| Alchem Process Ltd | Manufacturing | 2009 |
| Aledo Foods Ltd | Administrative & support | 2017 |
| Alex and Lucie Ltd | Hospitality | 2025 |
| ALEX2205 Ltd | Transport & logistics | 2026 |
| Alexander Financial Management Limited | Financial services | 2011 |
| Alexandra Accommodation Limited | Real estate | 2025 |
| ALF Group Holdings Ltd | Construction | 2022 |
| ALF Labs Ltd | Administrative & support | 2023 |
| Alfie's Coffee Company Ltd | Manufacturing | 2020 |
| Alfo Logistics Ltd | Transport & logistics | 2026 |
| Algar Travel Ltd | Transport & logistics | 2009 |
| ALI Dropshipping Ltd | Wholesale & retail | 2024 |
| Aliffe Properties Ltd | Real estate | 2024 |
| Aligned Training Solutions Ltd | Education | 2022 |
| ALL E Property Ltd | Real estate | 2025 |
| ALL Trades Plant Hire Ltd | Construction | 2024 |
| ALL Wales Sport Ltd | Arts & recreation | 2012 |
| Allcreations Limited | Manufacturing | 2025 |
| Allspark Electrical Services Limited | Construction | 2011 |
| Allure Investment Group Ltd | Real estate | 2024 |
| Alphabeast Ltd | Administrative & support | 2024 |
| ALS Consulting Services Limited | Professional & scientific | 2015 |
| ALS Property and Investment Ltd | Real estate | 2024 |
| Alvamlm Limited | Wholesale & retail | 2015 |
| Alyn Bowen Limited | Construction | 2022 |
| AM & JM Properties Ltd | Real estate | 2019 |
| Ambassador Windows and Home Improvements Limited | Manufacturing | 1985 |
| Amber Solutions Financial Planning LLP | | 2017 |
| Ambulance and Medical CPD Limited | Education | 2020 |
| Amelia Nail Bar Ltd | Other services | 2026 |
| Amelia Thorne Dance Company Ltd | Education | 2026 |
| AMG Industries PLC | Administrative & support | 1987 |
| AMG Resources Limited | Manufacturing | 1980 |
| Amigo Group Holdings Ltd | Financial services | 2025 |
| Amigo Leisure Services Ltd | Other services | 2025 |
| Amigos Event Management Ltd | Arts & recreation | 2024 |
| Amlind (UK) Limited | Arts & recreation | 1999 |
| Ammanford Self Storage Limited | Administrative & support | 2010 |
| AMP Media Development Ltd | Professional & scientific | 2013 |
| Amy's Foot Health Ltd | Other services | 2025 |
| Anbabil Ltd | Hospitality | 2024 |
| Andrew & Jemma Morgans Ltd | Transport & logistics | 2026 |
| Andrew Faulkner Associates Ltd | Professional & scientific | 2016 |
| Andrew M Williams Properties Limited | Households | 2018 |
| Andrew M Williams Wealth Management Ltd | Financial services | 2012 |
| Angels Domestic Services Limited | Administrative & support | 2011 |
| Anglepalm Limited | Financial services | 1994 |
| Animal Antics Limited | Agriculture & fishing | 2023 |
| Anthony Devonald Richards Limited | Professional & scientific | 2017 |
| Anthonyjames Catering Ltd | Hospitality | 2026 |
| Anturiaeth Limited | Wholesale & retail | 2013 |
| Anyone Waiting Ltd | Extraterritorial | 2021 |
| Aperture Automation Ltd. | Information & communication | 2011 |
| Apex Plastering and Building Ltd | Construction | 2019 |
| Apex Recycling and Waste Management Limited | Water & waste | 2025 |
| Apical Recruitment Ltd | Administrative & support | 2012 |
| Appliance Universe Ltd | Manufacturing | 2008 |
| ARA Lettings Ltd | Real estate | 2023 |
| ARB Holdings (South Wales) Limited | Financial services | 2024 |
| Arcadia Finance Ltd | Financial services | 2026 |
| Archbie Ltd | Construction | 2026 |
| Arhomeservices Ltd | Construction | 2023 |
| Arian Direct Ltd | Professional & scientific | 2015 |
| Arian Financial Planning Ltd | Financial services | 2011 |
| Arik Catering Limited | Hospitality | 2025 |
| Arnie Strong Ltd | Professional & scientific | 2026 |
| Art & Technology Contractors Ltd | Professional & scientific | 2015 |
| Arthur and ME Ltd | Wholesale & retail | 2024 |
| Arthurs Aerospace Consulting Ltd | Construction | 2012 |
| Asbo Fabrications Ltd | Manufacturing | 2021 |
| Ascot Aviation Ltd | Education | 2020 |
| Ashdown Kitchens Ltd | Wholesale & retail | 2000 |
| Ashley's Autos Limited | Administrative & support | 2000 |
| ASJ Europe Momentum Limited | Transport & logistics | 2024 |
| Asphalt & Bitumen Consulting Limited | Professional & scientific | 2012 |
| Aspire Mentoring Ltd | Education | 2023 |
| Aspire Timberframe & Construction Ltd | Manufacturing | 2019 |
| ASR Heating Group Limited | Construction | 2026 |
| ASR Projects Ltd | Construction | 2010 |
| ASR Property Developments Ltd | Real estate | 2018 |
| Astonlane Limited | Construction | 2000 |
| Astral Home Improvements Ltd | Construction | 2024 |
| Astro Building Services (Wales) Ltd | Construction | 2012 |
| Astro Home Lettings Limited | Real estate | 2026 |
| Ateb AI CYF | Information & communication | 2025 |
| Atlantic Driveways & Landscapes Ltd | Administrative & support | 2026 |
| Atlantis Acquisition Company Limited | Financial services | 2025 |
| Atlas Health and Wellbeing Limited | Health & social care | 2022 |
| ATM Tooling Wales Limited | Wholesale & retail | 2020 |
| Atoz Homes (Wales) Limited | Real estate | 2025 |
| Aubrey Construction Ltd | Construction | 2022 |
| Augusta Bay Holdings Ltd | Financial services | 2026 |
| Aurum Property Holdings Ltd | Real estate | 2025 |
| Aurum Wealth LLP | | 2017 |
| Automotive Lighting UK Limited | Manufacturing | 1998 |
| Autoshine Car Care Ltd | Administrative & support | 2019 |
| Autumn Properties Ltd | Real estate | 2021 |
| Avarina Connor Accountancy Ltd | Professional & scientific | 2013 |
| Avendesora Limited | Administrative & support | 2024 |
| Aviation Logistics Consultants Ltd | Professional & scientific | 2024 |