| ARA Counselling Limited | Health & social care | 2019 |
| ARA Global Enterprises Ltd | Information & communication | 2021 |
| Arabaroma Ltd | Wholesale & retail | 2025 |
| Arabic Heritage Ltd | Education | 2023 |
| Arafah CH Ltd | Wholesale & retail | 2025 |
| Araknet Limited | Information & communication | 2017 |
| Aram International INT Ltd | Wholesale & retail | 2025 |
| ARB Consultants Ltd | Agriculture & fishing | 2007 |
| ARB Intelligent Tree Surveying Ltd | Administrative & support | 2025 |
| ARB Science Limited | Professional & scientific | 2024 |
| Arbour Joinery & Building Ltd | Construction | 2025 |
| ARC Accountancy Limited | Professional & scientific | 2010 |
| ARC and SMC Holdings Limited | Households | 2023 |
| ARC Right Pyrotechnics Ltd | Arts & recreation | 2024 |
| ARC Right Services Ltd | Manufacturing | 2020 |
| Arcas Elephant Building Limiited Limited | Construction | 2021 |
| Arcf Test Company Limited | Agriculture & fishing | 2021 |
| Arch Finance Ltd | Administrative & support | 2018 |
| Archangel Professional Services Ltd | Information & communication | 2023 |
| Archangel Software Limited | Information & communication | 2018 |
| Arche Engineering Group Ltd | Professional & scientific | 2026 |
| Archetype Financial Planning Limited | Professional & scientific | 2023 |
| Archiedora Holdings Ltd | Financial services | 2021 |
| Archifoliokt Ltd | Professional & scientific | 2020 |
| Architectural Services (NW) Limited | Professional & scientific | 2012 |
| Archlight Studio Ltd | Professional & scientific | 2026 |
| Archway Building Pedders Lane Management Company Limited | Households | 2003 |
| Arco Organics Ltd | Wholesale & retail | 2025 |
| Arctic Brands Ltd | Wholesale & retail | 2021 |
| Arctic Prism Ltd | Information & communication | 2022 |
| Arcware Architectural Limited | Wholesale & retail | 2004 |
| Arden LEA Group Limited | Administrative & support | 2008 |
| Ardenia Estate Ltd | Real estate | 2021 |
| Ardstocks Limited | Wholesale & retail | 2024 |
| Area Health Information Services Limited | Professional & scientific | 1995 |
| AREESH29 Ltd | Wholesale & retail | 2026 |
| Arena Investment Management Limited | Financial services | 1960 |
| Ares Marketing Ltd | Professional & scientific | 2023 |
| ARES360 CIC | Education | 2025 |
| Aretha Capital Partners Ltd | Professional & scientific | 2018 |
| Arfaat Ecom Ltd | Wholesale & retail | 2023 |
| Argill Properties Ltd | Real estate | 2023 |
| Argram Limited | Professional & scientific | 2009 |
| Argyll State Preston Ltd | Real estate | 2026 |
| ARH & Partners Ltd | Real estate | 2023 |
| Ari.Ash Ltd | Real estate | 2020 |
| Aria Grace Investments Limited | Real estate | 2021 |
| Arida Fastfood Ltd | Hospitality | 2026 |
| Arjun Foods Ltd | Hospitality | 2025 |
| ARK Broker Services Ltd | Information & communication | 2019 |
| ARK Healthcare Solutions Ltd | Real estate | 2011 |
| ARK Legal Limited | Professional & scientific | 2017 |
| ARK Management Ltd | Real estate | 2017 |
| ARK Padel Limited | Arts & recreation | 2026 |
| Arkana Rama Ltd | Information & communication | 2025 |
| Arkern Ltd | Information & communication | 2026 |
| Arlington Davies Ltd | Extraterritorial | 2006 |
| Armaplate (UK) Ltd | Manufacturing | 1997 |
| Armitstead Barnett Financial Services Limited | Financial services | 2002 |
| Armoured Auto Detailing Limited | Administrative & support | 2024 |
| Army Ants Removers Ltd | Transport & logistics | 2016 |
| Army Ants Storage Ltd | Transport & logistics | 2016 |
| Arndale Estate Ltd | Real estate | 2026 |
| Arnish Moor Wind Farm Limited | Energy | 2014 |
| Arnlap Limited | Extraterritorial | 1988 |
| ARO Trading Ltd | Other services | 2019 |
| Arpeggio Properties Limited | Hospitality | 2012 |
| Arran Bradford Holdings Limited | Real estate | 2026 |
| Arranmore Park Limited | Administrative & support | 2004 |
| Arranpaul Audio Limited | Arts & recreation | 2001 |
| Arriv Ltd | Information & communication | 2026 |
| Arrk Property Ltd | Real estate | 2015 |
| Arro Engineering Limited | Professional & scientific | 2025 |
| Arrokoth Design Ltd | Information & communication | 2022 |
| Arron & Kearsley Homes Limited | Real estate | 2017 |
| Arrow Building Limited | Construction | 2021 |
| Arrowsmith Care Homes Limited | Health & social care | 2016 |
| Arrowsmith Rest Homes Limited | Health & social care | 2004 |
| Arrowsmith Utilities Limited | Construction | 2015 |
| ARS Dent Services Limited | Health & social care | 2025 |
| Arshad Chicken Limited | Hospitality | 2023 |
| Art Construct & Cleaner Ltd | Construction | 2026 |
| Art School by Subscription Ltd | Education | 2024 |
| Art With Stone Ltd | Manufacturing | 2023 |
| Artesano Hospitality Limited | Hospitality | 2025 |
| Arthro-Vite Limited | Manufacturing | 1994 |
| Arthur's Garage Ltd | Wholesale & retail | 2016 |
| Arti Garden Limited | Administrative & support | 2020 |
| Artifex Building Solutions Limited | Construction | 2016 |
| Artificial Grass Online Ltd | Wholesale & retail | 2016 |
| Artisan Deli Limited | Hospitality | 2021 |
| Artlab Films Limited | Information & communication | 2013 |
| Artley Systems Engineering Ltd | Professional & scientific | 2012 |
| Artur Szewc Managment & Consulting Ltd | Professional & scientific | 2024 |
| Arty Discoverers Limited | Education | 2024 |
| Arundel Lifestyle Limited | Wholesale & retail | 2021 |
| Arveno Fitness Ltd | Information & communication | 2026 |
| ARW Enrol Limited | Professional & scientific | 2014 |
| Arwel Douglas Performance Limited | Professional & scientific | 2018 |
| Aryan Trader Limited | Wholesale & retail | 2023 |