| Andrew Byrne Limited | Construction | 2017 |
| Aneurin House RTM Company Limited | Households | 2023 |
| Angel Chef Ltd | Hospitality | 2016 |
| Anglo Welsh Contracts Limited | Construction | 2018 |
| Anglo-Celtic Group Limited | Professional & scientific | 2004 |
| Anika Crane Fitness Ltd | Arts & recreation | 2022 |
| Anima Core Ltd | Information & communication | 2025 |
| Anneis Financial Advice Limited | Administrative & support | 2016 |
| Anodos Limited | Professional & scientific | 2014 |
| Anthony Management Limited | Professional & scientific | 2014 |
| Anubis Lock Shop Limited | Wholesale & retail | 2021 |
| Apex Litigation Services Ltd | Administrative & support | 2015 |
| Apex Refurbishment Ltd | Extraterritorial | 2023 |
| APM Pipe & Welding Solutions Limited | Professional & scientific | 2013 |
| Apprenticeship Group Wales Ltd | Education | 2018 |
| Aqua Dogs LLP | | 2006 |
| Aquagas Solutions Ltd | Financial services | 2025 |
| Aquagas Training UK Limited | Administrative & support | 2007 |
| Aqueduct Ltd | Information & communication | 2022 |
| AR Consulting Caerphilly Limited | Construction | 2022 |
| AR Digital Specialists Ltd | Professional & scientific | 2024 |
| AR Property Development Limited | Construction | 2019 |
| AR Securetech Ltd | Information & communication | 2025 |
| Arag Law Limited | Professional & scientific | 2005 |
| Arag Legal Expenses Insurance Company Limited | Financial services | 1909 |
| Arag PLC | Financial services | 1991 |
| Arag Services Limited | Administrative & support | 1997 |
| Arag UK Holdings Limited | Professional & scientific | 1997 |
| Arbil Properties Ltd | Extraterritorial | 2024 |
| ARC Contracting Ltd | Construction | 2012 |
| Arcanum Information Security Limited | Administrative & support | 2008 |
| Architectural and Structural Engineering Limited | Manufacturing | 2007 |
| Arco Construct Limited | Construction | 2026 |
| Arden Kitt Associates Limited | Professional & scientific | 2006 |
| ARK Health & Homecare Ltd | Health & social care | 2023 |
| Arkay Digital Limited | Information & communication | 2020 |
| Arms Park Financial Services Limited | Financial services | 1995 |
| Arpita DE Ltd | Extraterritorial | 2023 |
| Art Electrical Contractors Ltd | Construction | 2023 |
| Asbri Golf Ltd | Wholesale & retail | 2003 |
| Ascari Commercial Ltd | Households | 2025 |
| Ascari Office Limited | Administrative & support | 2015 |
| ASG Heating and Plumbing Limited | Construction | 2018 |
| Askfletch Limited | Professional & scientific | 2019 |
| Aspb Limited | Construction | 2004 |
| Aspect Installations UK Limited | Construction | 2008 |
| Asphalt Solutions Ltd | Professional & scientific | 2023 |
| Assisted Living Home Care Limited | Health & social care | 2022 |
| ASW Locum Services Ltd | Health & social care | 2025 |
| AT Jones Investments Limited | Real estate | 2025 |
| AT Welds Ltd | Manufacturing | 2024 |
| Ateb Groundworks Limited | Construction | 2024 |
| Atec Drainage Systems Limited | Water & waste | 2008 |
| Athena Properties and Management Ltd | Real estate | 2023 |
| Atmosphere Group Ltd | Manufacturing | 2026 |
| Atrium Property Management Ltd | Real estate | 2022 |
| Aura Headwear Ltd | Wholesale & retail | 2026 |
| Aureon Solar Ltd | Construction | 2026 |
| Aureza Ltd | Wholesale & retail | 2017 |
| Auto AKG Garage Ltd | Wholesale & retail | 2023 |
| Auto Locksmiths Association Limited | Extraterritorial | 2015 |
| Auto Training (Wales) Limited | Professional & scientific | 2019 |
| Auxillium Fitness Ltd | Arts & recreation | 2025 |
| Auxillium Property Holdings Ltd | Financial services | 2025 |
| AV8 Composite Ltd | Manufacturing | 2019 |
| Aviary (Caerphilly) Ltd | Hospitality | 2019 |
| Avkiran Company Ltd | Wholesale & retail | 2020 |
| AW Cricket Coaching Ltd | Arts & recreation | 2022 |
| Awen Collective Limited | Information & communication | 2017 |
| AWK Site Services Ltd | Construction | 2025 |
| AWS Signature Factory Limited | Hospitality | 2025 |
| Axyomagency Ltd | Professional & scientific | 2026 |
| AY Property Development Limited | Construction | 2024 |
| Ayjay Group Ltd | Construction | 1996 |
| AZM Medical Solutions UK Ltd | Health & social care | 2019 |
| Aztec Aero Engines LT Ltd | Professional & scientific | 2024 |
| Aztec Sails and Covers Ltd | Manufacturing | 2021 |
| Aûtentic Autism Consultancy and Training Ltd | Education | 2024 |
| B&B Property Developers Finance Ltd | Construction | 2022 |
| B&B Property Developers Ltd | Financial services | 2019 |
| B&B Property Developers Management Limited | Construction | 2022 |
| B&B Property Developers Projects Limited | Construction | 2022 |
| B&C Catering Ltd | Hospitality | 2024 |
| B&F Investments Ltd | Real estate | 2025 |
| B&M Brickwork Ltd | Information & communication | 2017 |
| B-Spoke Interiors Ltd | Wholesale & retail | 2023 |
| B.B Groundworks and Property Renovation Limited | Households | 2025 |
| B.L. Rigging Ltd | Construction | 2022 |
| Babhaus Limited | Hospitality | 2020 |
| Bahoz Car Valeting Limited | Administrative & support | 2025 |
| Bailey Elevator Services Limited | Manufacturing | 2010 |
| Bailey Hire Limited | Construction | 1983 |
| Baka Car Care Ltd | Other services | 2019 |
| Baldilocks Ltd | Wholesale & retail | 2024 |
| Ball Grab and Tipper Service Ltd | Transport & logistics | 2026 |
| Baracus Safety Ltd | Wholesale & retail | 2024 |
| Barnes & Racine Engineering Ltd | Manufacturing | 2024 |
| Barod Property Services Ltd | Administrative & support | 2023 |
| Barry Bros Ltd | Wholesale & retail | 2024 |
| Barryboy Limited | Construction | 2016 |