| Ahead 3000 Limited | Administrative & support | 2006 |
| Ahmadovs Company Ltd | Wholesale & retail | 2025 |
| Ahmed Alhadhrami Limited | Wholesale & retail | 2025 |
| AHR Consulting Limited | Information & communication | 2014 |
| Ahsan Kabir Ltd | Wholesale & retail | 2025 |
| AHW Group Ltd | Wholesale & retail | 2023 |
| AI Nexus Labs Ltd | Information & communication | 2024 |
| AI Ready Ltd | Information & communication | 2023 |
| AI1GROUP Limited | Wholesale & retail | 2025 |
| AI71 Ltd | Professional & scientific | 2025 |
| Aiam Trading Ltd | Wholesale & retail | 2025 |
| AIB Limited | Wholesale & retail | 2025 |
| Aiba Business Solutions Ltd | Information & communication | 2024 |
| Aicw Limited | Information & communication | 2024 |
| Aidyl Ltd | Wholesale & retail | 2023 |
| Aikoniq Health Ltd | Information & communication | 2024 |
| AIM High Hosting Ltd | Information & communication | 2023 |
| AIM Higher Canine Services Limited | Other services | 2021 |
| Aimlord Properties Limited | Households | 1989 |
| Aims for Life - Coaching for Disabled People Community Interest Company | Education | 2024 |
| Aimseytv Ltd | Information & communication | 2022 |
| Aimyable Ltd | Information & communication | 2024 |
| Aipfm Limited | Information & communication | 2026 |
| Aipresso Limited | Information & communication | 2025 |
| Air & Power Services Ltd | Manufacturing | 2002 |
| Air Craft Media Ltd | Administrative & support | 2013 |
| Air-Site Ltd | Construction | 2006 |
| Aira Transport Ltd | Transport & logistics | 2026 |
| Airbourne Limited | Information & communication | 2015 |
| Aircraft Graphics Ltd | Professional & scientific | 2020 |
| Aircury Ltd | Information & communication | 2017 |
| Airdata Limited | Professional & scientific | 2020 |
| Airflow Ventilation Contractors Limited | Construction | 2018 |
| Airoil-Flaregas Limited | Extraterritorial | 1980 |
| Airplus Technologies Ltd | Manufacturing | 2025 |
| Airport Executive Cars (Dorset) Ltd | Transport & logistics | 2012 |
| Airtek FAN Solutions Limited | Manufacturing | 2004 |
| Airwaves (South Coast) Limited | Information & communication | 1994 |
| Aish Electro-Mechanical Services Limited | Professional & scientific | 2004 |
| Aish Technologies Limited | Manufacturing | 2000 |
| Aisisted Ltd | Information & communication | 2022 |
| AIT Umbrella Limited | Professional & scientific | 2017 |
| Aitchison Agri UK Limited | Administrative & support | 2017 |
| Aiverde Ltd | Information & communication | 2025 |
| Aivery Ltd | Information & communication | 2025 |
| Aivs Software Limited | Administrative & support | 2024 |
| AJ & ABQ Ltd | Other services | 2021 |
| AJ Developments (Cannon Street) Ltd | Construction | 2019 |
| AJ Developments (North Road) Ltd | Construction | 2018 |
| AJ Developments (Riviera) Ltd | Construction | 2021 |
| AJ Developments (Sloop) Ltd | Real estate | 2021 |
| AJ Developments (Wainsford Two) Limited | Construction | 2023 |
| AJ Developments (West Quay) Limited | Construction | 2018 |
| AJ Developments (Wimborne Road) Limited | Real estate | 2019 |
| AJ Enterprises (Salisbury) Ltd | Wholesale & retail | 2012 |
| AJ Island Hospitality Ltd | Hospitality | 2025 |
| AJ Land Consultancy Limited | Other services | 2017 |
| AJ Property Group Limited | Financial services | 2017 |
| AJ Property Management (South) Limited | Real estate | 2016 |
| AJ Sebastian Ltd | Health & social care | 2024 |
| AJB Dynamics Ltd | Wholesale & retail | 2025 |
| AJC Developments (South) Limited | Other services | 2018 |
| AJC Homes Limited | Construction | 2017 |
| AJC Land Consultancy Ltd | Real estate | 2022 |
| AJL 1 Ltd | Construction | 2023 |
| AJL Capital Limited | Wholesale & retail | 2021 |
| AJL Cleaning Limited | Administrative & support | 2005 |
| AJL Ecom Limited | Wholesale & retail | 2024 |
| AJL Guardian Training and Safety Ltd | Professional & scientific | 2025 |
| AJM IT Solutions Limited | Information & communication | 2012 |
| AJM Utilities Ltd | Energy | 2018 |
| AJN Project Solutions Ltd | Professional & scientific | 2023 |
| AJS Financial Planning Limited | Professional & scientific | 2012 |
| AJS Operating Company Ltd | Information & communication | 2018 |
| AJS Wessex Holdings Limited | Financial services | 2026 |
| AJT Decorators Ltd | Construction | 2015 |
| AJU Group Ltd | Financial services | 2017 |
| AJU Motorsport Ltd | Professional & scientific | 2015 |
| AJW Consultants Ltd | Professional & scientific | 2018 |
| AJY Consulting Ltd | Information & communication | 2021 |
| AJY Project Management Consultancy Ltd | Professional & scientific | 2024 |
| AK & KK Medical Ltd | Health & social care | 2024 |
| AK Academy of Dancing Ltd | Real estate | 2022 |
| AK Investments Group Limited | Health & social care | 2017 |
| AK Pangeni Properties Limited | Real estate | 2025 |
| AK Wellness Limited | Other services | 2020 |
| AKA Combat Sports CIC | Education | 2023 |
| Akai Juices and Bowls Ltd | Hospitality | 2022 |
| Akbar Takeaway Limited | Hospitality | 2026 |
| Akciri Ltd | Hospitality | 2026 |
| Aksanaz Ltd | Hospitality | 2026 |
| Aktius Ltd | Professional & scientific | 2013 |
| AL Hafiz Limited | Wholesale & retail | 2025 |
| AL Innovation Solutions Ltd | Information & communication | 2025 |
| AL NUR Care Homes Ltd | Health & social care | 2025 |
| AL Signature Drainage Ltd | Water & waste | 2025 |
| AL Tamam Company Ltd | Wholesale & retail | 2025 |
| AL Thermo Ltd | Construction | 2017 |
| AL Windows Ltd | Manufacturing | 2018 |
| Al-Baraa Al-Siyabi Limited | Wholesale & retail | 2025 |