| Anki Global Limited | Wholesale & retail | 2024 |
| Anniko Holdings Limited | Real estate | 2010 |
| Anodos Associates Limited | Professional & scientific | 1998 |
| Anodos Discovery Limited | Professional & scientific | 2000 |
| Anscombe and Ringland Limited | Real estate | 1971 |
| Ansell Land Services Ltd | Administrative & support | 2016 |
| ANT Talent Ltd | Administrative & support | 2023 |
| Anthony Millard Limited | Professional & scientific | 2019 |
| Antonio Cooper Consulting Ltd | Construction | 2023 |
| Antsar Investments Ltd | Real estate | 2023 |
| Anudip Ltd | Real estate | 2026 |
| AO Carpentry Limited | Construction | 2019 |
| AOC Associates Ltd | Construction | 2015 |
| Aone Solns Limited | Wholesale & retail | 2025 |
| AOP Title Limited | Professional & scientific | 2001 |
| AP Thompson Limited | Professional & scientific | 2015 |
| Apeiron Property Group Ltd | Real estate | 2025 |
| Apex Cars Limited | Wholesale & retail | 2019 |
| Apex Drive Management Limited | Households | 1982 |
| Apex Passive Fire Protection Ltd | Construction | 2014 |
| APK Contractors Limited | Mining & quarrying | 2021 |
| Apohli Limited | Manufacturing | 2025 |
| Appappit Ltd | Extraterritorial | 2015 |
| Apple Homes Limited | Extraterritorial | 2004 |
| Apple Nails Camberley Ltd | Other services | 2022 |
| Appliance Homecare Ltd | Administrative & support | 2017 |
| Applico Limited | Information & communication | 2023 |
| Applied Neuroscience Solutions Limited | Professional & scientific | 2010 |
| Applied Space Solutions Limited | Administrative & support | 2017 |
| Apply Recruitment Ltd | Administrative & support | 2016 |
| Apricus Consultants Ltd | Professional & scientific | 2015 |
| April Quest Limited | Administrative & support | 2019 |
| Apthorp Asbestos Management Ltd | Professional & scientific | 2024 |
| Aqsa & Co Limited | Information & communication | 2011 |
| Aqua Design Landscaping Limited | Professional & scientific | 2024 |
| Aqua Infrastructure Limited | Real estate | 2008 |
| Aqualux Renovations Ltd | Construction | 2024 |
| Aquamagic Plumbing and Heating Limited | Construction | 2023 |
| Aquarius Water Solutions Limited | Administrative & support | 2011 |
| Aquila Traders Limited | Wholesale & retail | 2019 |
| AR Financial Management Ltd | Professional & scientific | 2017 |
| AR2 Medical Limited | Health & social care | 2021 |
| AR2 Properties Limited | Real estate | 2021 |
| AR4 Ltd | Administrative & support | 2026 |
| Aragon House Property Management Company Limited | Households | 2004 |
| Aragon Place Management Company Limited | Households | 1994 |
| ARC Construction Consultants Ltd. | Construction | 2008 |
| Arch First Ltd | Information & communication | 2025 |
| Archerfields Limited | Real estate | 2019 |
| Archinterio Limited | Professional & scientific | 2007 |
| Arctic Access Limited | Construction | 2019 |
| Arcus Landscaping Ltd | Administrative & support | 2016 |
| Arcus Universe Limited | Information & communication | 2014 |
| Ardmore Search Partners Limited | Professional & scientific | 2018 |
| ARE Apps Ltd | Information & communication | 2011 |
| Arghans Investments Limited | Real estate | 2004 |
| Aria Catering Limited | Hospitality | 2013 |
| Aries Consulting Ltd | Information & communication | 2015 |
| Aries Ecotech Solutions Ltd | Construction | 2025 |
| Arisone Ltd | Construction | 2018 |
| Aristo Ltd | Professional & scientific | 2021 |
| ARK Group Services Ltd | Construction | 2006 |
| ARK Holding Corporation Ltd | Financial services | 2025 |
| ARK INVEST2 Ltd | Real estate | 2025 |
| ARK Residential Properties Ltd | Real estate | 2014 |
| ARK Trading and Technologies Limited | Administrative & support | 2012 |
| Arko London Ltd | Administrative & support | 2011 |
| Armd Holdings Limited | Professional & scientific | 2016 |
| Armstrong Whitworth Aircraft Limited | Extraterritorial | 1996 |
| ARO Property Services Limited | Real estate | 2023 |
| Around the Clock Care Agency Ltd. | Health & social care | 2016 |
| Arrow Construction Limited | Construction | 2020 |
| Art & Design Productions Limited | Professional & scientific | 1998 |
| Art of PDR Ltd | Wholesale & retail | 2020 |
| Art of the Possible Coaching Ltd | Other services | 2017 |
| Arteco Designs Limited | Manufacturing | 2012 |
| Arthashree Properties Ltd | Construction | 2025 |
| Arthur Mitchell Limited | Agriculture & fishing | 1955 |
| Artifeks Limited | Administrative & support | 2018 |
| Artisan Spoon Ltd | Hospitality | 2025 |
| Aryan Associates Limited | Health & social care | 2008 |
| Aryana EXP Ltd | Wholesale & retail | 2025 |
| Asahi Holdings Limited | Real estate | 2017 |
| Asaport Limited | Health & social care | 2023 |
| Asclepius OHS Limited | Health & social care | 2013 |
| Ascot Group (UK) Limited | Wholesale & retail | 1996 |
| Asctech Ltd. | Information & communication | 2006 |
| Asdw Ltd | Hospitality | 2020 |
| Asees Traders Ltd | Manufacturing | 2023 |
| ASH Lodge Drive (ASH) Management Company Limited | Households | 2018 |
| ASH Mews (ASH) Management Company Limited | Households | 2001 |
| ASH Vale MOT Ltd | Wholesale & retail | 2025 |
| Ashbury 1959 Limited | Extraterritorial | 2016 |
| Ashbury Lloyd Group Ltd | Professional & scientific | 2023 |
| Ashdale Trading Limited | Real estate | 2003 |
| Ashford GG Ltd | Wholesale & retail | 2025 |
| Ashford Hill NO.2 Management Company Limited | Households | 2023 |
| Ashland Carpentry Services Limited | Construction | 2016 |
| Ashmont Group Ltd | Administrative & support | 2025 |
| Ashmont Nexus Ltd | Administrative & support | 2025 |