| Atlantic Wharf (Wapping) Freehold Limited | Households | 2015 |
| Atlantic Wharf Property Management Company Limited | Households | 1995 |
| Atlas Stone Holdings Ltd | Real estate | 2026 |
| Atlascore Racing Ltd | Arts & recreation | 2025 |
| ATM Cleaning Limited | Other services | 2018 |
| Atom Facilities Ltd | Hospitality | 2008 |
| ATOMIC80 Limited | Wholesale & retail | 2010 |
| Atozsmiles Limited | Health & social care | 2022 |
| ATS Steam Cleaning Ltd | Administrative & support | 2012 |
| Auckland Manufacturing Ltd | Manufacturing | 2013 |
| Audeovox Ltd | Professional & scientific | 2023 |
| Audience Wonderland Productions Ltd | Information & communication | 2018 |
| Audio Envoy Ltd | Wholesale & retail | 2024 |
| Audiomagician Ltd | Information & communication | 2014 |
| Audioset Ltd | Manufacturing | 2011 |
| Augustine Travels Ltd | Administrative & support | 2021 |
| Augustines Property Limited | Real estate | 2018 |
| Aura Glow Salon Ltd | Other services | 2025 |
| Aurexon Limited | Wholesale & retail | 2025 |
| Aurore Belle Ltd | Other services | 2021 |
| Aurum Stays Ltd | Real estate | 2026 |
| Aurumxline Limited | Professional & scientific | 2018 |
| Aust Application Architecture Ltd | Information & communication | 2026 |
| Authentic Education Consultancy Services Limited | Education | 2016 |
| Autifony Alpha Limited | Professional & scientific | 2019 |
| Autifony Therapeutics Limited | Professional & scientific | 2011 |
| Auto Boss Service Centre Ltd | Wholesale & retail | 2020 |
| Auto Dealer Dennis Ltd | Wholesale & retail | 2015 |
| Auto Electrical Herts Limited | Construction | 2016 |
| Auto Master Stevenage Ltd | Wholesale & retail | 2015 |
| Autobella Limited | Wholesale & retail | 2014 |
| Automike Ltd | Wholesale & retail | 2024 |
| Autophix Recovery Limited | Transport & logistics | 2022 |
| Autotrace Limited | Wholesale & retail | 1987 |
| Autowise Tyre and Autocentres Limited | Wholesale & retail | 1995 |
| AV Consult Ltd | Wholesale & retail | 2017 |
| AV Holdco Ltd | Financial services | 2025 |
| AV Living Ltd | Real estate | 2020 |
| AV Property Ventures Ltd | Real estate | 2025 |
| AVA Football Academy London Ltd | Arts & recreation | 2018 |
| Avalon Consultancy Services Limited | Professional & scientific | 1996 |
| Avampa Limited | Professional & scientific | 2020 |
| Avanti Lettings Ltd | Real estate | 2024 |
| Avaron Rigging Limited | Construction | 2025 |
| AVC Sports 2024 Ltd | Arts & recreation | 2024 |
| Avcore Services Ltd. | Professional & scientific | 2015 |
| Avelix Limited | Real estate | 2016 |
| AVI Partners Ltd | Transport & logistics | 2026 |
| Avira Group Ltd | Other services | 2022 |
| Avista Plumbing & Heating Limited | Construction | 2008 |
| AVM Medical Limited | Health & social care | 2016 |
| Avmac Associates Ltd | Professional & scientific | 2019 |
| Avnet (Holdings) Ltd | Professional & scientific | 1989 |
| Avnet Bidco Limited | Professional & scientific | 2016 |
| Avnet Holdings UK Limited | Administrative & support | 2005 |
| Avnet International Holdings UK Limited | Extraterritorial | 2018 |
| Avonmouth Road Management Company Limited | Households | 2005 |
| Avrion Limited | Information & communication | 2018 |
| AVS Partners Limited | Real estate | 2007 |
| AVS Property Holdings Limited | Real estate | 2017 |
| AVS VAT Consultancy Limited | Professional & scientific | 2012 |
| AVS VAT Limited | Extraterritorial | 2006 |
| AVT of Benington Ltd | Transport & logistics | 2022 |
| Award Promotions Limited | Wholesale & retail | 2007 |
| AWB Estates Holdings Limited | Real estate | 2025 |
| AWB Group Holdings Limited | Financial services | 2025 |
| AWC Carpentry Ltd | Construction | 2024 |
| AWG Accountancy Services Limited | Professional & scientific | 2025 |
| Awkn. Ltd | Manufacturing | 2025 |
| Awridian Ltd | Professional & scientific | 2011 |
| AXB Consultancy Services Limited | Information & communication | 2009 |
| AXE Capital Group Limited | Other services | 2019 |
| Axel Interiors Ltd | Construction | 2017 |
| Axiom Initiatives Limited | Extraterritorial | 2024 |
| Axiom Offshore Ltd | Professional & scientific | 2026 |
| Axiom Parasol Global Services Ltd | Real estate | 2020 |
| Axium Networks Limited | Information & communication | 2024 |
| Axon Composites Ltd | Manufacturing | 2026 |
| Ayelle Holdings Limited | Financial services | 2025 |
| Ayelle Photography Limited | Professional & scientific | 2020 |
| Ayelle Properties Limited | Real estate | 2025 |
| Ayelle Video Limited | Information & communication | 2021 |
| Ayka Creations Ltd | Wholesale & retail | 2022 |
| Ayomiji Consults Ltd | Health & social care | 2015 |
| Ayot Consultancy Limited | Administrative & support | 2012 |
| Ayoub Homes Ltd | Real estate | 2024 |
| Aythorpe Sporting Ltd | Arts & recreation | 2025 |
| Ayurveda Medical Limited | Health & social care | 2025 |
| AZ Elite Barbers Ltd | Other services | 2026 |
| AZ Swan Express Ltd | Transport & logistics | 2025 |
| Azuchi UK Limited | Health & social care | 2025 |
| Azureblu Limited | Financial services | 2017 |
| Azuri Car Care Ltd | Wholesale & retail | 2017 |
| Azuri Window Films Ltd | Construction | 2026 |
| B & B Healthcare Services Ltd | Health & social care | 2019 |
| B H Cooper Ltd | Construction | 2021 |
| B H Grounds Maintenance Limited | Administrative & support | 2015 |
| B Ingram Rigging Ltd | Construction | 2015 |
| B Perry Scaffolding Limited | Construction | 2015 |
| B Team Joinery Ltd | Real estate | 2015 |