| Ashton Keynes Management Company Limited | Households | 2024 |
| Ashton-Yair Consulting Limited | Information & communication | 2005 |
| Ashtone Electrical Services Limited | Construction | 2011 |
| ASJ Direct Ltd | Wholesale & retail | 2023 |
| Asjh Data Limited | Information & communication | 2018 |
| ASK 4 Construction Ltd | Construction | 2017 |
| Asma Muneer Limited | Other services | 2023 |
| ASP Digital Limited | Professional & scientific | 2021 |
| Aspect Solutions Group Ltd | Professional & scientific | 2021 |
| Aspenmaple Ltd | Professional & scientific | 2016 |
| Aspihre Group Limited | Information & communication | 2018 |
| Aspired Care Ltd | Health & social care | 2024 |
| Assertive Infosec Solutions Limited | Information & communication | 2026 |
| Asset Office Interiors Ltd | Construction | 2018 |
| ASSIST4BIZ Ltd | Professional & scientific | 2013 |
| Associated Property Limited | Real estate | 1994 |
| Assured Living Solutions Limited | Real estate | 2022 |
| Aster Legacy Ltd | Manufacturing | 2025 |
| Astons Sales & Lettings Limited | Real estate | 2004 |
| Astute Copy Ltd | Professional & scientific | 2025 |
| AT Design & Build Ltd | Construction | 2021 |
| AT the ARK Limited | Wholesale & retail | 2012 |
| Ataraxy Wellbeing Ltd | Health & social care | 2023 |
| ATB Support Ltd | Professional & scientific | 2009 |
| ATC Equities Limited | Real estate | 2019 |
| ATC Scaffolding Supplies Limited | Construction | 2014 |
| Atherton Place Management Company Limited | Households | 2022 |
| Atherton Stone Limited | Administrative & support | 2012 |
| Athlete Performance LAB Limited | Education | 2025 |
| Athlix Staffing Ltd | Administrative & support | 2026 |
| Atlantic Business Services Limited | Information & communication | 2002 |
| Atlas Services London Ltd | Wholesale & retail | 2025 |
| Atlk Limited | Construction | 2024 |
| Atma Properties Ltd | Real estate | 2020 |
| Atma Property Management Ltd | Real estate | 2023 |
| Atomic Dental LAB Ltd | Manufacturing | 2021 |
| Atrytone Creations Ltd | Manufacturing | 2026 |
| Atrytone Group Ltd | Financial services | 2026 |
| Attalus Investments Ltd | Financial services | 2019 |
| Aubilities Ltd | Information & communication | 2020 |
| Auction House West Yorkshire Limited | Administrative & support | 2009 |
| Audio OIL Ltd | Information & communication | 2022 |
| August Contractors Limited | Wholesale & retail | 2019 |
| Aunty UK Wali Limited | Hospitality | 2026 |
| Aurelius Pharma Consulting Limited | Professional & scientific | 2024 |
| Aureus Ventures Ltd | Professional & scientific | 2020 |
| Auriol Limited | Administrative & support | 2001 |
| Auto MAN Ltd | Other services | 2022 |
| Autoguard Automotive Solutions Limited | Extraterritorial | 2021 |
| Autoguard Group Limited | Financial services | 2021 |
| Autoguard Holdings Limited | Financial services | 2026 |
| Autoguard Services Ltd | Administrative & support | 2024 |
| Autoguard Warranties Ltd | Financial services | 2008 |
| Automarc Services Limited | Wholesale & retail | 2010 |
| Automatax Ltd | Wholesale & retail | 2026 |
| Automotive Support Services Limited | Extraterritorial | 2026 |
| Automotive Support Solutions Limited | Wholesale & retail | 2026 |
| Automotive Venture Ltd | Water & waste | 2024 |
| Autopilot Systems AI Ltd | Information & communication | 2025 |
| Autopour Limited | Manufacturing | 2023 |
| Autotech Southern Limited | Wholesale & retail | 2011 |
| AUX Commercial Air Conditioners Limited | Wholesale & retail | 2024 |
| Available 247 Ltd | Extraterritorial | 2022 |
| Avalon Client Services Ltd | Professional & scientific | 2017 |
| Avalon Invest Limited | Real estate | 2014 |
| AVC Title Bali Limited | Professional & scientific | 2011 |
| AVC Title Bangkok Limited | Professional & scientific | 2011 |
| AVC Title Chiang MAI NO. 4 Limited | Professional & scientific | 2016 |
| AVC Title Chiang MAI NO.1 Limited | Professional & scientific | 2015 |
| AVC Title Chiang MAI NO.2 Limited | Professional & scientific | 2015 |
| AVC Title Chiang MAI NO.3 Limited | Professional & scientific | 2016 |
| AVC Title China Limited | Professional & scientific | 2013 |
| AVC Title HUA HIN Limited | Professional & scientific | 2023 |
| AVC Title Japan Limited | Professional & scientific | 2026 |
| AVC Title Khao LAK Limited | Professional & scientific | 2022 |
| AVC Title New Zealand Limited | Professional & scientific | 2011 |
| AVC Title Phuket Limited | Professional & scientific | 2010 |
| AVC Title Samui Limited | Professional & scientific | 2010 |
| Avello Limited | Professional & scientific | 2009 |
| AVENUE110 Ltd | Wholesale & retail | 2025 |
| Avenues Care Ltd | Health & social care | 2019 |
| Aver Communication Limited | Professional & scientific | 2011 |
| Avicor Ltd | Administrative & support | 2020 |
| Avncis Ltd | Information & communication | 2021 |
| Avocor Limited | Other services | 2000 |
| Avro International Aerospace Limited | Extraterritorial | 1992 |
| Avyukt PMO Solutions Limited | Information & communication | 2013 |
| AW Wood Flooring Ltd | Construction | 2026 |
| Awch Group Limited | Energy | 2024 |
| Awesome Hives Ltd | Wholesale & retail | 2025 |
| AWL Landscapes Limited | Administrative & support | 2014 |
| Axaris IP Limited | Information & communication | 2025 |
| Axinte Trans Ltd | Transport & logistics | 2022 |
| Axjan Limited | Professional & scientific | 2021 |
| AXS IT Solutions Ltd | Information & communication | 2016 |
| Axxess 28 Limited | Construction | 1991 |
| AY International Management Limited | Wholesale & retail | 2024 |
| AY Panaga Medical Limited | Health & social care | 2025 |
| AYR Aesthetics Limited | Health & social care | 2022 |
| Ayton-Smith Limited | Construction | 2023 |