| Atkins Infotech Limited | Information & communication | 2019 |
| Atkinson Broking Solutions Limited | Financial services | 2014 |
| Atkinson Electrical Limited | Construction | 2016 |
| Atkinson Solicitors Limited | Professional & scientific | 2013 |
| Atlantic Beauty Store Limited | Wholesale & retail | 2014 |
| Atlantic Energies Ltd | Manufacturing | 2025 |
| Atlantic Holdco Limited | Professional & scientific | 2019 |
| Atlantic Home Solution Ltd | Construction | 2024 |
| Atlantic Offerco Limited | Professional & scientific | 2019 |
| Atlantic Support Limited | Health & social care | 2017 |
| Atlantica Group Ltd | Hospitality | 2022 |
| Atlas Group Travel Limited | Administrative & support | 2006 |
| Atlas Prop 1 Ltd | Real estate | 2023 |
| Atlas Prop 2 Limited | Real estate | 2024 |
| Atlas Prop 3 Ltd | Real estate | 2024 |
| Atlas Surveys LLP | | 2008 |
| Atlasworx Ltd | Manufacturing | 2025 |
| Atprovision Ltd | Information & communication | 2025 |
| Attribute Sports Development Ltd | Education | 2005 |
| AU2MATE Ltd | Information & communication | 2011 |
| Audio-Tek Shropshire Limited | Hospitality | 2025 |
| Audley House Mews RTM Company Ltd | Households | 2013 |
| Audosta Ltd | Water & waste | 2009 |
| Audosta Recycling Ltd | Wholesale & retail | 2024 |
| Augustus Industries Ltd | Financial services | 2025 |
| Aunzton Ltd | Extraterritorial | 2014 |
| Aura Newport Ltd | Other services | 2026 |
| Auradome UK Ltd | Arts & recreation | 2019 |
| Aurama Limited | Professional & scientific | 2025 |
| Auray Intelligence Ltd | Information & communication | 2024 |
| Aureus Management Ltd | Professional & scientific | 2023 |
| Aurora Capital Ltd | Extraterritorial | 2022 |
| Aurora Creative Limited | Information & communication | 2017 |
| Aurora Global Capital Ltd | Extraterritorial | 2022 |
| Aurora Gray Ltd | Other services | 2019 |
| Aurovia Ltd | Professional & scientific | 2025 |
| Authentic Spicy Cuisine Ltd | Hospitality | 2023 |
| Auto Aspire Ltd | Wholesale & retail | 2020 |
| Auto Direct Ltd | Wholesale & retail | 2024 |
| Auto Electro Pawel MB Ltd | Wholesale & retail | 2025 |
| Auto FIX Newport Ltd | Wholesale & retail | 2025 |
| Auto Phoenix Ltd | Wholesale & retail | 2020 |
| Auto Reespect Ltd | Wholesale & retail | 2018 |
| Auto Smarts Repair Ltd | Wholesale & retail | 2025 |
| Auto Solutions Newport Ltd | Wholesale & retail | 2024 |
| Auto Unit Ltd | Wholesale & retail | 2018 |
| Auto Venue Ltd | Wholesale & retail | 2022 |
| Auto-Keys of Shropshire Ltd | Other services | 2024 |
| Auto-Lites Limited | Wholesale & retail | 2006 |
| Autoaccess Ltd | Wholesale & retail | 2025 |
| Autogem Motors Ltd | Wholesale & retail | 2025 |
| Autohaus Newport LLP | | 2017 |
| Autolinks Brynmawr Limited | Wholesale & retail | 2019 |
| Automania (South Wales) Limited | Wholesale & retail | 2009 |
| Automatavault Ltd | Information & communication | 2026 |
| Automated Welding Solutions Ltd | Professional & scientific | 2026 |
| Automatic Doors and Entrance Solutions Limited | Construction | 2018 |
| Automotive Components (Salop) Limited | Wholesale & retail | 1978 |
| Automotive Intelligence Solutions Ltd | Wholesale & retail | 2023 |
| Autonomous Marine Limited | Extraterritorial | 2024 |
| Autopoint Newport Ltd | Wholesale & retail | 2024 |
| Autoway Service Ltd | Wholesale & retail | 2024 |
| Auximat Ltd | Administrative & support | 2013 |
| AV Facade Services Ltd | Construction | 2018 |
| AV Watts Ltd | Other services | 2022 |
| Avaa Gasrad Limited | Health & social care | 2016 |
| Avabrook Developments Limited | Construction | 2025 |
| Avalon House International Limited | Real estate | 1995 |
| Avanz Ltd | Wholesale & retail | 2026 |
| Avdg Properties Limited | Real estate | 2025 |
| Aventa Advisory Limited | Information & communication | 2026 |
| Aventador Estates Limited | Construction | 2011 |
| Aventis Health Ltd | Health & social care | 2026 |
| Avery Management Consulting Limited | Professional & scientific | 2023 |
| Avian Odyssey Ltd | Administrative & support | 2025 |
| Aviation Lease Works Limited | Administrative & support | 2026 |
| Avidius Ltd | Real estate | 2026 |
| Avion Designs Limited | Transport & logistics | 1993 |
| Avondale UK Event & Conference Limited | Extraterritorial | 2014 |
| AW Accountancy Services Limited | Professional & scientific | 2019 |
| AW Developments Exports Ltd | Wholesale & retail | 2009 |
| AW Electrical Solutions Ltd | Construction | 2025 |
| AW Preservations Ltd | Construction | 2023 |
| Awat.A Limited | Hospitality | 2013 |
| Awattz Limited | Professional & scientific | 2024 |
| Awdev Ltd | Wholesale & retail | 2020 |
| AWE Properties Ltd | Real estate | 2025 |
| Awesome Pawsome Pet Supplies Ltd | Wholesale & retail | 2023 |
| AWH Express Sport Limited | Households | 2011 |
| Axiom IT Limited | Financial services | 2023 |
| Axiom Lifting Solutions Limited | Manufacturing | 2015 |
| Axiom Manufacturing Services Ltd. | Manufacturing | 1997 |
| Axiom MS Limited | Real estate | 2008 |
| Axios Investments Limited | Construction | 2016 |
| Axis Adventures Ltd | Arts & recreation | 2026 |
| Axis Consult Ltd | Administrative & support | 2026 |
| Axles Truck and Trailer Limited | Wholesale & retail | 2013 |
| Axonordic Ltd | Wholesale & retail | 2021 |
| Axylhomes Ltd | Financial services | 2020 |
| AY Capital Ltd | Wholesale & retail | 2026 |