| Arlington Park South Ltd | Real estate | 2021 |
| Arlix Ltd | Wholesale & retail | 2025 |
| ARM Investments Ltd | Construction | 2026 |
| ARM Petts Wood Ltd | Hospitality | 2015 |
| Armadillo Properties Ltd | Real estate | 2025 |
| Armfield Financial Ltd | Financial services | 2019 |
| Armfield Offshore PCS Limited | Mining & quarrying | 2014 |
| Arminghall Catering Limited | Hospitality | 2017 |
| Arminghall Fields Management Company Limited | Households | 2022 |
| Armour Coachworks Ltd | Information & communication | 2022 |
| Armstrong Capital Management Limited | Financial services | 2018 |
| Armstrong Design Limited | Professional & scientific | 2000 |
| Armstrong Elliott Limited | Professional & scientific | 2009 |
| Armstrong Energy Global Limited | Energy | 2013 |
| Armstrong Energy Limited | Energy | 2012 |
| Armstrong Infrastructure and Property Finance Limited | Financial services | 2016 |
| Armtree Ltd | Professional & scientific | 2002 |
| Arnella Limited | Professional & scientific | 2021 |
| Arnold Business Services Limited | Administrative & support | 1984 |
| Arnold Read Property Limited | Real estate | 2018 |
| Arnolds Keys LLP | | 2010 |
| Arolet Limited | Real estate | 2025 |
| Aron Estates Ltd | Real estate | 2020 |
| Arotron Ltd | Other services | 2014 |
| ARP Testing Services Ltd | Mining & quarrying | 2014 |
| Arqtic Ltd | Professional & scientific | 2025 |
| Arquata Ltd | Manufacturing | 2021 |
| Arran Dennis Ltd | Agriculture & fishing | 2024 |
| Arrhenius Holdings Limited | Professional & scientific | 2010 |
| Arrisauto Limited | Wholesale & retail | 2017 |
| Arrivy Ltd | Transport & logistics | 2025 |
| Arron Scaffolding Limited | Construction | 2017 |
| Arrow Headz Ltd | Wholesale & retail | 2024 |
| Arrow Taxis (Essex) Limited | Transport & logistics | 2008 |
| Arrowland Holdings Ltd | Real estate | 2021 |
| ARS Rubber Company Ltd | Wholesale & retail | 2022 |
| Arshia Luton Ltd | Hospitality | 2018 |
| Arslans Catering Ltd | Hospitality | 2024 |
| Arsov Corporation Ltd | Transport & logistics | 2023 |
| Art 4 Youth CIC | Education | 2017 |
| Art Angels Publishing Limited | Manufacturing | 2011 |
| Art Exclusive Limited | Arts & recreation | 2018 |
| Art House Norwich CIC | Education | 2026 |
| Art of Dark Ltd | Arts & recreation | 2018 |
| Art of Flour Ltd | Hospitality | 2019 |
| Art of Frying Ltd | Hospitality | 2016 |
| Art of the Jackdaw Limited | Arts & recreation | 2013 |
| Art Renewables Plumbing & Heating Ltd | Construction | 2018 |
| ART2GOVERNANCE Ltd | Administrative & support | 2025 |
| Artage Publishers Limited | Information & communication | 2011 |
| Artatwork CIC | Education | 2017 |
| Artemis IT Solutions Limited | Professional & scientific | 2017 |
| Arterisk Limited | Information & communication | 2025 |
| Artharla Collection Ltd | Financial services | 2026 |
| Arthur Brook (Dewsbury) Limited | Water & waste | 1957 |
| Arthur Stanley Property Investments Limited | Real estate | 2025 |
| Arthur Warring Ltd | Professional & scientific | 2025 |
| Arthur Wheeler & Co. Limited | Extraterritorial | 2018 |
| Arthur's Properties Limited | Real estate | 2025 |
| Artichoke Beer Company Limited | Hospitality | 2024 |
| Article Holdings Ltd | Extraterritorial | 2021 |
| Artillery Meadow (Kelsale) Limited | Households | 2021 |
| Arting Around CIC | Education | 2024 |
| Artisan Renovations (Norfolk) Ltd | Construction | 2024 |
| Artist in Italy Ltd | Arts & recreation | 2014 |
| Artlist UK Limited | Information & communication | 2001 |
| Arto IT Solutions Limited | Information & communication | 2026 |
| Artrya UK Limited | Professional & scientific | 2022 |
| Arts Table Norwich CIC | Education | 2026 |
| Artt Properties Limited | Real estate | 2025 |
| ARW Wealth Managers Ltd | Extraterritorial | 2001 |
| Arwel Douglas Leadership Limited | Professional & scientific | 2018 |
| AS Formations Ltd | Extraterritorial | 2022 |
| AS Mini Mart Ltd | Wholesale & retail | 2025 |
| AS Property Development Norfolk Ltd | Construction | 2020 |
| AS Reynolds Limited | Wholesale & retail | 2017 |
| AS Student Homes Ltd | Real estate | 2022 |
| As-Art-Co CIC | Administrative & support | 2021 |
| AS31 Limited | Wholesale & retail | 2024 |
| Asap Properties (UK) Limited | Professional & scientific | 2013 |
| Asats Limited | Construction | 2001 |
| ASB Music Ltd | Administrative & support | 2016 |
| Asbestos Norwich Limited | Water & waste | 2024 |
| Asbestos Survey Solutions Ltd | Professional & scientific | 2011 |
| Ascend Airways Limited | Transport & logistics | 2004 |
| Ascend Technology Holdings Limited | Financial services | 2025 |
| Ascendia OS Ltd | Information & communication | 2026 |
| Ascendly Limited | Professional & scientific | 2025 |
| Ascension 1543 Ltd | Hospitality | 2020 |
| Ascent Acquisitions Ltd | Financial services | 2025 |
| Ascher Consulting Limited | Professional & scientific | 2019 |
| Ascotglobe Limited | Information & communication | 1982 |
| Asdak Limited | Financial services | 2000 |
| Asenov Transport Ltd | Transport & logistics | 2017 |
| ASF Medical Limited | Health & social care | 2026 |
| ASG Heating Ltd | Construction | 2025 |
| ASH and Tanya Ltd | Arts & recreation | 2025 |
| ASH Close (Wymondham) Management Limited | Households | 2022 |
| ASH Developments Norfolk Ltd | Real estate | 2025 |
| ASH Soan Limited | Arts & recreation | 2012 |