| Aryan Athavan Shaliny UK Limited | Wholesale & retail | 2024 |
| AS Soon AS Possible Ltd | Construction | 2025 |
| Asap Roofing & Building 2020 Ltd | Construction | 2020 |
| Asap Roofing & Building Ltd | Construction | 2026 |
| Asap Roofing Swansea Ltd | Construction | 2026 |
| Asbri Transport Limited | Construction | 2011 |
| Ascend Martial Arts Limited | Education | 2025 |
| Asco Service Ltd | Information & communication | 2013 |
| Ascot Technical Solutions Limited | Professional & scientific | 2021 |
| Ascotransit Ltd | Transport & logistics | 2023 |
| Ascus Screeding Ltd | Construction | 2013 |
| Asef Ltd | Real estate | 2019 |
| ASF Property Ltd | Real estate | 2024 |
| ASF UK Investments Ltd | Real estate | 2021 |
| ASH and Ryan Limited | Other services | 2024 |
| ASH Cost Consultancy Limited | Professional & scientific | 2007 |
| ASH Private Ltd | Wholesale & retail | 2024 |
| ASH Roofing & Cladding Limited | Construction | 2017 |
| Asher Thomas Limited | Health & social care | 2013 |
| Ashford Estate Agents Limited | Real estate | 2023 |
| Ashlan Trading Limited | Wholesale & retail | 1987 |
| Ashley Kissick Financial Advisers Ltd | Financial services | 2021 |
| Ashley Lewis Vehicle Tech Ltd | Wholesale & retail | 2025 |
| Ashmore & Allen Limited | Extraterritorial | 2010 |
| Ashton Distributors (Carpets) Limited | Wholesale & retail | 1978 |
| Ashvale Integrated Property Solutions Limited | Real estate | 1998 |
| Ashvale Properties UK Limited | Real estate | 2003 |
| ASI 2 Limited | Hospitality | 2019 |
| Asia Food Cardiff Ltd | Wholesale & retail | 2025 |
| Asia's European Car Parts Supermarket Limited | Extraterritorial | 2013 |
| ASJ Products Limited | Wholesale & retail | 2021 |
| ASJ Protection Ltd | Administrative & support | 2014 |
| ASL Boston Limited | Administrative & support | 2016 |
| Asmaa Almaliky Ltd | Health & social care | 2026 |
| ASN24 Properties Ltd | Real estate | 2025 |
| ASN5 Properties Ltd | Real estate | 2024 |
| Aspal Lane Management Limited | Professional & scientific | 2007 |
| Aspect Aluminium Limited | Construction | 2017 |
| Aspect Replacement Windows and Doors Ltd | Construction | 2023 |
| Aspinall Motors Ltd | Wholesale & retail | 2018 |
| Aspira Education Ltd | Administrative & support | 2025 |
| Aspire 41 Limited | Other services | 2021 |
| Asquith Electrical & Sons Ltd | Construction | 2022 |
| Asset Release Limited | Extraterritorial | 2012 |
| Asseticom Ltd | Professional & scientific | 2019 |
| Assetivo Ltd | Professional & scientific | 2019 |
| Assets Reimagined Ltd | Real estate | 2024 |
| Assets Stream Ltd | Real estate | 2022 |
| Assos Properties Ltd | Real estate | 2023 |
| Assos Vision Ltd | Health & social care | 2026 |
| Assura Quality Ltd | Professional & scientific | 2026 |
| Assurance Accountancy Ltd | Professional & scientific | 2012 |
| Assure Connect Ltd | Administrative & support | 2019 |
| Assure Developments Ltd | Construction | 2024 |
| Assure Sense Ltd | Information & communication | 2022 |
| AST Consulting Ltd | Administrative & support | 2024 |
| Astcal Limited | Construction | 2019 |
| Aster & Holly Cost Consultancy Ltd | Professional & scientific | 2025 |
| Asteris UK Holdings Ltd | Financial services | 2026 |
| Asteris UK Ltd | Professional & scientific | 2016 |
| Astley Samuel Leeder Ltd | Real estate | 1995 |
| Astralearners Ltd | Education | 2026 |
| Astro Consultancy Limited | Professional & scientific | 2012 |
| Astrosan Ltd | Real estate | 2022 |
| Astrum Construction Ltd | Construction | 2007 |
| Astute Online Tutoring Ltd | Education | 2026 |
| ASW Energy Services Limited | Construction | 2019 |
| ASW Property Services Limited | Construction | 2000 |
| AT Blossom Limited | Other services | 2023 |
| AT Holdings Limited | Professional & scientific | 2006 |
| ATB Contractors Ltd | Construction | 2024 |
| ATC FIN Ltd | Administrative & support | 2020 |
| ATEAM4HIRE Limited | Transport & logistics | 2018 |
| Atex Installations Ltd | Construction | 2015 |
| Athena Care Group Limited | Health & social care | 2013 |
| Athena Counselling Services Ltd | Information & communication | 2016 |
| Athena Forensics Limited | Administrative & support | 2008 |
| Athena Picture Agency Limited | Professional & scientific | 2011 |
| Athena Prop Co Limited | Households | 2026 |
| Athens Travel Ltd | Administrative & support | 2019 |
| Athleet Ltd | Information & communication | 2023 |
| Athlete Performance Preparation Ltd | Arts & recreation | 2023 |
| Athol Wellness Limited | Arts & recreation | 2026 |
| ATK Trading Limited | Professional & scientific | 2019 |
| Atkins Accountants Ltd | Professional & scientific | 1995 |
| Atkins Investment Group Limited | Financial services | 2023 |
| Atkins Ltd | Real estate | 2023 |
| ATL Water Process Ltd | Administrative & support | 2010 |
| Atlan Ltd | Construction | 2019 |
| Atlantic 03 Limited | Construction | 2003 |
| Atlantic Estates (Wales) Limited | Real estate | 1957 |
| Atlas AV Limited | Information & communication | 2010 |
| Atlas Bridge Group Ltd | Real estate | 2018 |
| Atlas Geophysical Limited | Information & communication | 2005 |
| Atlas Geotechnics Limited | Construction | 2020 |
| Atlas Paints Limited | Wholesale & retail | 2024 |
| Atlas Solar & Storage Limited | Construction | 2026 |
| Atol Flooring Ltd | Construction | 2024 |
| Atom Architecture Limited | Professional & scientific | 2006 |
| ATR Construction Ltd | Construction | 2021 |