| (THE) Jersey HUT UK Ltd | Wholesale & retail | 2022 |
| 1 Tan-Y-Bryn Street Limited | Real estate | 2009 |
| 3DE BIM Ltd | Construction | 2021 |
| 3G Consultancy & Training Ltd | Professional & scientific | 2014 |
| 3S Convenience Store Ltd | Wholesale & retail | 2016 |
| A & C Enterprises Limited | Real estate | 2019 |
| A B Geological Limited | Mining & quarrying | 2001 |
| A Class Bifolding Doors & Windows Ltd | Extraterritorial | 2020 |
| A F G Engineering Limited | Extraterritorial | 2012 |
| A LEA (Jewellers) Limited | Wholesale & retail | 2002 |
| A N Retailers Ltd | Wholesale & retail | 2024 |
| A Stubbs Limited | Administrative & support | 2007 |
| A. T. Railway Services Limited | Construction | 2012 |
| A1 Homes Limited | Real estate | 2017 |
| A1 Motoring Driving School Ltd | Transport & logistics | 2017 |
| A1 Training and Testing Ltd | Other services | 2015 |
| A2B Taxis Aberdare Ltd | Transport & logistics | 2025 |
| Aacg Aberdare Limited | Construction | 2003 |
| Aadhan Limited | Real estate | 2018 |
| Aber Property Ltd | Financial services | 2025 |
| Aberaman Chippy Ltd | Hospitality | 2024 |
| Aberaman P.O. Limited | Transport & logistics | 2026 |
| Aberdare Accountancy Services Limited | Professional & scientific | 2019 |
| Aberdare Auto Trade Limited | Wholesale & retail | 2015 |
| Aberdare Automotive Services Ltd | Wholesale & retail | 2025 |
| Aberdare Construction Limited | Construction | 1997 |
| Aberdare Cottage Company,Limited(The) | Real estate | 1909 |
| Aberdare Crash Accident Repair Centre Ltd | Wholesale & retail | 2017 |
| Aberdare Demolition Limited | Construction | 1991 |
| Aberdare Developments Limited | Construction | 2003 |
| Aberdare Feet Ltd | Health & social care | 2024 |
| Aberdare Golf Club Trading Limited | Arts & recreation | 2021 |
| Aberdare Motors Ltd | Wholesale & retail | 2023 |
| Aberdare Park Boat and Kiosk Ltd | Hospitality | 2022 |
| Aberdare Post Ltd | Wholesale & retail | 2015 |
| Aberdare Rugby Union Football Club | Administrative & support | 2012 |
| Abernails Ltd | Other services | 2026 |
| Absolute Build Services Ltd | Construction | 2019 |
| Ace Landscaping Limited | Administrative & support | 1987 |
| ACL Commercial Services Limited | Professional & scientific | 2024 |
| ACN Construction Ltd | Construction | 2023 |
| Activate Construction Ltd | Construction | 2015 |
| Activate Property Group Ltd | Real estate | 2025 |
| Active Inspection Services Limited | Administrative & support | 2005 |
| Adelina Academy Ltd | Education | 2024 |
| ADK Drylining Ltd | Construction | 2026 |
| Adref - Home Ltd | Real estate | 2021 |
| Aesthetics by Louise Ltd | Wholesale & retail | 2025 |
| Afonbrook Consultancy Ltd | Professional & scientific | 2023 |
| AG Window & Door Repairs Ltd | Construction | 2024 |
| AG Worldwide Missions | Other services | 2017 |
| AGE Concern Morgannwg Limited | Other services | 2008 |
| AGE Concern Morgannwg Trading Limited | Financial services | 2000 |
| Aharaan Retails Ltd | Wholesale & retail | 2023 |
| AJL Consultancy Limited | Mining & quarrying | 2021 |
| AJP Cladding Ltd | Construction | 2022 |
| AJS Management Group Ltd | Financial services | 2023 |
| Akash Adhd Ltd | Health & social care | 2023 |
| Alaina Abrams Limited | Health & social care | 2025 |
| Albion Workplace Solutions Limited | Other services | 2009 |
| Albion WS Holdings Limited | Financial services | 2024 |
| Alfi Aberdare Limited | Hospitality | 2022 |
| ALI Baba Barber Ltd | Hospitality | 2017 |
| ALL Sealants Limited | Construction | 2015 |
| Allg Consultancy Limited | Financial services | 2016 |
| Alma 1965 Limited | Extraterritorial | 2015 |
| ALT Direct Ltd | Education | 2021 |
| ALT Surveying Limited | Professional & scientific | 1999 |
| Altitude Logistics Limited | Real estate | 2014 |
| Altitudemaintenance Services Ltd | Administrative & support | 2024 |
| Alto Building Consultants Limited | Construction | 2025 |
| Alto Project Consultants Limited | Construction | 2010 |
| Alusight Facade Design Ltd | Professional & scientific | 2024 |
| AM Removals and Clearances Ltd | Water & waste | 2025 |
| AM Shoes Limited | Wholesale & retail | 2025 |
| Aman Welding and Fabricating Ltd | Manufacturing | 2021 |
| Amarone Limited | Hospitality | 2024 |
| Amber Automotive Ltd | Wholesale & retail | 2025 |
| Amgen Rhondda Limited | Water & waste | 1998 |
| AMORE10 Limited | Hospitality | 2023 |
| ANA Amateur Boxing Club CIC | Arts & recreation | 2025 |
| Andover Nursing Services Limited | Health & social care | 2000 |
| Andrew Barratt Plant Hire Limited | Construction | 2015 |
| Andrew Forsythe Building Limited | Construction | 2005 |
| Andy Thomas UX Limited | Information & communication | 2026 |
| Anrhegion Cymreig CYF | Wholesale & retail | 2022 |
| Anthony Shopland 123 Limited | Other services | 2020 |
| AP Vapour DEN Ltd | Wholesale & retail | 2016 |
| Apexiar Limited | Information & communication | 2025 |
| Apollo Flooring Contracts Ltd | Construction | 2025 |
| Applied Science Knowledge Ltd | Information & communication | 2018 |
| Aqua Properties Cardiff Ltd | Real estate | 2019 |
| Aqua Vehicles Limited | Wholesale & retail | 2019 |
| Ardee Property Limited | Real estate | 2026 |
| Arkle Property Solutions Ltd | Real estate | 2020 |
| Artstudiocb Ltd | Arts & recreation | 2023 |
| Asco Associates Infrastructure Services Limited | Professional & scientific | 2024 |
| Asma Takeaway Ltd | Hospitality | 2025 |
| Aspire Developments (RCT) Ltd | Real estate | 2018 |
| Astra Plant Limited | Administrative & support | 2001 |