| Ashley-Edison International Limited | Manufacturing | 2006 |
| Ashton & Spencer Holdings Limited | Real estate | 2016 |
| Ashurst Plant Limited | Construction | 1988 |
| Ashvale Sawmills Limited | Manufacturing | 1979 |
| Ashwani's Food Ltd | Hospitality | 2025 |
| Ashwaytrading Ltd | Wholesale & retail | 2024 |
| Asilya Holdings Ltd | Real estate | 2024 |
| Asjc Consulting Limited | Professional & scientific | 2017 |
| ASK the Producers Limited | Professional & scientific | 2005 |
| Askew Family Investments Limited | Households | 2021 |
| Askival Systems Limited | Information & communication | 1986 |
| Asla Development Limited | Construction | 2018 |
| ASM Family Investments Limited | Financial services | 2026 |
| Asml Holdings Ltd | Real estate | 2023 |
| Aspect 23 Limited | Information & communication | 2013 |
| Aspect Car Sales Limited | Wholesale & retail | 2021 |
| Aspect Cranleigh Limited | Manufacturing | 2013 |
| Aspect Installation & Engineering Services Limited | Manufacturing | 2002 |
| Aspect Managements Limited | Real estate | 1964 |
| Aspen Homes Limited | Administrative & support | 2009 |
| Aspenarb Limited | Agriculture & fishing | 2015 |
| Aspenone Ltd | Energy | 2022 |
| Asperion Group Limited | Hospitality | 2015 |
| Aspire Digital Services Limited | Wholesale & retail | 2023 |
| ASR Investments Limited | Real estate | 2014 |
| Assagai Ltd | Real estate | 2025 |
| Assesstech Limited | Professional & scientific | 2010 |
| Assets and Gold Limited | Financial services | 2023 |
| Associated Neighbour Training Limited | Administrative & support | 2016 |
| Association of Planning Engineers Limited | Other services | 2020 |
| Assure Build Ltd | Construction | 2011 |
| Aston Business Assessments Limited | Professional & scientific | 2010 |
| Astra House (IOW) Limited | Real estate | 2009 |
| Astrea Energies Europe Ltd | Manufacturing | 2023 |
| Astro Accountants Limited | Administrative & support | 2016 |
| Astro Properties Ltd | Real estate | 2017 |
| Astute Digital Solutions Ltd | Information & communication | 2014 |
| Asynjur PA Services Ltd | Administrative & support | 2016 |
| At-Risk International UK Limited | Administrative & support | 2021 |
| Athame Games Ltd | Information & communication | 2026 |
| Athanz Group Limited | Wholesale & retail | 2025 |
| Athena Infinite Spirit Ltd | Financial services | 2018 |
| Athena Know-How Limited | Professional & scientific | 2016 |
| Atherfield Consulting Ltd | Professional & scientific | 2020 |
| Athlete Image Group Limited | Professional & scientific | 2026 |
| Athletic Performance Group Limited | Arts & recreation | 2024 |
| Atkinson Synergy Ltd | Information & communication | 1988 |
| Atlanta Bidco Limited | Information & communication | 2018 |
| Atlanta Midco Limited | Information & communication | 2018 |
| Atlanta Topco Limited | Information & communication | 2018 |
| Atlas Power Engineering Ltd | Administrative & support | 2022 |
| ATM Merrow Ltd | Hospitality | 2024 |
| Atmosair Limited | Administrative & support | 2001 |
| Atomy Distribution Limited | Wholesale & retail | 2020 |
| Atran Business Services Ltd | Real estate | 2023 |
| ATS Training Limited | Professional & scientific | 2009 |
| Attachview Properties Limited | Extraterritorial | 1982 |
| Atters Investments Limited | Financial services | 2026 |
| Attic Design and Build Ltd | Construction | 2021 |
| Attleborough Estates Limited | Real estate | 1992 |
| Attwood Digital Marketing Limited | Administrative & support | 2018 |
| Atwal Fitness Ltd | Arts & recreation | 2022 |
| Atwal Property Investments Limited | Real estate | 2004 |
| AU Applegarth Limited | Health & social care | 2022 |
| AU Courant Solutions Ltd | Financial services | 2017 |
| Auckland Consulting Ltd | Professional & scientific | 2021 |
| Audio Production & Supply Ltd | Information & communication | 2012 |
| Audio Visual Upcycle Ltd | Professional & scientific | 2018 |
| Augmentti Ltd | Administrative & support | 2018 |
| AUM Lettings Ltd | Real estate | 2024 |
| Auntie Esme's Pet Grooming Ltd | Professional & scientific | 2019 |
| Aura Veterinary Limited | Professional & scientific | 2013 |
| Auremus Ltd | Hospitality | 2019 |
| Aurivo Homes Limited | Real estate | 2025 |
| Aurora Ophthalmology UK Ltd | Professional & scientific | 2020 |
| Austin Buryfields Limited | Real estate | 2016 |
| Authentica Limited | Other services | 2013 |
| Authie Nilda Cleaning Ltd | Administrative & support | 2023 |
| Auto Carwash and Cleaning Ltd | Administrative & support | 2026 |
| Autofreight Limited | Transport & logistics | 1991 |
| Autonomous Global Solutions Ltd | Transport & logistics | 2024 |
| Autumn Sun Holdings Limited | Financial services | 2016 |
| Auxana Ltd | Information & communication | 2025 |
| Auxilio Vide Veritatem Ltd | Professional & scientific | 2025 |
| Auxilium (Moodiesburn 2025) Ltd | Construction | 2025 |
| Auxilium Advisers Limited | Professional & scientific | 2015 |
| AV Design Consulting Ltd | Professional & scientific | 2024 |
| AV Music Ltd | Arts & recreation | 2020 |
| AV Solutions Group Limited | Construction | 2018 |
| Avalon Advisory Limited | Professional & scientific | 2013 |
| Avance Events Ltd | Arts & recreation | 2020 |
| Aveling Construction Ltd | Administrative & support | 1998 |
| Avery Electrical (Guildford) Limited | Construction | 1975 |
| Aviation Structures Support Limited | Administrative & support | 2011 |
| Avisene Ventures Limited | Administrative & support | 2018 |
| Avita Social Care Ltd | Public administration | 2025 |
| AVO TV Limited | Information & communication | 2019 |
| Avon Court Management (Guildford) Limited | Administrative & support | 1973 |
| Avoria Ventures Ltd | Wholesale & retail | 2026 |
| Awaa Limited | Professional & scientific | 2019 |