| Aldis-Hobbs Ltd | Construction | 2018 |
| Aldsworth Farm Limited | Agriculture & fishing | 2007 |
| Aldwick Doors & Windows Limited | Administrative & support | 2006 |
| Aldwick Services Limited | Arts & recreation | 2018 |
| Alehouse Brasseries Limited | Hospitality | 2018 |
| Aletheia (Bognor Regis) Ltd | Wholesale & retail | 2024 |
| Alford Electrical Engineering Ltd | Construction | 2005 |
| Algea Group Ltd | Financial services | 2023 |
| Alien Bloodvision Limited | Arts & recreation | 2025 |
| Aligned Group Ltd | Wholesale & retail | 2019 |
| Aligned Projects Consulting Ltd | Professional & scientific | 2025 |
| Alisara Investments Limited | Real estate | 2022 |
| Alison Hone Limited | Professional & scientific | 2020 |
| ALL Asbestos Environmental Ltd | Construction | 2025 |
| ALL Asbestos Limited | Construction | 2020 |
| ALL Coin Ltd | Arts & recreation | 2005 |
| ALL in the Box Limited | Wholesale & retail | 2021 |
| ALL Porsche Racing Ltd | Arts & recreation | 2025 |
| ALL Sussex Cars Ltd | Transport & logistics | 2025 |
| Allbright Proclean Ltd | Administrative & support | 2026 |
| Allclimates Limited | Energy | 2014 |
| Allday Apps Ltd | Information & communication | 2014 |
| Allen Dawson Ltd | Wholesale & retail | 2018 |
| Allen's Yard Ltd | Administrative & support | 2025 |
| Allendene Limited | Professional & scientific | 2008 |
| Allentown UK Limited | Administrative & support | 2004 |
| Allout Solutions Limited | Professional & scientific | 2022 |
| Allsop & Francis Ltd | Wholesale & retail | 1991 |
| Almighty Brands Limited | Professional & scientific | 2008 |
| Almodington Meadow Ltd | Households | 2023 |
| Almond Tree Homes Ltd | Real estate | 2017 |
| Alongside YOU | Health & social care | 2009 |
| Alonsoebert Ltd | Real estate | 2022 |
| Alpe Holdings Ltd | Financial services | 2022 |
| Alpe Properties Ltd | Real estate | 2022 |
| Alpenrose Ltd | Professional & scientific | 2020 |
| Alpha Communities | Education | 2001 |
| Alpha Investments (Southern) Ltd | Real estate | 2004 |
| Alpha Yachting Limited | Administrative & support | 2003 |
| Alpine Adventure Holidays Ltd | Administrative & support | 2019 |
| Alternative Contract Solutions Limited | Professional & scientific | 1977 |
| Alternative Means Limited | Health & social care | 2000 |
| Altior Developments Limited | Construction | 2020 |
| Alts Advisers Ltd | Professional & scientific | 2023 |
| Alzaidi Property Company Limited | Real estate | 2017 |
| Alzaidi UK Limited | Real estate | 2017 |
| AM Design Ltd | Professional & scientific | 2009 |
| AM Mobile Ltd | Other services | 2015 |
| AM Precision Accounting Ltd | Professional & scientific | 2026 |
| Amalo Consulting Ltd | Professional & scientific | 2013 |
| Amanda Wilsher Associates Ltd | Professional & scientific | 2014 |
| Amannpreet Singh Ltd | Professional & scientific | 2015 |
| Ambassador Building Company Southern Limited | Construction | 2025 |
| Amber Scaffolding (Holdings) Limited | Extraterritorial | 2018 |
| Amberley Boarding Ltd | Other services | 2020 |
| Amberley Shop Properties Ltd. | Real estate | 1998 |
| Ambient Associates Limited | Professional & scientific | 2004 |
| Ambush Pest Control Limited | Administrative & support | 2002 |
| Amchella Events and Sleepovers Ltd | Other services | 2019 |
| Amelia Court Property Maintenance Ltd | Households | 2006 |
| Amelia Developments Limited | Real estate | 2013 |
| Amelia Hillman Interiors Ltd | Professional & scientific | 2024 |
| Amelia Properties Ltd | Real estate | 2004 |
| AMG Actuators Limited | Manufacturing | 2002 |
| AMG Financial UK Ltd | Professional & scientific | 2013 |
| AMG Investment Holdings Ltd | Financial services | 2015 |
| AMG Real Estate Ltd | Real estate | 2018 |
| AMJ Care Ltd | Health & social care | 2013 |
| Ammonite Design Ltd | Construction | 2015 |
| AMS Aircraft Services Limited | Transport & logistics | 2015 |
| AMS Automation Management Services Ltd | Professional & scientific | 2021 |
| AMS Contracting Limited | Agriculture & fishing | 2011 |
| AMS Maintenance Services Limited | Construction | 2014 |
| AMS Masonry Ltd | Professional & scientific | 2024 |
| AMS Plant Limited | Administrative & support | 2020 |
| Amshall Ltd | Administrative & support | 2024 |
| AMY Berry Limited | Professional & scientific | 2014 |
| Amylou Limited | Information & communication | 2004 |
| Amystoddardajayi Ltd | Health & social care | 2022 |
| Ananta Kranti Foundations Limited | Health & social care | 2026 |
| Anderson Oak Designs Ltd | Construction | 2014 |
| Andrea Verenini Ltd | Professional & scientific | 2019 |
| Andreea Dumitrescu Limited | Health & social care | 2015 |
| Andrew Shepherd Electrics Limited | Construction | 2020 |
| Andsurgeons Ltd | Health & social care | 2025 |
| Andy Lane Agricultural Services Ltd | Wholesale & retail | 2022 |
| Andy Minard Electrical Services Limited | Construction | 2014 |
| Andy Mulligan Books Limited | Arts & recreation | 2012 |
| Andy Stedman Design Ltd | Professional & scientific | 2019 |
| Anetrex Service Mediator Ltd | Administrative & support | 2010 |
| Angel Bridal Limited | Wholesale & retail | 2022 |
| Angel Hotel Car Park Limited | Construction | 2017 |
| Angel Hotel Freehold Limited | Construction | 2017 |
| Angel Hotel Trading Limited | Hospitality | 2017 |
| Angela Roberts Property Investments Limited | Real estate | 2017 |
| Anglo-Asia Trading Ltd | Wholesale & retail | 2018 |
| Anguiera Ltd | Professional & scientific | 2024 |
| Angus Info Associates Ltd | Information & communication | 2018 |
| Anjon Limited | Professional & scientific | 1990 |
| ANN Bullen Associates Limited | Professional & scientific | 2005 |