| Alpha Eco Homes Ltd | Energy | 2024 |
| Alwa Design Studio Limited | Professional & scientific | 2016 |
| AM Plastering Ltd | Construction | 2024 |
| AMA Sunshine Property Ltd | Real estate | 2021 |
| Amazashop Ltd | Professional & scientific | 2025 |
| Amber Beardshall Ltd | Other services | 2026 |
| Amberdale Limited | Professional & scientific | 2015 |
| American Phoenix Ltd | Public administration | 2020 |
| Amethyst CPC Ltd | Health & social care | 2023 |
| AMG Management Services Ltd | Professional & scientific | 2025 |
| Amie Properties Limited | Real estate | 2024 |
| AMN Trade Ltd | Construction | 2025 |
| Amoreit Limited | Transport & logistics | 2017 |
| Amplusmed Ltd | Manufacturing | 2024 |
| AMS Law Services Ltd | Professional & scientific | 2015 |
| AMT Sports Media Limited | Administrative & support | 2020 |
| Analytical Property Solutions Limited | Real estate | 2017 |
| Andrew Godfrey Limited | Construction | 2013 |
| Andy Collins Plastering Ltd | Construction | 2021 |
| Andy's Cleaning Services Limited | Administrative & support | 2003 |
| Anest Iwata (UK) Limited | Wholesale & retail | 1993 |
| Angel Upholsterers Limited | Other services | 2015 |
| Anglian Gilt Producers Limited | Real estate | 2018 |
| Animore Stores Ltd | Wholesale & retail | 2026 |
| Annafield Homes Ltd. | Construction | 2013 |
| Annan Rail Ltd | Construction | 2018 |
| Annoyed Cat Ltd | Information & communication | 2018 |
| ANR Datamart Limited | Information & communication | 2015 |
| Anstee Gorst Ltd | Professional & scientific | 2015 |
| Anstee Partners Limited | Wholesale & retail | 2004 |
| Anti-Holiday Enterprise Ltd | Wholesale & retail | 2024 |
| Antonia Enterprise Ltd | Health & social care | 2019 |
| Anvil Design & Fabrication Limited | Manufacturing | 2017 |
| Anvio Ltd | Wholesale & retail | 2025 |
| Apatierra Ltd | Information & communication | 2025 |
| Apex Cost Management Limited | Administrative & support | 2008 |
| Apjh Trading Limited | Financial services | 2026 |
| APK Architecture & Design Ltd | Professional & scientific | 2020 |
| Apple NDT Limited | Professional & scientific | 2010 |
| Applegate Van Hire Ltd | Administrative & support | 2015 |
| Appliance Management Limited | Professional & scientific | 2005 |
| Applied Angle Consulting Limited | Professional & scientific | 2013 |
| Applied Insurtech Limited | Information & communication | 2023 |
| AQA Contracting Ltd | Other services | 2018 |
| AR Coombs Limited | Health & social care | 2017 |
| Arc-Iwe Limited | Manufacturing | 2014 |
| Arcadia Audio Solutions Ltd | Wholesale & retail | 2024 |
| Archer Heating and Plumbing Ltd | Construction | 2023 |
| Arctic Timber Limited | Wholesale & retail | 1993 |
| Arine Properties Limited | Households | 2021 |
| Arlia Broker Services Ltd | Financial services | 2021 |
| Armova Levin Ltd | Information & communication | 2023 |
| Arol Ltd | Professional & scientific | 2014 |
| Arqadian House Limited | Real estate | 2021 |
| Arrowsmith Financial Planning Limited | Other services | 2016 |
| Art of Health Ltd | Hospitality | 2019 |
| Artgerechte Torten Ltd | Administrative & support | 2024 |
| Artic Installs Ltd | Administrative & support | 2024 |
| Artisan Lens Collective Limited | Professional & scientific | 2026 |
| Arts Driving Academy Limited | Education | 2021 |
| Ascent Cafe Limited | Hospitality | 2025 |
| Asha Curry Ltd | Hospitality | 2026 |
| Asharry Limited | Real estate | 2014 |
| Ashbury Financial Ltd | Financial services | 2020 |
| Ashwell Asset Investments Ltd | Real estate | 2024 |
| ASJ Technical Services Limited | Wholesale & retail | 2015 |
| Aslan Management Ltd | Real estate | 2025 |
| Aslans Investments Group Limited | Real estate | 2023 |
| Aslans Investments Ltd | Real estate | 2022 |
| ASM Construct Ltd | Administrative & support | 2011 |
| Asmodella Ltd | Professional & scientific | 2024 |
| Assured Mortgage Advice Limited | Financial services | 2012 |
| AT Accounting & Company Services Limited | Professional & scientific | 2022 |
| AT Home Housing Ltd | Real estate | 2025 |
| Atai Global Ltd | Wholesale & retail | 2026 |
| Atao (UK) Limited | Professional & scientific | 2011 |
| Attis Advisers Ltd | Professional & scientific | 2025 |
| Audible Solutions Ltd | Other services | 2018 |
| Aufait Systems Limited | Information & communication | 2012 |
| Aunties Thai Ltd | Hospitality | 2016 |
| Aurora Game Studios Ltd | Information & communication | 2021 |
| Auspicious Tree Furniture Ltd | Other services | 2024 |
| Australian Formula Feeds Limited | Wholesale & retail | 2000 |
| Author's Edition Ltd | Other services | 2021 |
| Automation Software Technology Ltd | Information & communication | 2013 |
| Automotive Handling Solutions Ltd | Manufacturing | 2015 |
| Automotive Laser Cleaning Ltd | Wholesale & retail | 2025 |
| Avarum Investments Limited | Financial services | 2021 |
| Awor Ltd | Other services | 2018 |
| Axio-Maven Limited | Other services | 2007 |
| Axrat Ltd | Other services | 2018 |
| Aylin Permanent Make UP Ltd | Other services | 2022 |
| Ayman Ltd | Hospitality | 2020 |
| Ayuda Consulting Limited | Professional & scientific | 2009 |
| Azarias Training Ltd | Education | 2022 |
| Azure Water Treatment Services Ltd | Water & waste | 2010 |
| Azuruk Ltd | Wholesale & retail | 2023 |
| B Bright Cleaning Associates Limited | Administrative & support | 2015 |
| B G Building Solutions Ltd | Construction | 2013 |
| B Inspired Marketing Limited | Extraterritorial | 2016 |