| Ashfold Consulting Limited | Professional & scientific | 2017 |
| Ashleigh House Stables Limited | Real estate | 2021 |
| Ashley JAY Limited | Manufacturing | 2002 |
| Ashmore Events Ltd | Administrative & support | 2022 |
| Asiloibot Limited | Administrative & support | 2019 |
| Asima Ltd | Wholesale & retail | 2026 |
| ASK Property Group (19 Rowlands) Ltd | Construction | 2021 |
| ASK Property Investment Group Ltd | Financial services | 2021 |
| Aska Healthcare Ltd | Transport & logistics | 2015 |
| Aske Soft LAB Ltd | Information & communication | 2005 |
| Aslan Capital Ltd | Professional & scientific | 2005 |
| ASP Chauffeurs Limited | Transport & logistics | 2013 |
| Aspect Heating Solutions Ltd | Construction | 2023 |
| Aspects (Horsham) Management Limited | Households | 2001 |
| Aspire Developments U.K. Ltd | Construction | 2018 |
| Aspire Prestige Developments Ltd | Construction | 2025 |
| Aspire Southern Homes Ltd | Construction | 2022 |
| Assael Wright Architecture Ltd | Construction | 2025 |
| Asset Loans & Leasing Finance Ltd | Financial services | 2025 |
| Assethouse Limited | Real estate | 2025 |
| Associated Distribution Limited | Real estate | 2003 |
| Association for Prisoners Maintaining Innocence | Information & communication | 2025 |
| Association of British Riding Schools | Other services | 1996 |
| Association of Business Poets Ltd | Other services | 2025 |
| Assured Roofing Contractors Southern Ltd | Administrative & support | 2018 |
| Assurity Consulting Holdings Limited | Financial services | 2016 |
| Assurity Consulting Limited | Professional & scientific | 1988 |
| Asteer Consulting Ltd | Professional & scientific | 2018 |
| Astime Properties Limited | Real estate | 2010 |
| Astral Automation Limited | Information & communication | 2024 |
| Astral Group Holdings Limited | Information & communication | 2024 |
| ASW Estates Ltd | Real estate | 2019 |
| AT Home Estate Agents Ltd | Real estate | 2015 |
| Atara Golf Ltd | Manufacturing | 2025 |
| Atara Holdings Ltd | Financial services | 2025 |
| ATC Enterprises Ltd | Wholesale & retail | 2012 |
| Athena Cleaning Services Ltd | Administrative & support | 2013 |
| Athis Limited | Arts & recreation | 2002 |
| Atlantic House (Billingshurst) Management Co Ltd | Households | 2019 |
| Atlas Construction Projects Limited | Construction | 2021 |
| Atlas HPS UK Ltd | Construction | 2021 |
| ATM Industry Association, Inc. | | 2002 |
| Atmos Civils Limited | Construction | 2026 |
| Atmos Construct Ltd | Construction | 2024 |
| Atmos Group Ltd | Financial services | 2024 |
| ATO Aviation Training Organisation Ltd | Education | 2021 |
| Atoz Media Ltd | Information & communication | 2018 |
| ATP Technical Limited | Administrative & support | 2023 |
| Atraxa Digital Ltd | Information & communication | 2026 |
| Atrium Veterinary Services Limited | Professional & scientific | 2021 |
| ATS Machinery Limited | Manufacturing | 2003 |
| ATS Tree Surgeons Limited | Professional & scientific | 1992 |
| Attica Studios Limited | Manufacturing | 2022 |
| Auburn Hair and Beauty Ltd | Other services | 2022 |
| Audio Note (UK) Limited | Manufacturing | 2003 |
| Audio Tech Transport Services Ltd | Transport & logistics | 2023 |
| Audiology Plus Ltd. | Health & social care | 2017 |
| Auld Lang Signs Limited | Professional & scientific | 2024 |
| Aureon Collector Limited | Wholesale & retail | 2024 |
| Auris Solutions Ltd | Wholesale & retail | 2023 |
| Aurora Sleep Consultancy Ltd | Other services | 2023 |
| Aury Builders Limited | Construction | 2018 |
| Auslish Property Ltd | Construction | 2025 |
| Auspice Limited | Information & communication | 2018 |
| Austin Alliance Limited | Professional & scientific | 2015 |
| Authenticated by Aureon Limited | Professional & scientific | 2025 |
| Authenticq Ltd | Professional & scientific | 2008 |
| Autiprint CIC | Education | 2026 |
| Auto Team Mechanics Ltd | Wholesale & retail | 2008 |
| Autoinvest Ltd | Transport & logistics | 2015 |
| Automatic Car Wash Ltd | Wholesale & retail | 2022 |
| Automotive Trading Ltd | Wholesale & retail | 2020 |
| Automotive Woodworks Limited | Manufacturing | 2021 |
| Autoparts (UK) Limited | Wholesale & retail | 2005 |
| Autoparts Precious Metals (UK) Limited | Water & waste | 2015 |
| AV Bubble House Limited | Wholesale & retail | 2026 |
| AV Deliveries Ltd | Transport & logistics | 2025 |
| AV User Group Ltd | Professional & scientific | 2010 |
| AVA & Co UK Limited | Construction | 2020 |
| Avaj Controls Ltd | Construction | 2019 |
| Avance Aqua Ltd | Financial services | 2023 |
| Avanti Sussex Ltd | Real estate | 2024 |
| Avero Platform Ltd | Information & communication | 2025 |
| Aves Development Ltd | Construction | 2020 |
| Avesio Systems Limited | Professional & scientific | 2006 |
| Avianta Aerospace Ltd | Manufacturing | 2025 |
| Aviation Insider Ltd | Information & communication | 2016 |
| Aviation Safety Consultants Limited | Professional & scientific | 2018 |
| Aviation Training Solutions Ltd | Professional & scientific | 2011 |
| Avid Healthcare Consultancy Ltd | Health & social care | 2022 |
| Avmarine Limited | Transport & logistics | 2002 |
| AVN Fitness Ltd | Health & social care | 2012 |
| Avon Dynamics Ltd | Manufacturing | 2025 |
| Avonbird Ltd | Real estate | 2017 |
| AW Accountancy and Tax Limited | Professional & scientific | 2024 |
| AW Contracting Services Ltd | Agriculture & fishing | 2025 |
| AW Electrical (Sussex) Ltd | Construction | 2014 |
| AWL Occupational Health Ltd | Health & social care | 2010 |
| Axevara Holdings Ltd | Financial services | 2026 |
| Axevara Medical Ltd | Wholesale & retail | 2026 |