| Allan Holdings Limited | Real estate | 2018 |
| Allen Homes (Central Midlands) Ltd | Extraterritorial | 1992 |
| Allen Homes (North Midlands) Ltd | Professional & scientific | 1988 |
| Allen Homes (North Wales) Limited | Professional & scientific | 1990 |
| Allen Homes (North West) Ltd. | Professional & scientific | 1977 |
| Allen Homes (Yorkshire) Limited | Professional & scientific | 1976 |
| Allen Homes Limited | Professional & scientific | 1933 |
| Alliance Paraplanning Limited | Administrative & support | 2013 |
| Allinson Consulting Limited | Professional & scientific | 2009 |
| Allshaw Group Limited | Construction | 2020 |
| Almamicaus Ltd | Health & social care | 2022 |
| Almas Homes Ltd | Real estate | 2023 |
| Alpenza Ltd | Construction | 2024 |
| Alpha Building Supplies Limited | Wholesale & retail | 2004 |
| Alpin Tiling Limited | Construction | 2025 |
| Alpine Security Systems Limited | Manufacturing | 2015 |
| Alsened Limited | Hospitality | 2013 |
| Alston Medical Limited | Health & social care | 2025 |
| ALT Brick Invest Ltd | Real estate | 2018 |
| Alther Solutions Ltd | Professional & scientific | 2018 |
| Altofocus Limited | Professional & scientific | 2015 |
| Aluci Enterprises Ltd | Real estate | 2020 |
| AM MLR & Consulting Ltd | Professional & scientific | 2024 |
| Amanda Boyd Consultancy Ltd | Extraterritorial | 2017 |
| Amanda Wyatt Holdings Limited | Financial services | 2014 |
| Amaris Medical Limited | Health & social care | 2015 |
| Amava Group Limited | Real estate | 2023 |
| Amazing Sports Tours Ltd | Arts & recreation | 2024 |
| AMB Property Trading Ltd | Real estate | 2021 |
| Amber & Oscar Ltd | Wholesale & retail | 2020 |
| Amber IFA Company Limited | Financial services | 2013 |
| Amber Management Consultants Limited | Professional & scientific | 2026 |
| Amberis Legal Assistance Limited | Administrative & support | 2016 |
| Amberside ALP Limited | Financial services | 2017 |
| Ambika Building Services Limited | Construction | 2008 |
| Amble Property Holdings Ltd | Real estate | 2020 |
| American Nails Studio Limited | Other services | 2015 |
| Amersham Dental Care Limited | Health & social care | 2008 |
| Amigo Hospitality Limited | Hospitality | 2024 |
| Aminitee Ltd | Hospitality | 2025 |
| Amiry Investments Limited | Real estate | 2025 |
| Amor Fati Legal Limited | Professional & scientific | 2020 |
| Amorage Limited | Health & social care | 2014 |
| Amptl LLP | | 2020 |
| AMS Skip Hire Cheshire Limited | Other services | 2026 |
| Amtrex International Limited | Wholesale & retail | 2017 |
| AN Expert of Sorts Ltd | Other services | 2025 |
| An-Aesthetic Specialists Ltd | Health & social care | 2016 |
| Anaesthesia Manchester Limited | Health & social care | 2016 |
| Anaesthetic Medical Distribution Ltd | Professional & scientific | 2022 |
| Anaesthetic Medical Systems Ltd | Manufacturing | 1999 |
| Anapatru Property Management Ltd | Real estate | 2025 |
| Anar Retail Ltd | Wholesale & retail | 2018 |
| Anatinae Partnership LLP | | 2026 |
| Anderson Medical and Technical Services Limited | Professional & scientific | 1992 |
| Andrew Johnson Consultancy Limited | Professional & scientific | 2016 |
| Andrew Marchetti Ltd | Health & social care | 2015 |
| Andrew Porter Rheumatology Ltd | Health & social care | 2025 |
| Andromeda Cleaning Service Ltd | Administrative & support | 2011 |
| Anew Design Ltd | Professional & scientific | 2009 |
| ANG Medical Imaging Ltd | Health & social care | 2025 |
| Angel Accounting Solutions Ltd | Professional & scientific | 2023 |
| Angel Approved Ltd | Administrative & support | 2021 |
| Angel Health Limited | Health & social care | 2025 |
| Angela Private Ltd | Health & social care | 2016 |
| Angels at Home Care Services Ltd | Health & social care | 2023 |
| Angjed Ltd | Administrative & support | 2012 |
| Anje Investments Limited | Professional & scientific | 2020 |
| Ankcard Ltd | Education | 2026 |
| Ankle-Feet Orthopaedic Services Ltd | Health & social care | 2017 |
| Anna Development Limited | Professional & scientific | 2024 |
| Anna Kirby Limited | Health & social care | 2014 |
| Anson Limited | Health & social care | 2023 |
| Anstaar Limited | Health & social care | 2021 |
| Ant's Auto Mobiles (Fergie Fleet) Ltd | Transport & logistics | 2022 |
| Antarro Limited | Professional & scientific | 2025 |
| Anthology PUB & Kitchen Limited | Hospitality | 2020 |
| Anthony Hall Hairdressing Ltd | Other services | 2013 |
| Anti Average Ltd | Professional & scientific | 2011 |
| Antvision Ltd | Professional & scientific | 2023 |
| Antwerp Diamonds Limited | Wholesale & retail | 2004 |
| Anumana Limited | Information & communication | 2021 |
| Anupatel Ltd | Health & social care | 2020 |
| Anything IS Possible Group Ltd | Other services | 2023 |
| AP Inc Ltd | Health & social care | 2024 |
| AP Recruitment Outsourcing Group Bidco Limited | Administrative & support | 2025 |
| AP Recruitment Outsourcing Group Topco Limited | Administrative & support | 2025 |
| Apap Holdings Ltd | Health & social care | 2023 |
| Apartment 2 Limited | Households | 2015 |
| APB Trading Services Limited | Administrative & support | 2026 |
| APD Enterprises Ltd | Wholesale & retail | 2024 |
| APD Surgical Limited | Health & social care | 2020 |
| APE Manchester Limited | Real estate | 2020 |
| Apel Management Limited | Financial services | 2014 |
| Apex Academy Limited | Education | 2024 |
| Apex Doma Ltd | Construction | 2018 |
| Apex Gym (Staffordshire) LLP | | 2019 |
| Apex Gym Ltd | Arts & recreation | 2018 |
| Apexclimax Limited | Real estate | 2026 |
| Apexia VIP Ltd | Other services | 2026 |