| Aurum Tech Minerals Holding Ltd | Mining & quarrying | 2024 |
| Auryne Ltd | Education | 2025 |
| Ausjojo Ltd | Wholesale & retail | 2025 |
| Austexx Limited | Other services | 2020 |
| Austin Partnership Employee Ownership Trustee Limited | Professional & scientific | 2022 |
| Austin Partnership Limited | Construction | 1987 |
| Austindent Limited | Health & social care | 2022 |
| Austral Blue Ltd | Information & communication | 2025 |
| Australia Bondunte Biotechnology Co., Ltd | Mining & quarrying | 2026 |
| Australia Road Management Company Limited | Real estate | 1991 |
| Authentic Spice Grays Limited | Hospitality | 2026 |
| Authentic Thai Massage & Spa Limited | Other services | 2024 |
| Authentic World Limited | Information & communication | 2004 |
| Authenticbrandbag Ltd | Manufacturing | 2025 |
| Authorised Limited | Manufacturing | 2019 |
| Autism Ally Ltd | Other services | 2023 |
| Autism in Motorsports (AIM) | Arts & recreation | 2020 |
| Autism Spectrum Connections Cymru | Health & social care | 2013 |
| Autistic Minds Limited | Information & communication | 2010 |
| Autmm Technologies Ltd | Wholesale & retail | 2025 |
| Auto AD Ltd | Wholesale & retail | 2023 |
| Auto Care Plus Limited | Wholesale & retail | 2019 |
| Auto Centre Tyre Ltd | Wholesale & retail | 2026 |
| Auto Claim AI Ltd | Information & communication | 2025 |
| Auto Consultancy Ltd | Professional & scientific | 2020 |
| Auto Diagnostic Deals Limited | Wholesale & retail | 2016 |
| Auto Drive Cardiff Ltd | Wholesale & retail | 2025 |
| Auto E-Commerce Limited | Information & communication | 2010 |
| Auto Essence Ltd | Wholesale & retail | 2016 |
| Auto Executive Cars Limited | Transport & logistics | 2017 |
| Auto Kings Tuning Ltd | Wholesale & retail | 2019 |
| Auto Lane Limited | Wholesale & retail | 2026 |
| Auto Ledger Sytems Ltd | Information & communication | 2021 |
| Auto Pars (Cardiff) Ltd | Wholesale & retail | 2024 |
| Auto Parts Nation Ltd | Wholesale & retail | 2024 |
| Auto Range Trade Centre Group Ltd | Wholesale & retail | 2026 |
| Auto Sensors Ltd | Wholesale & retail | 2011 |
| Auto Sourcing Ltd | Wholesale & retail | 2024 |
| Auto Sweets Ltd | Wholesale & retail | 2025 |
| Auto Trade Smart Ltd | Information & communication | 2018 |
| Auto Vanguard Direct Limited | Wholesale & retail | 2017 |
| Auto Windscreens Limited | Transport & logistics | 1971 |
| Autoadx Ltd | Professional & scientific | 2025 |
| AUTOASSIST247 Recovery Ltd | Wholesale & retail | 2019 |
| Autocad & Revit 3D Drafting Ltd | Professional & scientific | 2018 |
| Autocadence AI Ltd | Professional & scientific | 2026 |
| Autocart Limited | Real estate | 1976 |
| Autocore Technology Co., Ltd. | Information & communication | 2020 |
| Autocraft Cardiff Limited | Wholesale & retail | 2003 |
| Autodice Ltd | Manufacturing | 2016 |
| Autodragonrepairs Ltd | Wholesale & retail | 2024 |
| Autodragons Limited | Wholesale & retail | 2024 |
| Autoexportuk Ltd | Wholesale & retail | 2025 |
| Autogem Logistics Ltd | Transport & logistics | 2020 |
| Autogem Ltd | Administrative & support | 2018 |
| Autohouse Cardiff Limited | Other services | 2016 |
| Autolec Cctv Limited | Wholesale & retail | 2019 |
| Automan Motors Limited | Wholesale & retail | 2019 |
| Automango Ltd | Information & communication | 2019 |
| Automarx Limited | Manufacturing | 2014 |
| Automates Limited | Wholesale & retail | 2025 |
| Automations AI Limited | Information & communication | 2023 |
| Automingle Limited | Wholesale & retail | 2026 |
| Automotics Limited | Professional & scientific | 2015 |
| Automotive Car Wash Ltd | Other services | 2020 |
| Automotive Cardiff Ltd | Wholesale & retail | 2016 |
| Automotive Consultants Limited | Wholesale & retail | 2020 |
| Automotive Distribution Ltd | Transport & logistics | 2019 |
| Automotive Majic Goods and Services Ltd | Wholesale & retail | 2016 |
| Automotive Mediation Limited | Other services | 2018 |
| Automotive Programming Services Limited | Information & communication | 2025 |
| Autonomous Land & Property Investments Limited | Real estate | 2018 |
| Autonomous Mergers and Acquisitions Ltd | Professional & scientific | 2018 |
| Autonomy Development Ltd | Professional & scientific | 2018 |
| Autonomy Property Limited | Construction | 2003 |
| Autopia Mobile Tech Ltd | Wholesale & retail | 2025 |
| Autopoint (Pontyclun) Limited | Real estate | 1960 |
| Autosounds Limited | Manufacturing | 2004 |
| Autowise Vehicle Services Limited | Wholesale & retail | 2011 |
| Autoworx Recovery Limited | Wholesale & retail | 2014 |
| Autumn Crossborder Co Limited | Wholesale & retail | 2025 |
| Autumn Leaf Creations Ltd | Wholesale & retail | 2025 |
| Autumngram Ltd | Wholesale & retail | 2024 |
| Autumns Corner Ltd | Manufacturing | 2021 |
| Auventtech Ltd | Manufacturing | 2023 |
| Auviva Ltd | Wholesale & retail | 2025 |
| Auxano International Limited | Transport & logistics | 2025 |
| Auxilium International Ltd | Professional & scientific | 2018 |
| Auxland Ltd | Construction | 2020 |
| AV Cardiff Ltd | Wholesale & retail | 2026 |
| AV Dispatchers Limited | Transport & logistics | 2025 |
| AV Equity Trading Limited | Financial services | 2012 |
| AV Impex Group Ltd | Transport & logistics | 2020 |
| AV Learning Health Care Ltd | Information & communication | 2023 |
| AV Sales Agency Ltd | Wholesale & retail | 2019 |
| AV Scientific & Construction Ltd | Professional & scientific | 2018 |
| AV Service Solutions Ltd | Administrative & support | 2019 |
| AV Smart Party Planners Ltd | Administrative & support | 2021 |
| AV Tech Install Ltd | Construction | 2017 |
| AVA (Rd&D) C.I.C. | Arts & recreation | 2022 |