| Aldeco Limited | Construction | 2018 |
| Alden's Ltd | Hospitality | 2015 |
| Alder Jones Properties Ltd | Real estate | 2024 |
| Aldergold Limited | Hospitality | 2001 |
| Alders Transport Ltd | Transport & logistics | 2026 |
| ALE Marketing Ltd | Wholesale & retail | 2019 |
| ALE Rooms Ltd | Administrative & support | 2016 |
| Aled Thomas Foot Trimming Limited | Agriculture & fishing | 2005 |
| ALETALAN1206 Limited | Professional & scientific | 2024 |
| Alex Borsden Limited | Health & social care | 2022 |
| Alex Lewis (Llandewi Garage) Ltd | Wholesale & retail | 2019 |
| Alex Owens Painting and Decorating Services Ltd | Construction | 2026 |
| Alex Thomas Property Management Limited | Real estate | 2019 |
| Alexa Care Recruitment Ltd | Administrative & support | 2023 |
| Alexander Briggs Limited | Administrative & support | 1997 |
| Alexander Douglas Limited | Financial services | 2014 |
| Alexanders Associates Limited | Information & communication | 2010 |
| Alexandrite Property Developments Ltd | Real estate | 2025 |
| Alexdraft Limited | Real estate | 1995 |
| Alfa Catering Limited | Hospitality | 2024 |
| Alfa Inc Ltd | Health & social care | 2012 |
| Alfordmet Limited | Health & social care | 2024 |
| Alfredo Ltd. | Other services | 1998 |
| ALG Racing Limited | Professional & scientific | 2008 |
| Algae Products International Ltd | Manufacturing | 2023 |
| Algar Groundworks Limited | Construction | 2015 |
| ALH Design Solutions Ltd | Professional & scientific | 2023 |
| Ali's Kebabs (Llansamlet) Ltd | Hospitality | 2017 |
| Alies-Fennell Ltd | Real estate | 2025 |
| Align Therapies Limited | Health & social care | 2018 |
| Aligned Life Solutions Limited | Professional & scientific | 2025 |
| Aliment Ltd. | Administrative & support | 2004 |
| ALJ Holdings Limited | Real estate | 2017 |
| ALJ Pharma Ltd | Wholesale & retail | 2020 |
| ALK Properties Limited | Real estate | 2018 |
| Alkel Homes Limited | Construction | 2013 |
| Alkimia C.I.C. | Information & communication | 2020 |
| ALL 4 YOU Contractors Ltd | Construction | 2017 |
| ALL About Ltd | Construction | 2024 |
| ALL Bright Cleaning Ltd | Administrative & support | 2021 |
| ALL Cars Bought for Cash Ltd | Wholesale & retail | 2023 |
| ALL Chrome Limited | Manufacturing | 2009 |
| ALL Heights Wales Ltd | Construction | 2024 |
| ALL in One Home and Garden Projects Ltd | Administrative & support | 2023 |
| ALL OR Nothing Barbershop Limited | Other services | 2019 |
| ALL Revved UP Motorcycles Ltd | Wholesale & retail | 2020 |
| ALL Seasons Gourmet Limited | Hospitality | 2009 |
| ALL Town Metals Ltd | Extraterritorial | 2014 |
| ALL Wales Ambulance Services Limited | Health & social care | 1999 |
| ALL Waste Services Ltd | Water & waste | 2002 |
| ALL Ways Trading Limited | Wholesale & retail | 2020 |
| ALL Wheels Alloy Ltd | Wholesale & retail | 2011 |
| Allavare Ltd | Manufacturing | 2021 |
| Allchurch & Co Limited | Professional & scientific | 2016 |
| Allegro Travel Ltd | Administrative & support | 2009 |
| Allen Finance Limited | Financial services | 2015 |
| Alliance International Asset Management Ltd | Administrative & support | 2017 |
| Alliance Temps Ltd | Administrative & support | 2020 |
| Allied & Nationwide Developments Limited | Real estate | 2006 |
| Allied Assist Ltd | Financial services | 2019 |
| Allied Design Consultancy (UK) Limited | Professional & scientific | 2000 |
| Allied Homes Limited | Real estate | 2021 |
| Allied Medicare Limited | Health & social care | 2024 |
| Allied Solutions Limited | Professional & scientific | 2004 |
| Allies of Travel Limited | Wholesale & retail | 2025 |
| Allison Jayne (Swansea) Limited | Wholesale & retail | 2003 |
| Allison Jayne Bristol Limited | Administrative & support | 2011 |
| Allison Jayne Limited | Wholesale & retail | 1987 |
| Allison Park Holdings Limited | Professional & scientific | 2011 |
| Allisstone Leisure Limited | Hospitality | 2024 |
| Allmodcons Ltd | Agriculture & fishing | 2003 |
| Allson Ltd | Manufacturing | 2025 |
| Alltiago Close Management Company Limited | Real estate | 2013 |
| Alltwen Building & Maintenance Limited | Construction | 2017 |
| Alltwen Marine Ltd | Professional & scientific | 2021 |
| Allvolt Electrical Ltd | Construction | 2024 |
| ALMA22MEDIA Limited | Other services | 2025 |
| Almond & Pearl Properties Limited | Real estate | 2017 |
| Aln-Connect CIC | Other services | 2025 |
| Aloucar Ltd | Wholesale & retail | 2021 |
| ALPARSLAN68 Ltd | Hospitality | 2023 |
| Alpha Bravo 999 Limited | Information & communication | 2021 |
| Alpha Electrics Contracting Limited | Manufacturing | 2002 |
| Alpha Mane Ltd | Other services | 2023 |
| Alpha R2 Limited | Financial services | 2016 |
| Alpha Roofing & Building Ltd | Construction | 2024 |
| Alpha Safety Training Limited | Education | 2010 |
| Alpha Upvc Limited | Construction | 2019 |
| ALPHA1 Living Ltd | Hospitality | 2025 |
| Alphacom Modelling Ltd | Information & communication | 2000 |
| Alphafloor Ltd | Construction | 2023 |
| Alphat Consulting Limited | Professional & scientific | 2016 |
| Alphateq Services Ltd | Energy | 2019 |
| Alpine Mechanical Limited | Construction | 2018 |
| ALR Assets & Holdings Limited | Financial services | 2025 |
| ALS Carpets and Flooring Ltd | Construction | 2025 |
| ALS Property Maintenance Limited | Manufacturing | 2019 |
| Alsaab-Tech Ltd | Information & communication | 2022 |
| Alsaieed Properties Ltd | Real estate | 2023 |
| Altamar Management (Swansea) Limited | Households | 2005 |