| ACR Building & Development Limited | Construction | 2024 |
| Acre Home Improvements Ltd | Construction | 2020 |
| ACS Ammanclad Ltd | Construction | 2024 |
| ACS Industrial & Mechanical Engineering Services Ltd. | Manufacturing | 2013 |
| ACT Student Support Ltd | Education | 2024 |
| Action for Elders UK C.I.C. | Health & social care | 2011 |
| Action Group Services Ltd | Professional & scientific | 2020 |
| Action Outreach Support Network CIC | Professional & scientific | 2026 |
| Action Petz Swansea Ltd | Arts & recreation | 2019 |
| Action Recruitment (Wales) Limited | Other services | 2009 |
| Actionfold Limited | Transport & logistics | 2018 |
| Active Air Products Ltd | Manufacturing | 2019 |
| Active Brand Concepts Limited | Wholesale & retail | 2009 |
| Active Indoor Leisure Swansea Limited | Arts & recreation | 2018 |
| Active Property Solutions (Wales) Limited | Real estate | 2014 |
| Activefactor Limited | Wholesale & retail | 1991 |
| Activemate Limited | Information & communication | 2020 |
| Actorize Limited | Information & communication | 2024 |
| AD Landscapes & Property Maintenance Ltd | Administrative & support | 2019 |
| AD Marketing Group Limited | Professional & scientific | 2018 |
| AD Technique Ltd | Construction | 2021 |
| AD Technology Consulting Limited | Information & communication | 2006 |
| AD2LYNX Ltd | Information & communication | 2019 |
| Adam Ford Project Management Limited | Construction | 2015 |
| Adam James Developments Ltd | Construction | 2012 |
| Adamandrews Ltd | Construction | 2018 |
| Adamian Thomas Consulting Limited | Professional & scientific | 2002 |
| Adamjee Creation Ltd | Wholesale & retail | 2020 |
| Adams X Football Ltd | Education | 2026 |
| Adamski Ltd | Wholesale & retail | 2021 |
| Adapt Business Services Limited | Administrative & support | 2009 |
| Adapt Property Services Limited | Real estate | 2017 |
| Adaptation Strategic Design Ltd | Professional & scientific | 2023 |
| ADB Building Limited | Construction | 2016 |
| Addasdy Ltd | Real estate | 2021 |
| Added Value Ltd | Extraterritorial | 2020 |
| Addo Creative | Arts & recreation | 2011 |
| ADE Enterprises Ltd | Extraterritorial | 2015 |
| Adedayo Oluwaseyi Adetunji Ltd | Health & social care | 2021 |
| Adelinas Events Ltd | Hospitality | 2023 |
| Adell Developments Ltd | Real estate | 2020 |
| Adept Employment Ltd | Administrative & support | 2020 |
| Adept Facilities Group Ltd | Administrative & support | 2015 |
| Adis Roofing Ltd | Construction | 2025 |
| Adisrutham Limited | Health & social care | 2016 |
| ADJ Surveying Ltd | Professional & scientific | 2024 |
| Adjam Limited | Construction | 2004 |
| Admiral Vending Systems Limited | Administrative & support | 2017 |
| ADN Supplies Ltd | Wholesale & retail | 2017 |
| ADR Financial Services Limited | Financial services | 2019 |
| Adrian & Victor Ltd | Hospitality | 2021 |
| Adrian Jeremiah Consulting Limited | Professional & scientific | 2016 |
| Adrian Muja Ltd | Transport & logistics | 2017 |
| ADS Welding & Fabrication Ltd | Manufacturing | 2023 |
| ADT Technical Ltd | Construction | 2021 |
| Advance Laparoscopic Surgery Ltd | Health & social care | 2011 |
| Advanced Brickwork Contractors Ltd. | Construction | 2011 |
| Advanced Materials Engineering Consultants Ltd. | Professional & scientific | 2013 |
| Advanced Timber Erecting Limited | Construction | 2019 |
| Advanced Web Technology Ltd | Manufacturing | 2014 |
| Adventures in Honeywood Ltd | Information & communication | 2023 |
| Advice UN Limited | Extraterritorial | 2014 |
| Advin Hand Car Wash Ltd | Wholesale & retail | 2025 |
| Adwagon Ltd | Transport & logistics | 2019 |
| Adwise Shepherd Ltd | Professional & scientific | 2025 |
| AE Davies Properties Ltd | Real estate | 2023 |
| Aegis Fire Safety Ltd | Public administration | 2026 |
| Aegp Ltd | Information & communication | 2017 |
| Ael-Y-Don Property Management Limited | Real estate | 1990 |
| AER (Removals) Ltd | Transport & logistics | 2020 |
| Aera Homes Ltd | Real estate | 2025 |
| Aerial Drone Surveys Ltd | Professional & scientific | 2016 |
| Aerial Optics Ltd | Construction | 2016 |
| Aerial Vehicles Limited | Wholesale & retail | 2023 |
| Aerospace & Aviation Consulting Services Limited | Administrative & support | 2013 |
| AES Payroll Services Ltd | Administrative & support | 2014 |
| Aesthetic Dreams Limited | Health & social care | 2025 |
| Aesthetic Kitchen Ltd | Hospitality | 2025 |
| Aesthetics by Alex Ltd | Other services | 2025 |
| Aesthetics by Kirsty Ltd | Health & social care | 2024 |
| AF Property Maintenance Group Ltd | Real estate | 2025 |
| Afan Logic Ltd | Information & communication | 2014 |
| Affect Ability Limited | Construction | 2017 |
| Afford Holdings Ltd | Professional & scientific | 2018 |
| Affordable Tyres Swansea Ltd | Wholesale & retail | 2025 |
| Afig Electronics Limited | Manufacturing | 1986 |
| AFM Property Holdings Ltd | Real estate | 2025 |
| Afon Holdings Limited | Professional & scientific | 2004 |
| Afon Lime Limited | Construction | 2020 |
| Afon Llan Limited | Extraterritorial | 2023 |
| Afon Toolmakers & Engineers Limited | Manufacturing | 1981 |
| Africaforex Trade and Partners Ltd | Wholesale & retail | 2025 |
| African Community Centre | Professional & scientific | 2007 |
| African Food and Spices Limited | Hospitality | 2023 |
| Afriroots & Routes CIC | Wholesale & retail | 2026 |
| Afro by Teecee Hair Care Ltd | Other services | 2025 |
| AFS Sprinklers Limited | Construction | 2026 |
| Aftc Ltd | Information & communication | 2005 |
| AG & G Property Holdings Ltd | Real estate | 2022 |
| AG Group Holdings Limited | Administrative & support | 2018 |