| Aqua Academy Ltd | Arts & recreation | 2002 |
| Aqua Farms Limited | Agriculture & fishing | 2017 |
| Aqua Passport Limited | Arts & recreation | 2013 |
| Aqua Revival Bathrooms Ltd | Construction | 2025 |
| Aqua Swansea Ltd | Arts & recreation | 2019 |
| Aquagas Plumbing & Heating Services Limited | Construction | 2016 |
| Aquarius Land Ltd | Construction | 2001 |
| Aquarius Plumbing Solutions Limited | Construction | 2018 |
| Aquaserve Plumbing & Heating Ltd | Construction | 2021 |
| Aquasol Water Systems Ltd | Construction | 2017 |
| Aquatic Specialist Services Ltd | Agriculture & fishing | 2016 |
| Aquatic Specialist Wimborne Limited | Agriculture & fishing | 2024 |
| Aquatic Supplies and Services Wales Ltd | Agriculture & fishing | 2014 |
| AR Common UK Limited | Manufacturing | 2018 |
| AR Plumbing, Heating & GAS Ltd | Construction | 2021 |
| Aragan Sports Ltd. | Arts & recreation | 2012 |
| Aram Investments Limited | Real estate | 2015 |
| Arborum Limited | Agriculture & fishing | 2008 |
| Arbourne's Country Kitchen Limited | Manufacturing | 2014 |
| ARC Building & Home Improvements Ltd | Construction | 2025 |
| ARC Hospitality Ltd | Hospitality | 2018 |
| Arcadia Cosmetics Limited | Professional & scientific | 2013 |
| Arcadia Medical Limited | Professional & scientific | 2013 |
| Arcadia Pharma Limited | Manufacturing | 2013 |
| Arcadia Pharmaceuticals Limited | Professional & scientific | 2013 |
| Arcadia Specials Limited | Professional & scientific | 2013 |
| Arcari Property Ltd | Real estate | 2025 |
| Arcform Software Limited | Information & communication | 2026 |
| Arch Equip Ltd | Information & communication | 2021 |
| Archaeological Research Limited | Information & communication | 2007 |
| Archdruid Ltd | Wholesale & retail | 2020 |
| Archfin Limited | Real estate | 2021 |
| Archibald & Millicent Properties LLP | | 2020 |
| Architech Consulting Limited | Information & communication | 2023 |
| Architectural Cleaning Services Limited | Construction | 2010 |
| Architectural Design Services (Swansea) Limited | Professional & scientific | 2017 |
| Arcsafe Ltd | Construction | 2019 |
| Arctec Fabrication Limited | Professional & scientific | 2017 |
| Ardius Limited | Administrative & support | 2017 |
| ARE Purchasing Solutions Ltd | Extraterritorial | 2018 |
| ARE Wealth Management Ltd | Professional & scientific | 2018 |
| Arenaco Ltd | Real estate | 2016 |
| Ares Fight Gear Limited | Wholesale & retail | 2024 |
| Aresals Limited | Professional & scientific | 2025 |
| Arete AI App Ltd | Information & communication | 2025 |
| Argentus Consulting Limited | Professional & scientific | 2023 |
| Argip Technologies Limited | Professional & scientific | 2014 |
| Argutus Legal Ltd | Professional & scientific | 2021 |
| ARI Software Ltd | Construction | 2021 |
| Arian Barber (Winch WEN) Ltd | Other services | 2022 |
| Ariana Ichim Ltd | Transport & logistics | 2025 |
| Ariel Finance Limited | Financial services | 1982 |
| Aries Services Wales Ltd | Other services | 2016 |
| Aries Stairlifts Ltd | Wholesale & retail | 2015 |
| Arinco Services Limited | Professional & scientific | 1983 |
| Ariyah's Dining & Functions Ltd | Hospitality | 2024 |
| Arize Properties Ltd | Real estate | 2024 |
| ARK Appliances Limited | Other services | 2003 |
| ARK Electronics UK Ltd | Wholesale & retail | 2015 |
| ARK Sale Group Limited | Wholesale & retail | 2026 |
| ARK Sentinel Ltd | Administrative & support | 2025 |
| Arkay Timber Products Limited | Manufacturing | 2021 |
| ARM Investors Ltd | Construction | 2019 |
| Armine Garages Limited | Wholesale & retail | 1962 |
| Armstrong & Flint Limited | Professional & scientific | 2020 |
| Armstrong Health and Wellness Limited | Other services | 2017 |
| Arnold and Spark Limited | Real estate | 1974 |
| ARO Developments Ltd | Real estate | 2020 |
| Aroma Services Ltd | Real estate | 2025 |
| Arora Stores Ltd | Wholesale & retail | 2017 |
| Aros Management Ltd | Professional & scientific | 2024 |
| Aros W2 Ltd | Real estate | 2024 |
| Aroundinteger Ltd | Information & communication | 2025 |
| Arsak Ltd | Wholesale & retail | 2020 |
| Art Deco Emporium Ltd. | Wholesale & retail | 2015 |
| Art Swansea CIC | Arts & recreation | 2024 |
| Artemis Womens Health Ltd | Health & social care | 2025 |
| Artenovas Limited | Wholesale & retail | 2024 |
| Artform Recordings Ltd | Information & communication | 2024 |
| Arthur Lawrence UK Ltd | Administrative & support | 2012 |
| Arthur Llewellyn Jenkins | Wholesale & retail | 2015 |
| Arthur Llewellyn Property Ltd | Real estate | 2023 |
| Arthur Neave Ltd | Hospitality | 2016 |
| Arthur Reginald Construction Limited | Construction | 2023 |
| Arthur Reginald Convenience Store Limited | Wholesale & retail | 2023 |
| Arthur's Stone Brewery Ltd | Manufacturing | 2020 |
| Artisan Business Services Ltd | Extraterritorial | 2001 |
| Artisan Contractors Ltd | Construction | 2021 |
| Artisan Flooring Limited | Construction | 2005 |
| Artisan Home & Property Solutions Ltd | Construction | 2025 |
| Artisan Stone Supplies Limited | Administrative & support | 2006 |
| Artstraws Limited | Manufacturing | 1983 |
| Artsy Beaver Co Ltd | Wholesale & retail | 2024 |
| Artyco Ltd | Information & communication | 2024 |
| Aruloan Ltd | Wholesale & retail | 2023 |
| Arva Investments Limited | Real estate | 2014 |
| Arvo Digital Ltd | Information & communication | 2024 |
| Arwain Limited | Professional & scientific | 2021 |
| Arwel's Hairdressers Limited | Other services | 2025 |
| Aryaancompany Ltd | Other services | 2023 |