| AGM Brickwork & Construction Limited | Construction | 2024 |
| AGM Transport Ltd | Administrative & support | 2017 |
| Agma Network Ltd | Wholesale & retail | 2020 |
| Agnana Trans Ltd | Transport & logistics | 2024 |
| Agnostic Projects Limited | Professional & scientific | 2024 |
| Agora 3 Ltd | Information & communication | 2019 |
| Agora Heart Limited | Health & social care | 2019 |
| AGR Media Group Ltd | Administrative & support | 2015 |
| Agrasav Limited | Real estate | 1994 |
| Agri-Maintenance Limited | Manufacturing | 2013 |
| Agricola Court Management Company Limited | Households | 1977 |
| Agricultural Planning Engineering Construction Services Limited | Extraterritorial | 2020 |
| Agrigenics Ltd. | Manufacturing | 2019 |
| Agrivoltaics Ltd | Extraterritorial | 2020 |
| AGS Compliance Ltd | Professional & scientific | 2022 |
| AGW Landscapes Ltd | Administrative & support | 2024 |
| AH Hospitality Limited | Hospitality | 2024 |
| AHC Cleaners Ltd | Extraterritorial | 2025 |
| Ahco Resources Limited | Financial services | 2023 |
| Ahedi Construction Hampshire Ltd | Households | 2025 |
| AHJ Couriers Ltd | Transport & logistics | 2022 |
| AHL Global Limited | Wholesale & retail | 2014 |
| Ahliyah's Beautique Ltd | Other services | 2019 |
| AHM Engineering Services Ltd | Manufacturing | 2025 |
| Ahmed Brothers Investments Ltd | Real estate | 2019 |
| Ahmed Corporation Limited | Other services | 2017 |
| Ahmed Driving Academy Ltd | Education | 2024 |
| Ahmed Property Investments (Southampton) LLP | | 2022 |
| Ahmen Ltd | Construction | 2026 |
| Ahna Holdings Limited | Professional & scientific | 2022 |
| Ahpc Solutions Limited | Wholesale & retail | 2025 |
| AI PI DI Transport Ltd | Transport & logistics | 2021 |
| AI Plumbing and Heating Southampton Limited | Construction | 2023 |
| AIC Heating and Plumbing Services Ltd | Construction | 2024 |
| Aich Nine Ltd | Financial services | 2026 |
| Aiden's Bar Limited | Financial services | 2020 |
| Aidotech Ltd | Information & communication | 2015 |
| AIG Logistics Ltd | Transport & logistics | 2025 |
| Aihua Catering Limited | Hospitality | 2024 |
| AIJ Electrics Limited | Construction | 2014 |
| Aika Lauren Limited | Health & social care | 2022 |
| Aila Images Limited | Information & communication | 2015 |
| Ailab (Artificial Intelligence Laboratory) Limited | Professional & scientific | 2023 |
| AIM 2 Entertain Ltd | Wholesale & retail | 2018 |
| AIM Building & Construction Ltd | Construction | 2025 |
| AIM CAD Solutions Limited | Professional & scientific | 2020 |
| AIM Publishing Ltd | Professional & scientific | 2025 |
| Aima Fostering Limited | Health & social care | 2025 |
| Aimac Construction Limited | Construction | 2025 |
| Aimybiz Ltd | Information & communication | 2025 |
| Ainyfit Limited | Arts & recreation | 2015 |
| Aion Kairos Ltd | Real estate | 2023 |
| Air 2 Heat Renewable Energy Ltd | Construction | 2022 |
| Air Andy’S Industrial Roofing Ltd | Construction | 2026 |
| Air Conditioning Services (South) Limited | Construction | 2010 |
| Air Cool Mechanical Services Ltd | Construction | 2018 |
| Air Craft (Southern) Ltd | Professional & scientific | 2010 |
| Air Holiday UK Ltd | Administrative & support | 2025 |
| Air Restore Ltd | Wholesale & retail | 2023 |
| Air Tech Testing Limited | Real estate | 2007 |
| AIR2PORT Southampton Limited | Transport & logistics | 2022 |
| Airbridge Networks Ltd | Transport & logistics | 2010 |
| Aircontrol Southern Ltd | Manufacturing | 2013 |
| Aircraft Technical Management Limited | Manufacturing | 2002 |
| Airpole Limited | Administrative & support | 2017 |
| Airport Energy Limited | Transport & logistics | 1999 |
| Airport Energy Services Limited | Transport & logistics | 2003 |
| Airssociates Consulting Limited | Professional & scientific | 2017 |
| Airwave Europe Ltd. | Administrative & support | 1994 |
| Airwaves Media Productions Ltd | Manufacturing | 1987 |
| AIS Synergy Group Limited | Transport & logistics | 2013 |
| Aisense Marketing Ltd | Professional & scientific | 2025 |
| Aisha Sangar Ltd | Hospitality | 2026 |
| Aiuk Life Ltd | Real estate | 2016 |
| AJ & Daughters Roofing Ltd | Manufacturing | 2026 |
| AJ & MG Company Limited | Arts & recreation | 2003 |
| AJ Builder Service Ltd | Construction | 2026 |
| AJ Electrical (Southampton) Limited | Construction | 2016 |
| AJ Gifts Limited | Wholesale & retail | 2014 |
| AJ Holdings (DK) Ltd | Professional & scientific | 2022 |
| AJ Housing Solutions Ltd | Real estate | 2024 |
| AJ Marine Services Ltd | Manufacturing | 2023 |
| Ajab Entertainment Inc Limited | Health & social care | 2016 |
| Ajaxtem Limited | Health & social care | 2025 |
| Ajay IT Consulting Ltd | Information & communication | 2017 |
| Ajay Trading Limited | Wholesale & retail | 2000 |
| AJB Mechanical Services Limited | Construction | 2016 |
| AJC Assessments Limited | Health & social care | 2006 |
| Ajcc Properties Ltd | Financial services | 2022 |
| AJG Project Management Limited | Professional & scientific | 2015 |
| AJJ Welding and Fabrication Ltd | Manufacturing | 2022 |
| AJK Cooper Limited | Wholesale & retail | 2022 |
| AJM Bespoke Builds Ltd | Construction | 2022 |
| AJM Composites Ltd | Manufacturing | 2019 |
| AJM Material Salvage Limited | Wholesale & retail | 2018 |
| AJM Trans Limited | Transport & logistics | 2019 |
| Ajmt Services Ltd | Administrative & support | 2023 |
| AJP Technical Limited | Information & communication | 2007 |
| AJS Facility Services Ltd | Administrative & support | 2026 |
| Ajuni Sandhu Ltd | Transport & logistics | 2024 |