| A2H Live Holding Limited | Financial services | 2023 |
| A2Z Automotives Ltd | Wholesale & retail | 2024 |
| A2Z-COMPUTING Ltd | Information & communication | 2000 |
| A3O1 Ltd | Wholesale & retail | 2024 |
| A4 Safety Ltd | Professional & scientific | 2021 |
| AA Aluminium Limited | Construction | 2024 |
| AA Bendon Construction Limited | Construction | 2018 |
| AA Pro Cleaning Limited | Administrative & support | 2026 |
| AA Rendering Ltd | Construction | 2026 |
| AA432 Ltd | Hospitality | 2020 |
| AAF Development Ltd | Construction | 2025 |
| AAF Distributions Ltd | Construction | 2025 |
| Aafs Properties Ltd | Real estate | 2022 |
| Aalo Limited | Hospitality | 2016 |
| Aaltmo Ltd | Construction | 2024 |
| Aamer Iqbal Medicare Ltd | Health & social care | 2012 |
| Aaragon Solutions Limited | Information & communication | 2008 |
| AB4 Promotions Ltd | Arts & recreation | 2020 |
| AB4 Properties Ltd | Real estate | 2020 |
| Abacus Advanced Automotive Services Limited | Wholesale & retail | 2009 |
| Abacus AFS Holdings Ltd | Financial services | 2025 |
| Abacus Assurance Financial Services Limited | Financial services | 2006 |
| Abacus Bookkeeping and Accounts Limited | Professional & scientific | 2013 |
| Abboo Finance Limited | Financial services | 2021 |
| Abbot Close Road Management Limited | Extraterritorial | 2016 |
| Abby Transport Services Limited | Transport & logistics | 2017 |
| ABC Care Newport Ltd | Health & social care | 2024 |
| ABC Deli Holdings Ltd | Financial services | 2024 |
| ABC Delikatesy Ltd | Wholesale & retail | 2015 |
| ABC Taxis (Newport) Limited | Transport & logistics | 2017 |
| ABC Traders (Newport) Ltd | Wholesale & retail | 2025 |
| Abcseller Ltd | Wholesale & retail | 2025 |
| Abdur Rahman Ltd | Hospitality | 2025 |
| Abeeso Security and Cleaning Services Ltd | Administrative & support | 2021 |
| Abel Construction Group Ltd | Construction | 2022 |
| Abels Group Limited | Administrative & support | 2017 |
| Aber Locksmith Services Ltd | Construction | 2005 |
| Abetter Health Ltd | Health & social care | 2021 |
| ABI Abley Photography Limited | Professional & scientific | 2017 |
| ABI IOW Limited | Wholesale & retail | 2022 |
| Abiac Bulk Handling Limited | Professional & scientific | 2014 |
| Abienjie Limited | Health & social care | 2021 |
| ABJ Direct Ltd | Wholesale & retail | 2025 |
| Able Calibration Services Ltd | Professional & scientific | 2006 |
| Ablr Holding Limited | Professional & scientific | 2024 |
| ABM Cafe Express Limited | Hospitality | 2025 |
| ABN Assets Limited | Real estate | 2016 |
| ABN Stone Limited | Manufacturing | 2022 |
| Abnormal Load Transport Limited | Transport & logistics | 2019 |
| Abode (IW) Ltd | Real estate | 2026 |
| Above & Beyond Design and Build Ltd | Construction | 2020 |
| ABR Gwent Ltd | Wholesale & retail | 2021 |
| Abraham & Sons Property Ltd | Real estate | 2017 |
| Abraxas Business Consulting Limited | Information & communication | 2015 |
| Absarhlute Shine Limited | Administrative & support | 2025 |
| Absolute Events Services Ltd | Hospitality | 2021 |
| Absolute Property Holdings Ltd | Real estate | 2016 |
| Abuker Limited | Wholesale & retail | 2025 |
| AC Auto Repairs Ltd | Wholesale & retail | 2018 |
| AC Electrical Contractors IW Ltd | Construction | 2023 |
| AC Engineering & Design Limited | Professional & scientific | 2009 |
| Ac&Ar Decorating Solutions Ltd | Construction | 2025 |
| AC5 Properties Ltd | Real estate | 2022 |
| Acaml Ltd | Manufacturing | 2026 |
| Accent on Education Limited | Administrative & support | 2010 |
| Access 4/20 Management Limited | Real estate | 2006 |
| Accident Repair Centre Newport Limited | Wholesale & retail | 2020 |
| Accommodation Transformation Ltd | Real estate | 2025 |
| Accountart Tax Services Ltd | Professional & scientific | 2004 |
| Accudyne Europe Limited | Manufacturing | 2018 |
| Accurate Books Limited | Professional & scientific | 2017 |
| Ace Alloy Centre Limited | Wholesale & retail | 2025 |
| Ace Asset Management Solutions Ltd | Real estate | 2025 |
| Ace Aviation Ltd | Manufacturing | 2024 |
| Ace Computer Systems (UK) Ltd | Other services | 2003 |
| Ace Dynasty Limited | Professional & scientific | 2012 |
| Ace Homes Rental and Renovations Ltd | Real estate | 2023 |
| Ace Language & Business Services Limited | Professional & scientific | 2009 |
| Ace Metalfabs Limited | Manufacturing | 2022 |
| Ace Mobile Tyres Ltd | Wholesale & retail | 2022 |
| Ace Performance Cars Limited | Manufacturing | 2011 |
| Ace Tyres Ltd | Wholesale & retail | 2020 |
| Ace-Vy Technologies Limited | Information & communication | 2025 |
| Acer Manufacturing Limited | Real estate | 2010 |
| Aces Signature Clothing Limited | Wholesale & retail | 2021 |
| ACL Contractor Solutions Limited | Construction | 2022 |
| Acns Electrical Limited | Construction | 2016 |
| Acorn Global Recruitment Limited | Administrative & support | 1997 |
| Acorn Rail Limited | Administrative & support | 2009 |
| Acorn Roofing South Wales Ltd | Construction | 2023 |
| ACOUSTICA54 Ltd | Hospitality | 2023 |
| Acoustics & Noise Limited | Professional & scientific | 2006 |
| Acquis Data Services Limited | Information & communication | 2022 |
| Acquis Holding Limited | Financial services | 2014 |
| Acquis Insurance Management Limited | Financial services | 2009 |
| Acquis Nominee Limited | Financial services | 2021 |
| ACS Group Limited | Professional & scientific | 2008 |
| ACS Oakdale Limited | Professional & scientific | 2025 |
| Acsendgrowth Ltd | Information & communication | 2025 |
| ACT Happy Ltd | Information & communication | 2024 |