| Arena Hand Car Wash Ltd | Other services | 2018 |
| Arena Tyres Ltd | Wholesale & retail | 2015 |
| Arevcruz Ltd | Wholesale & retail | 2026 |
| Argentum RE Ltd | Real estate | 2017 |
| Argi Medical Ltd | Health & social care | 2022 |
| Argon (Cathedral Park) Management Company Limited | Real estate | 2004 |
| Argon (NES 1) Limited | Extraterritorial | 2024 |
| Argon Health (Seaton Delaval) Ltd | Extraterritorial | 2024 |
| Argon Health Ltd | Real estate | 2019 |
| Argon Primary Care Ltd | Real estate | 2024 |
| Argon Properties Ltd | Construction | 2001 |
| Argon Property Development Solutions Ltd | Real estate | 2020 |
| Argyle Plumbing and Heating Solutions Ltd | Construction | 2015 |
| Argyle Property Services Ltd | Construction | 2023 |
| Aria Core Limited | Information & communication | 2026 |
| Aria Property Limited | Real estate | 2019 |
| Arifeen Property Developments Ltd | Real estate | 2016 |
| Ariha Ltd | Wholesale & retail | 2025 |
| Arija Ltd | Real estate | 2025 |
| Arimos Pest Control Ltd | Administrative & support | 2016 |
| Arioo Ltd | Hospitality | 2019 |
| Arios Barber Limited | Other services | 2022 |
| Aripo Global Limited | Households | 2025 |
| Arise Mortgages Ltd | Financial services | 2026 |
| Arisop Ltd | Real estate | 2023 |
| Aristocrat Exclusive Ladies and Menswear Limited | Wholesale & retail | 1991 |
| Arjo.Dev Ltd | Information & communication | 2023 |
| Arjuna Technologies Limited | Information & communication | 2002 |
| Arjw Events Ltd | Arts & recreation | 2026 |
| ARK Property Developments Ltd | Real estate | 2016 |
| Ark-Iy Ltd | Wholesale & retail | 2024 |
| Arka Learning Limited | Administrative & support | 2023 |
| Arkan Foods Ltd | Hospitality | 2020 |
| Arkchimos Ltd | Wholesale & retail | 2025 |
| Arkitec Software Limited | Information & communication | 2005 |
| Arko Services Ltd | Construction | 2022 |
| Arks Industries Ltd | Professional & scientific | 2025 |
| Arlenia Limited | Financial services | 2024 |
| Arlington* Records Ltd. | Information & communication | 2024 |
| Arlot Media Ltd | Professional & scientific | 2023 |
| ARM Energy Assessors Limited | Professional & scientific | 2008 |
| Armaan & ANA Properties Ltd | Real estate | 2025 |
| Armamentarium Ltd | Information & communication | 2021 |
| Armarium Crown Ltd | Manufacturing | 2020 |
| Armarium Partnership Ltd | Professional & scientific | 2020 |
| Armatrex Ltd | Health & social care | 2017 |
| Armes-Reardon Properties Limited | Real estate | 2012 |
| Armitage Court Limited | Construction | 2018 |
| Armitage Lettings LLP | | 2020 |
| Armkirk Ltd | Manufacturing | 2008 |
| Armour-Tec Plumbing and Heating Ltd | Construction | 2017 |
| Armson Engineering Limited | Manufacturing | 2020 |
| Armstrong & Reay Developments Limited | Construction | 2024 |
| Armstrong 22 Ltd | Financial services | 2022 |
| Armstrong Business Solutions Ltd | Health & social care | 2024 |
| Armstrong Campbell Accountants LLP | | 2015 |
| Armstrong Campbell Limited Liability Partnership | | 2003 |
| Armstrong Energy Solutions Ltd | Professional & scientific | 2023 |
| Armstrong Media NE Ltd | Information & communication | 2026 |
| Armstrong Rail Ltd | Construction | 2023 |
| Armstrong, Addison & Company Limited | Professional & scientific | 1954 |
| Armstrongs Bricklaying Limited | Construction | 2019 |
| Armstrongs Effluent Disposal Limited | Water & waste | 2002 |
| ARN IT Solutions Limited | Professional & scientific | 2024 |
| Arne Limited | Administrative & support | 2026 |
| Arnside DP Ltd | Health & social care | 2025 |
| ARO Compliance Ltd | Professional & scientific | 2018 |
| ARO Wind Ltd | Construction | 2024 |
| Arofar Ltd | Manufacturing | 2023 |
| Aroma Global Gateway Ltd | Financial services | 2021 |
| Aroma Investments Limited | Real estate | 2013 |
| Aroma Ryton Ltd | Hospitality | 2024 |
| Aropama Ltd | Information & communication | 2013 |
| ARR Legal Services Limited | Professional & scientific | 2021 |
| ARR Property Management Ltd | Households | 2023 |
| Arrizel Consultancy Ltd | Administrative & support | 2020 |
| Arrocms Ltd | Information & communication | 2018 |
| Arrow Close Developments Ltd | Construction | 2020 |
| Arrow Comms Ltd | Information & communication | 2016 |
| Arrow Roofing Specialist NE Ltd | Construction | 2026 |
| Arrow Test Limited | Professional & scientific | 2024 |
| Arrows Corporation Limited | Other services | 2010 |
| ARS Auto Repair Ltd | Manufacturing | 2025 |
| Art for Arts Sake North East Ltd | Manufacturing | 2026 |
| Art Health Solutions Ltd | Other services | 2018 |
| Art of Stone (Newcastle) Limited | Construction | 2024 |
| Art Real Estate Management Ltd | Real estate | 2022 |
| Artdecor Ltd | Construction | 2025 |
| Artech Studios Limited | Professional & scientific | 2025 |
| Artemis Ventures Ltd | Professional & scientific | 2008 |
| Artful Dodgers Ltd | Professional & scientific | 2007 |
| Artguli Ltd | Arts & recreation | 2025 |
| Arthur Delivers Ltd | Transport & logistics | 2026 |
| Arthur Meadows Investment Ltd | Real estate | 2022 |
| Arthur Tremble (Holdings) Limited | Real estate | 1965 |
| Articulated Services Ltd | Transport & logistics | 2016 |
| Artin Sky Light Ltd | Construction | 2016 |
| Artis Consulting Limited | Professional & scientific | 2011 |
| Artisan Roofing Surrey Limited | Construction | 2008 |
| Artisan Treats Limited | Hospitality | 2024 |