| Aurion Capital Partners Limited | Professional & scientific | 2026 |
| Aurum (Nottingham) Ltd | Real estate | 2022 |
| Aurum Corporate Introductions Ltd | Administrative & support | 2025 |
| Aurumknight Compliance & Technology Limited | Information & communication | 2025 |
| Ausbert Valley Community Interest Company | Administrative & support | 2021 |
| Austin Automation Limited | Information & communication | 2019 |
| Austin Build Co Limited | Construction | 2024 |
| Austin Gray LLP | | 2007 |
| Authentic Brew Limited | Manufacturing | 2024 |
| Authentic Business Coaching Ltd | Professional & scientific | 2023 |
| Authentic Memorabilia and Autographs Ltd | Wholesale & retail | 2023 |
| Autism & Aspergers Care Services Ltd | Health & social care | 2010 |
| Autism & Aspergers Support Ltd | Health & social care | 2010 |
| Auto Marine Technics Limited | Administrative & support | 2006 |
| Autochain Limited | Information & communication | 2024 |
| Autoevents Ltd | Arts & recreation | 2009 |
| Autohaus Automotive Limited | Wholesale & retail | 2021 |
| Autohub Autocentres (Brighton) Ltd | Wholesale & retail | 2025 |
| Autohub Autocentres (Eastbourne) Ltd | Wholesale & retail | 2025 |
| Autohub Autocentres (Technical) Ltd | Wholesale & retail | 2025 |
| Automated Dynamics Limited | Professional & scientific | 2024 |
| Automated Systems Integration Limited | Construction | 2012 |
| Automation One Ltd | Manufacturing | 2022 |
| Automation Technologies Ltd | Manufacturing | 1989 |
| Automind Vehicle Diagnostics Limited | Information & communication | 2025 |
| Automotive Ledger Ltd | Information & communication | 2025 |
| Autospeedwatch Limited | Manufacturing | 2018 |
| Autumn Wolf Holdings Ltd | Administrative & support | 2016 |
| Auxilium Community Housing CIC | Real estate | 2024 |
| Auzanne Ltd | Construction | 2022 |
| AVA Athanasius Ltd | Wholesale & retail | 2023 |
| AVA Engineering Services Ltd | Professional & scientific | 2018 |
| AVA Property Services Ltd | Real estate | 2020 |
| Avalara EU Holdings UK Limited | Information & communication | 2015 |
| Avalara Europe Ltd | Information & communication | 2013 |
| Avalon Dance Odyssey CIC | Health & social care | 2025 |
| Avalon Financial (Homes) Limited | Construction | 2002 |
| Avalon Financing Ventures Limited | Construction | 1999 |
| Avalon Futures Limited | Extraterritorial | 2013 |
| Avalon Management (Brighton) Limited | Households | 2003 |
| Avalon Projects LLP | | 2013 |
| Avalon Seaford Limited | Construction | 2015 |
| Avant Garde Accountancy Ltd | Professional & scientific | 2018 |
| Avant Garde Estates Ltd | Real estate | 2020 |
| Avante Ltd | Administrative & support | 2004 |
| Avard Property Management Ltd | Real estate | 2020 |
| AVB13 Ltd | Real estate | 2021 |
| Aven Medical UK Ltd | Manufacturing | 2020 |
| Avenal Ausden Limited | Administrative & support | 2019 |
| Avenue Court (Hove) Freeholders Limited | Households | 1999 |
| Avenue Investment Properties Ltd | Construction | 2014 |
| Avenue Lodge LLP | | 2022 |
| AVENUE2 Limited | Manufacturing | 2013 |
| Avercamp Limited | Professional & scientific | 2014 |
| Aviaer Holdings Limited | Wholesale & retail | 2014 |
| Aviator Travel Limited | Administrative & support | 2010 |
| Aviatrix Limited | Professional & scientific | 2012 |
| Avicenna Centre for Chinese Medicine Limited | Health & social care | 2009 |
| Avicenna Herbs Limited | Hospitality | 2014 |
| Avicenna Property Ltd | Real estate | 2022 |
| Avighna Solutions Limited | Information & communication | 2008 |
| Avis Business Consulting Limited | Professional & scientific | 2016 |
| Avix Pharmaceuticals Limited | Manufacturing | 2018 |
| Avnesha Event Management Ltd | Administrative & support | 2020 |
| Avocet Design Consultancy Ltd | Professional & scientific | 2024 |
| Avollia Ltd | Wholesale & retail | 2025 |
| AVR Solution Ltd | Construction | 2018 |
| Avril Limited | Administrative & support | 1999 |
| Avro Energy Limited | Wholesale & retail | 2014 |
| AVT Group Limited | Professional & scientific | 1997 |
| AVT Ltd. | Information & communication | 1975 |
| AW Homes and Investments Ltd | Real estate | 2023 |
| Awards Intelligence Limited | Professional & scientific | 2007 |
| AWC Contractors Limited | Administrative & support | 2007 |
| Awcfa Limited | Information & communication | 2004 |
| Awen Furniture Limited | Wholesale & retail | 2022 |
| Awful Good Limited | Professional & scientific | 2019 |
| Aws-Rigging Ltd | Information & communication | 2020 |
| AWT Digital Ltd | Information & communication | 2022 |
| AWT Finance Limited | Financial services | 2025 |
| AWT Investments Limited | Real estate | 2013 |
| Axiom Hvac Limited | Professional & scientific | 2020 |
| Axis Estate Planning Limited | Professional & scientific | 2025 |
| Axis Wealth Management Limited | Financial services | 2011 |
| AXIS3 Consulting Ltd | Administrative & support | 2019 |
| Axle Events Ltd | Arts & recreation | 2023 |
| AY Barbeque Limited | Hospitality | 2025 |
| Ayan Patel Limited | Wholesale & retail | 2023 |
| Ayerspartners Ltd | Wholesale & retail | 2024 |
| Ayla and Friends Ltd | Wholesale & retail | 2025 |
| Aylesview Limited | Real estate | 1980 |
| Aylin Brighton Ltd | Other services | 2021 |
| AYM Enterprises Ltd | Wholesale & retail | 2019 |
| Ayurveda Training and Products UK Ltd | Health & social care | 2018 |
| Ayzel Limited | Other services | 2021 |
| Azalea Systems Limited | Information & communication | 1993 |
| Azarfield Properties Limited | Real estate | 2026 |
| Aziza Indian Ltd | Hospitality | 2019 |
| Azlans Universe Ltd | Wholesale & retail | 2023 |
| Azul Marketing Ltd | Other services | 2023 |