| ARK IG Management Ltd | Administrative & support | 2025 |
| Arkadata Ltd | Other services | 2021 |
| Arkas Enterprises Limited | Professional & scientific | 2016 |
| Arkeera Limited | Other services | 2025 |
| Arkenz Ltd | Wholesale & retail | 2020 |
| Arkke Capital Ltd | Financial services | 2020 |
| Arkona PC | | 2017 |
| Arkoosa Services Ltd | Wholesale & retail | 2021 |
| Arková Ltd | Other services | 2025 |
| Arks Transport Limited | Transport & logistics | 2020 |
| Arkwright and Co Limited | Extraterritorial | 1991 |
| ARL Ling Limited | Wholesale & retail | 2025 |
| Arlo & Ball Limited | Professional & scientific | 2024 |
| Arlwick Warrick Ltd | Wholesale & retail | 2026 |
| ARM Associates & Consultancy Limited | Other services | 2014 |
| ARM Commercial Services Limited | Construction | 2016 |
| Arma Online Marketing Ltd. | Wholesale & retail | 2014 |
| Armada Tech Solutions Ltd | Information & communication | 2023 |
| Armadillo Support Limited | Professional & scientific | 2019 |
| Arman Naji Creative Limited | Professional & scientific | 2025 |
| Arman Vape Ltd | Wholesale & retail | 2025 |
| Armanton Trading LP | | 2017 |
| Armash Ltd | Real estate | 2017 |
| Armcare Ltd | Health & social care | 2019 |
| Armforce Global Limited | Administrative & support | 2020 |
| Armorvelmora Ltd | Wholesale & retail | 2026 |
| Armour Security Solutions Ltd | Wholesale & retail | 2019 |
| Armourgrip Ltd | Wholesale & retail | 2020 |
| Armstrong Peters Ltd | Real estate | 2025 |
| Arno Commercial Solutions Ltd | Financial services | 2023 |
| Arnold Richer, Curran Limited | Financial services | 1974 |
| Arnos Chicken Time Ltd | Hospitality | 2015 |
| ARO Properties (NE) Limited | Construction | 2025 |
| Arobella Holding Ltd | Professional & scientific | 2024 |
| Arolita Limited | Administrative & support | 2016 |
| Aroma Holistic Health & Beauty Limited | Wholesale & retail | 2007 |
| Aromaco Limited | Wholesale & retail | 2018 |
| Aromada Limited | Manufacturing | 2019 |
| Aromas Fragrance UK Ltd | Wholesale & retail | 2025 |
| Aronic Limited | Wholesale & retail | 2019 |
| Aroosamunir Trading Limited | Wholesale & retail | 2025 |
| Arotrax Solutions Limited | Information & communication | 2025 |
| Arox Plus Ltd | Wholesale & retail | 2026 |
| Aroxco Limited | Wholesale & retail | 2025 |
| ARP Cash and Carry Ltd | Wholesale & retail | 2025 |
| ARP Locum Services Limited | Health & social care | 2015 |
| Arpad Construction Limited | Construction | 2022 |
| Arpitha Pereira Ltd | Health & social care | 2026 |
| Arqentra Limited | Information & communication | 2026 |
| Arquitectos Grupo Baleares Ltd | Administrative & support | 2014 |
| Arrah Homes Limited | Real estate | 2019 |
| Arrayhan Property Ltd | Financial services | 2025 |
| Arrel Marketing Ltd | Professional & scientific | 2026 |
| Arrex Consulting Limited | Information & communication | 2014 |
| Arriel Solutions Limited | Administrative & support | 2015 |
| Arrival Store Limited | Wholesale & retail | 2024 |
| Arrow Fortune Limited | Financial services | 2024 |
| Arrowhill Solutions Limited | Extraterritorial | 2024 |
| ARS Cardiff Limited | Hospitality | 2016 |
| ARS Technology Limited | Information & communication | 2025 |
| ARS Trading and Contracting Ltd | Wholesale & retail | 2025 |
| Arsa Cardiff Ltd | Real estate | 2024 |
| Arsalaan Mahmood Ltd | Agriculture & fishing | 2019 |
| Arshad Muhammad Ltd | Wholesale & retail | 2022 |
| Arslan ALI Group Ltd | Wholesale & retail | 2025 |
| Arslan Rajpoot Ltd | Wholesale & retail | 2025 |
| Arslan Supermart Ltd | Wholesale & retail | 2025 |
| Art & Literature Ltd | Information & communication | 2003 |
| Art Apparel Limited | Wholesale & retail | 2010 |
| Art Don'T PAY Ltd | Arts & recreation | 2020 |
| Art for Screen, Scenery and Creative Health Ltd | Arts & recreation | 2025 |
| Art for the People Limited | Wholesale & retail | 2017 |
| Art Market Cardiff Ltd | Wholesale & retail | 2023 |
| Art of Defence Limited | Arts & recreation | 2013 |
| Art of Teams Ltd | Professional & scientific | 2020 |
| Art of Travel Enterprises Ltd | Financial services | 2025 |
| Art of Travel Group Ltd | Administrative & support | 2023 |
| Art Specialist Travel Limited | Administrative & support | 2019 |
| Art Travel Group Limited | Extraterritorial | 2011 |
| ART360 Studio CIC | Professional & scientific | 2021 |
| Artanz Solutions & Services Ltd | Transport & logistics | 2025 |
| Artcor Limited | Arts & recreation | 2017 |
| Arte Hospitality Ltd | Wholesale & retail | 2025 |
| Artecon Europe B.V. | | 1996 |
| Artekya Ltd | Wholesale & retail | 2023 |
| Artemia Ltd | Information & communication | 2025 |
| Artemis FMC Limited | Administrative & support | 2013 |
| Artemis Global Art Limited | Arts & recreation | 2015 |
| Artes Mundi Prize Limited | Arts & recreation | 2001 |
| Artesiano PC | | 2017 |
| Arteus (UK) Holding Limited | Administrative & support | 1993 |
| Artevi Films Ltd. | Arts & recreation | 2016 |
| Artha Real Estate Ltd | Real estate | 2025 |
| Artheon Trade Ltd | Wholesale & retail | 2025 |
| Arthole CIC | Wholesale & retail | 2022 |
| Arthouse Manco Limited | Real estate | 2011 |
| Arthroprime Ltd | Health & social care | 2026 |
| Arthur & Hamilton Limited | Real estate | 2022 |
| Arthur Marketing Limited | Information & communication | 2013 |
| Arthurs by Arthur Ltd | Hospitality | 2024 |