| Archstyle Limited | Professional & scientific | 2024 |
| Archway Business Solutions Ltd | Manufacturing | 2011 |
| Archway Heritage Ltd | Professional & scientific | 2020 |
| Archway House Management Company Limited | Households | 2014 |
| Archytas Limited | Professional & scientific | 2001 |
| Arcs Property Investments Limited | Real estate | 2021 |
| Arcstone Works Limited | Construction | 2026 |
| Arctic Lion Ltd | Education | 2021 |
| Arculus Cyber Security Limited | Information & communication | 2011 |
| Arculus Limited | Information & communication | 2021 |
| Ardan Recruitment Ltd | Administrative & support | 2026 |
| Arden Fire Ltd | Administrative & support | 2006 |
| Ardent Process Ltd | Professional & scientific | 2022 |
| Ardgadgets Ltd | Wholesale & retail | 2020 |
| Ardour Group Ltd | Wholesale & retail | 2023 |
| Areeva Decor Ltd | Wholesale & retail | 2018 |
| Areeyo Consulting Limited | Administrative & support | 2015 |
| Arena Scaffolding Ltd | Construction | 2018 |
| Ares Kingdom Limited | Real estate | 2023 |
| Arfan Estates Ltd | Real estate | 2026 |
| ARG Electrical Ltd | Construction | 2023 |
| ARG Fencing Ltd | Construction | 2014 |
| Argent & Waugh Limited | Professional & scientific | 2009 |
| Argent Mobile Wash Ltd | Administrative & support | 2023 |
| Argento Consulting Limited | Professional & scientific | 2011 |
| Argentum Financial Planning Limited | Professional & scientific | 2010 |
| Argo Infrastructure Partners LLP | | 2018 |
| Arguibis Ltd | Transport & logistics | 2021 |
| Argyle Community Church Reading | Other services | 2011 |
| Argyle House Management Company Limited | Real estate | 1985 |
| Argyll Business Services Limited | Professional & scientific | 2015 |
| ARH Construction Ltd | Construction | 2024 |
| Arhm Enterprises Ltd | Wholesale & retail | 2025 |
| Arhtim Ltd | Information & communication | 2014 |
| Aria Building Services Limited | Construction | 2004 |
| Aria Quality Solutions Ltd | Professional & scientific | 2021 |
| Ariago Logistics Limited | Transport & logistics | 2026 |
| Aric Transport Ltd | Transport & logistics | 2024 |
| Aridon Property Management Ltd | Hospitality | 2026 |
| Arif Catering Limited | Hospitality | 2002 |
| Arin Traders Limited | Wholesale & retail | 2025 |
| Arise Inspire Health Ltd | Health & social care | 2020 |
| Arise Inspire Ltd | Real estate | 2020 |
| Aristolte Flat Management Compan Y Limited | Households | 1978 |
| Aristos Insight Ltd | Professional & scientific | 2025 |
| ARJ Tax & Payroll Ltd | Professional & scientific | 2015 |
| Arjan United Limited | Real estate | 2020 |
| Arjananiya Ltd | Health & social care | 2022 |
| Arjs Consultants Limited | Information & communication | 2014 |
| Arjun Infrastructure Partners II Limited | Financial services | 2015 |
| Arjun Infrastructure Partners III Limited | Financial services | 2017 |
| Arjun Infrastructure Partners Limited | Financial services | 2015 |
| Arjun Infrastructure Partners Midco Limited | Financial services | 2018 |
| ARK Capital Property Holdings Ltd | Real estate | 2026 |
| ARK Industrial Solutions Limited | Wholesale & retail | 2024 |
| ARK Infovision Limited | Information & communication | 2013 |
| ARK Security Systems Limited | Administrative & support | 2016 |
| ARK Stays Limited | Real estate | 2021 |
| Arka Construction Ltd | Construction | 2023 |
| Arka Consultancy Ltd | Construction | 2024 |
| Arka Property Limited | Real estate | 2024 |
| Arka Technologies Ltd | Information & communication | 2018 |
| Arka-Global Ltd | Professional & scientific | 2025 |
| Arkam Omar Films Ltd | Information & communication | 2022 |
| Arkessa Limited | Information & communication | 2009 |
| Arklo Ltd | Wholesale & retail | 2026 |
| Arkm Property Management Ltd | Real estate | 2021 |
| Arkose Labs UK Limited | Information & communication | 2021 |
| Arkwright (Reading) LLP | | 2011 |
| Arkwright Custom Limited | Financial services | 2023 |
| ARL GAS Ltd | Construction | 2023 |
| ARL Solution Limited | Construction | 2024 |
| Arleigh Group Limited | Professional & scientific | 2004 |
| Arleigh International Limited | Wholesale & retail | 1981 |
| Arleo Biodiversity Limited | Other services | 2025 |
| Arlington Autoworks Ltd | Wholesale & retail | 2025 |
| Arlington Car Sales Ltd | Wholesale & retail | 2019 |
| Arlington Research Limited | Professional & scientific | 2015 |
| Arman D&M Building Ltd | Construction | 2020 |
| Armde'Ot World Ltd | Transport & logistics | 2021 |
| Armitage 18 Solar Limited | Energy | 2021 |
| Armn Advisory Limited | Professional & scientific | 2025 |
| Armor Associates Limited | Information & communication | 2013 |
| Armored Bytes Ltd | Information & communication | 2025 |
| Armour Lodge Management Association RTM Company Limited | Households | 2009 |
| Armour Lodge Management Company Limited | Households | 2007 |
| Armour Road (M.C) Limited | Households | 2019 |
| Armstrong Brickwork Ltd | Construction | 2025 |
| Armstrong Siddeley Heritage Trust Ltd | Other services | 2013 |
| Arnaud's Language Kitchen Limited | Education | 2013 |
| Arnold Property 96 Ltd | Real estate | 2024 |
| Aro&Chefs Ltd. | Hospitality | 2014 |
| Aroa Logistics Ltd | Transport & logistics | 2024 |
| Aroma Antics Ltd | Hospitality | 2025 |
| Aroma Baby Limited | Extraterritorial | 1999 |
| Aroma House Group Ltd | Professional & scientific | 2001 |
| Aroma Mill Ltd | Manufacturing | 2020 |
| Aromark Limited | Extraterritorial | 2000 |
| Arona Hotel Ltd | Hospitality | 2016 |
| Arowena Ltd | Manufacturing | 2023 |