| AG Llynfi Ltd. | Health & social care | 2026 |
| AG Project Management Solutions Limited | Professional & scientific | 2015 |
| AG Properties & Maintenance Ltd | Real estate | 2017 |
| AG Removals & Transport Ltd | Transport & logistics | 2025 |
| AG Social Work Services Ltd | Health & social care | 2022 |
| AG Superstores Ltd | Wholesale & retail | 2021 |
| AGC Engineering Services Ltd | Construction | 2025 |
| Agdcare Ltd | Health & social care | 2024 |
| AGE Cymru West Glamorgan Limited | Extraterritorial | 2011 |
| Agile Solution House Ltd | Information & communication | 2011 |
| AGJ Farming & Logistics Limited | Agriculture & fishing | 2026 |
| Aglec Electrical Ltd | Construction | 2019 |
| Aglow International Lighting Ltd | Wholesale & retail | 2018 |
| Agryin Ltd | Financial services | 2025 |
| AGS Specialist Joinery Limited | Manufacturing | 2006 |
| AH Motor Sales Ltd | Wholesale & retail | 2025 |
| Ahcd Properties Ltd | Real estate | 2003 |
| AHE Properties Limited | Real estate | 2011 |
| Ahead Services (UK) Limited | Administrative & support | 2011 |
| Ahmed & Islam Ltd | Hospitality | 2024 |
| AHT Property Management Limited | Real estate | 2021 |
| AI Client Care Limited | Information & communication | 2024 |
| AID Holdings Limited | Real estate | 2020 |
| Aika Furniture Trading Limited | Wholesale & retail | 2018 |
| Ailan Limited | Administrative & support | 2022 |
| Ailsa Craig Trading Co Limited | Real estate | 1990 |
| Aimancer Ltd | Information & communication | 2025 |
| Aimee Thomas Properties Ltd | Real estate | 2025 |
| Aimsafe Consulting Ltd | Information & communication | 2026 |
| Aimz Cabs Ltd | Transport & logistics | 2025 |
| Air Shot Limited | Wholesale & retail | 2014 |
| Air Source Energy South Wales Limited | Construction | 2022 |
| Airbridge Ltd | Wholesale & retail | 2024 |
| Airfield Metals Limited | Administrative & support | 2015 |
| Aizelax Limited | Professional & scientific | 2024 |
| AJ Delite Ltd | Hospitality | 2026 |
| AJ Engineering Group Limited | Other services | 2019 |
| AJ Event Catering Ltd | Hospitality | 2016 |
| AJ House Solutions Limited | Real estate | 2025 |
| AJ Inspection Limited | Professional & scientific | 2007 |
| AJ Platinum Building Limited | Construction | 2025 |
| AJ Property Services (Swansea) Ltd | Construction | 2021 |
| AJ Rees Holdings Ltd | Wholesale & retail | 2025 |
| AJ Security Group Limited | Administrative & support | 2024 |
| AJ Watersports Ltd | Transport & logistics | 2025 |
| AJ Williams Electrical Services Ltd | Construction | 2021 |
| AJB Business Solutions Ltd | Professional & scientific | 2013 |
| AJB Precision Limited | Professional & scientific | 2014 |
| AJC Developments Ltd | Real estate | 2000 |
| AJD Cardiff Properties Limited | Real estate | 2018 |
| AJF Rentals Ltd | Real estate | 2021 |
| AJG Property Management Ltd | Real estate | 2023 |
| AJH Financial Services Ltd | Financial services | 1999 |
| Ajjo Ltd | Real estate | 2023 |
| AJL Hydro Ltd | Professional & scientific | 2018 |
| AJS Consulting Services Limited | Professional & scientific | 2016 |
| Ajsl Engineering Limited | Construction | 2017 |
| Ajslproperty Ltd | Real estate | 2024 |
| AJT Content Creations Ltd | Arts & recreation | 2023 |
| Ajustar 24 Care Ltd | Health & social care | 2019 |
| AJW Business Associates Limited | Financial services | 2014 |
| AJW Properties Management Limited | Real estate | 2019 |
| AK Aura Limited | Wholesale & retail | 2025 |
| AK Davies Property Ltd | Real estate | 2024 |
| AK Food House Ltd | Hospitality | 2026 |
| AKA Research Limited | Professional & scientific | 2016 |
| Akab Enterprises Ltd | Real estate | 2025 |
| Akalifamcare Ltd | Health & social care | 2024 |
| Akbar's Swansea Ltd | Hospitality | 2025 |
| Akcg Ltd | Real estate | 2026 |
| Akhami Ltd | Wholesale & retail | 2025 |
| Akhamiaali Ltd | Construction | 2023 |
| Akhtar SA Ltd | Information & communication | 2015 |
| Akreo Ltd | Professional & scientific | 2024 |
| Akrivia Engineering Ltd | Construction | 2016 |
| Aksr Store Ltd | Wholesale & retail | 2024 |
| Aksu Town Grill Ltd | Hospitality | 2019 |
| AKT Roller Shutters Ltd | Manufacturing | 2023 |
| AKZ Security Systems Ltd | Administrative & support | 2018 |
| AL Imran Exchange Limited | Administrative & support | 2014 |
| AL Kasid Enterprises (UK) Ltd. | Wholesale & retail | 2022 |
| AL Noon Consulting Limited | Professional & scientific | 2012 |
| AL Quba Travels Ltd | Administrative & support | 2025 |
| Alan & Natan Properties Ltd | Real estate | 2023 |
| Alan Hancock Aluminium Doors & Windows Limited | Construction | 2009 |
| Alaska Barber Ltd | Other services | 2024 |
| Alaya Mortgages Ltd | Financial services | 2026 |
| Albert James Services Limited | Professional & scientific | 2020 |
| Albion Computer Services Limited | Professional & scientific | 1978 |
| Albion Technologies Ltd | Manufacturing | 2019 |
| Albita Properties Ltd | Real estate | 2019 |
| Albosc Ltd | Construction | 2022 |
| Alchemist Solutions Limited | Professional & scientific | 2019 |
| Alchemy Technologies Limited | Manufacturing | 2002 |
| Alchimica Building Chemicals Ltd | Wholesale & retail | 2014 |
| Alchimica UK Ltd | Wholesale & retail | 2018 |
| Alcohol UN Limited | Extraterritorial | 2023 |
| Alcolock UK Limited | Wholesale & retail | 2003 |
| Aldalati Medical Ltd | Health & social care | 2025 |
| Aldeb Investments Ltd | Real estate | 2018 |