| Alex French Associates Limited | Professional & scientific | 2010 |
| Alexander Constructors Ltd | Construction | 2023 |
| Alexander Home Builders Limited | Real estate | 2007 |
| Alexandra Bay Management Company Limited | Households | 2007 |
| Alexandra Court (Penarth) Management Company Limited | Households | 1989 |
| Alexandra House Limited | Real estate | 2014 |
| Alida Cosmetics Limited | Other services | 2014 |
| Alida Laser Limited | Other services | 2021 |
| Alison Watkins Communications Limited | Professional & scientific | 2015 |
| Allens Printers Holdings Limited | Administrative & support | 2008 |
| Allens Printers Limited | Manufacturing | 1966 |
| Almost Enjoyable Ltd | Manufacturing | 2019 |
| Alternate Software Limited | Information & communication | 2026 |
| Alternative Learning System Academy Ltd | Education | 2024 |
| Altitude Engineering Europe Ltd | Information & communication | 2019 |
| Altitude Scaffold Ltd | Construction | 2020 |
| Altitude Scaffolding Solutions Ltd | Construction | 2018 |
| Alys Carlton Consulting Limited | Professional & scientific | 2020 |
| Alyson Macdonald Human Resources Limited | Administrative & support | 2014 |
| Amazing Beds Limited | Wholesale & retail | 2018 |
| Amor Cleaning Services Ltd | Administrative & support | 2025 |
| Amore Hair Boutique Limited | Other services | 2023 |
| Amore Property Limited | Real estate | 2022 |
| Amoretto Design Limited | Construction | 2004 |
| Amplify Training and Events Ltd | Administrative & support | 2022 |
| Amro Properties Ltd | Construction | 2021 |
| Amser Investments Limited | Wholesale & retail | 2023 |
| AMY Guppy Academy Ltd | Arts & recreation | 2026 |
| AMZ Medical Ltd | Health & social care | 2021 |
| Andrew Michael Pemberton Group Limited | Professional & scientific | 2022 |
| Anker & Marsh Ltd | Professional & scientific | 2018 |
| Antonesei Ltd | Transport & logistics | 2025 |
| APE Ranch Ltd | Agriculture & fishing | 2025 |
| APOTHECARY64 Limited | Manufacturing | 2020 |
| Aptitude Consult Ltd | Education | 2018 |
| Aquarius Promotions Limited | | 1989 |
| Arcade Hospitality Cardiff Limited | Real estate | 2020 |
| Archaeological Sciences Limited | Professional & scientific | 2018 |
| Arche Innovations Limited | Financial services | 2012 |
| Arcudio Limited | Professional & scientific | 2019 |
| Aristople Limited | Professional & scientific | 2019 |
| Arnold Building and Carpentry Limited | Construction | 2007 |
| Art Acumen Ltd | Administrative & support | 2009 |
| Arth Strength Ltd | Arts & recreation | 2025 |
| Artisan Nails Ltd | Other services | 2025 |
| Ascendance Theatre Arts Ltd. | Arts & recreation | 2011 |
| ASG Plumbing & Heating Services Ltd | Construction | 2025 |
| Ashi and Akku Properties Ltd | Real estate | 2020 |
| Ashley James Automotive Limited | Wholesale & retail | 2019 |
| ASI Developments Limited | Construction | 2014 |
| Aspire Homes Holding Ltd | Real estate | 2025 |
| Aspire Homes Property Group Ltd | Real estate | 2023 |
| Associated Smoke & Fire Products Limited | Manufacturing | 2023 |
| Assured Construction and Compliance Consultants Ltd | Construction | 2019 |
| Astronaut Leadership Limited | Education | 2014 |
| AT Project Services Limited | Professional & scientific | 2018 |
| Atfq Advisory Ltd | Information & communication | 2026 |
| Atlas Homes & Property Maintenance Limited | Construction | 2019 |
| Atlas Property Developments Ltd | Construction | 2017 |
| Autospray Cardiff Ltd | Wholesale & retail | 2012 |
| Avabelle Limited | Public administration | 2018 |
| Avant Wine Ltd | Wholesale & retail | 2022 |
| AVE Project Management Ltd | Professional & scientific | 2025 |
| AW Management Ltd | Professional & scientific | 2019 |
| Aware Breathwork Ltd | Information & communication | 2024 |
| Axiom Forge (LD1) Limited | Information & communication | 2026 |
| Axiom Forge Limited | Information & communication | 2026 |
| Axis Roofing Limited | Construction | 2019 |
| Ayan World Music CIC | Education | 2017 |
| Azure Science Ltd | Professional & scientific | 2026 |
| B'S Trees & Hedges Ltd | Administrative & support | 2021 |
| B-Active Services Limited | Other services | 2020 |
| Baabaa Ltd | Wholesale & retail | 2021 |
| Baby Bare Bubbles Limited | Wholesale & retail | 2018 |
| Badmonkey Ltd | Information & communication | 2023 |
| BAGUETTES2GO Ltd | Hospitality | 2024 |
| Bakelite Synthetics UK Limited | Manufacturing | 1965 |
| Bakelite UK Holding Ltd. | Financial services | 2020 |
| Bakelite UK Intermediate Ltd. | Financial services | 2020 |
| Bakelite UK Topco Ltd. | Financial services | 2020 |
| Baker Lewis Properties Ltd | Real estate | 2021 |
| Balmoral Quays Management (Penarth) Ltd | Real estate | 2013 |
| Barber Blades Ltd | Wholesale & retail | 2010 |
| Barber-Rossa Limited | Other services | 2019 |
| Barbershop Llandaff Ltd | Other services | 2023 |
| Barker Deli Ltd | Wholesale & retail | 2025 |
| Barry Industrial Services Ltd. | Professional & scientific | 1998 |
| Barry Training Services Limited | Education | 1990 |
| Bassline Acoustics Ltd | Professional & scientific | 2022 |
| Bay Accountancy Limited | Professional & scientific | 2006 |
| Bay Information Systems Limited | Information & communication | 2013 |
| Bayland Estates Ltd | Real estate | 2017 |
| Bayliss Health Ltd | Health & social care | 2022 |
| BB Propco Limited | Construction | 2023 |
| BCC DLG (UK) Ltd | Professional & scientific | 2023 |
| BDM (South Wales) Limited | Hospitality | 2020 |
| BE Beautiful by SUE Ltd | Administrative & support | 2007 |
| BE Claims Ready Limited | Administrative & support | 2018 |
| Beachcliff Management Company Limited | Administrative & support | 2016 |
| Beacon Events Ltd. | Professional & scientific | 2016 |