting Ltd | Information & communication | 2026 |
| Ashley Bond Ltd | Information & communication | 2025 |