| Assura Medical Centres Limited | Real estate | 2008 |
| Assura P1 Limited | Real estate | 2021 |
| Assura P2 Limited | Real estate | 2021 |
| Assura P3 Limited | Real estate | 2021 |
| Assura P4 Limited | Real estate | 2021 |
| Assura P5 Limited | Real estate | 2021 |
| Assura P6 Limited | Real estate | 2021 |
| Assura PCP UK Limited | Real estate | 2015 |
| Assura Primary Care Properties Limited | Real estate | 2013 |
| Assura Properties Limited | Real estate | 2007 |
| Assura Properties UK Limited | Real estate | 2007 |
| Assura Property Management Limited | Administrative & support | 2008 |
| Assura Services Limited | Financial services | 2003 |
| Assura Solaris Limited | Energy | 2023 |
| Assura Trellech Limited | Real estate | 2011 |
| Assure Microbiology Consultancy Limited | Professional & scientific | 2026 |
| Assure Testing Limited | Information & communication | 2025 |
| Assured Building Limited | Construction | 2026 |
| Assured Clarity Limited | Information & communication | 2013 |
| Assured Privacy Consulting Limited | Professional & scientific | 2018 |
| Astartes Strategic Ltd | Professional & scientific | 2026 |
| Astbury FD Limited | Professional & scientific | 2012 |
| Astek Innovations Limited | Wholesale & retail | 2004 |
| Asteris AI Ltd | Information & communication | 2025 |
| Asterlush UK Ltd | Real estate | 2021 |
| Astermark Limited | Households | 1998 |
| Astranis UK Limited | Manufacturing | 2022 |
| Astretch Ltd | Education | 2026 |
| Astro Blue Homes Ltd | Construction | 2025 |
| Astro Nano Limited | Professional & scientific | 2016 |
| Astronautx Limited | Professional & scientific | 2019 |
| Asymmetrix Partners Limited | Financial services | 2024 |
| AT Holdings (NW) Ltd | Financial services | 2016 |
| AT Sky Ltd | Hospitality | 2022 |
| AT Superstore Limited | Wholesale & retail | 2022 |
| Atal Consulting Limited | Professional & scientific | 2020 |
| Atassi Property Ltd | Real estate | 2024 |
| Atassi Property Partners Ltd | Real estate | 2025 |
| ATC (North) Limited | Education | 1988 |
| ATC Nails & Beauty Limited | Other services | 2023 |
| Atelier CLO Ltd | Professional & scientific | 2021 |
| Atelier LAL Limited | Professional & scientific | 2025 |
| ATG Surveying Ltd | Professional & scientific | 2023 |
| Atharva Software Solutions Limited | Information & communication | 2019 |
| Athol Vale Limited | Real estate | 2022 |
| Athrú Group Limited | Professional & scientific | 2022 |
| Atiba Life Science Consulting Limited | Administrative & support | 2021 |
| Atkins Building Solutions Ltd | Construction | 2010 |
| Atlantic Digital Marketing Limited | Information & communication | 2019 |
| Atlantic Garage Limited | Wholesale & retail | 2025 |
| Atlantic Property & Constructions Limited | Construction | 2023 |
| Atlantic Property Group Ltd | Real estate | 2019 |
| Atlantic Timber Company Limited | Wholesale & retail | 1981 |
| Atlas Commercial Group Ltd | Wholesale & retail | 2026 |
| Atlas MSP Group Limited | Information & communication | 2025 |
| ATM Creative Ltd | Professional & scientific | 2023 |
| Atmos Data Services Limited | Information & communication | 2009 |
| Atmosphere Roofing Limited | Construction | 2023 |
| ATO Solutions Limited | Professional & scientific | 2019 |
| Atomic Travel Ltd | Administrative & support | 2009 |
| Atomistic Ltd | Professional & scientific | 2021 |
| Atrakt Limited | Professional & scientific | 2000 |
| Atron Property Limited | Real estate | 2021 |
| Atrus Property Consulting Ltd | Professional & scientific | 2025 |
| Attache Limited | Financial services | 2000 |
| Attenbury Holdings Limited | Construction | 2025 |
| Attic Build & FIX Company Ltd | Construction | 2023 |
| Atticus & Indi Coffee Ltd | Hospitality | 2025 |
| Atticus Promotions Ltd | Wholesale & retail | 2011 |
| Attila Marketing (UK) Limited | Wholesale & retail | 1996 |
| Atzconsultanting Limited | Professional & scientific | 2019 |
| Audenshaw Court Flat Management Limited | Households | 2000 |
| Audenshaw Trading Limited | Wholesale & retail | 2024 |
| Audio Input Ltd | Manufacturing | 2023 |
| Audion Global Ltd | Information & communication | 2018 |
| Aumoma Ltd | Health & social care | 2013 |
| Aumudita Healthcare Ltd | Health & social care | 2025 |
| Auras Consulting Limited | Professional & scientific | 2022 |
| Auravel Capital Limited | Information & communication | 2025 |
| Aurevon Security Ltd | Information & communication | 2026 |
| Aurex Project & Programme Consultancy Limited | Information & communication | 2025 |
| Auric Design Studio Ltd | Professional & scientific | 2014 |
| Aurium Resources Limited | Professional & scientific | 2023 |
| Auscash Limited | Financial services | 1993 |
| Austin & Wyatt Limited | Professional & scientific | 1994 |
| Authorised Compliance Ltd. | Public administration | 2024 |
| Autism Care Everywhere Ltd | Other services | 2016 |
| Autism Trafford Educational Services Ltd | Education | 2025 |
| Auto Logistiks Limited | Transport & logistics | 2015 |
| Autoexec Limited | Professional & scientific | 2022 |
| Automated Habitat Limited | Construction | 2009 |
| Autonics UK Limited | Wholesale & retail | 2012 |
| Auumai Limited | Information & communication | 2025 |
| AVA Rose Interiors Limited | Professional & scientific | 2026 |
| Avalon Airships Ltd | Manufacturing | 2017 |
| Avalon Court Ltd | Households | 2014 |
| Avant-Garde Optical Limited | Other services | 2015 |
| AVE BIM Ltd | Professional & scientific | 2018 |
| Avenco Limited | Construction | 2025 |
| Avenham Road Fraser Homes Limited | Construction | 2022 |