| Athena Teacher Training Ltd | Education | 2011 |
| Athena Technologies Ltd | Professional & scientific | 2024 |
| Athenai Ltd | Information & communication | 2023 |
| Athenas Enterprises Ltd | Wholesale & retail | 2025 |
| Atheris Technologies Limited | Wholesale & retail | 2025 |
| Athirt Limited | Financial services | 2021 |
| Athletes of the World Limited | Education | 2022 |
| Athmani & Co Limited | Information & communication | 2018 |
| Atkins Consultancy Limited | Real estate | 2019 |
| Atkinsons of Windermere Limited | Administrative & support | 1968 |
| Atlantis Developments (South) Ltd | Construction | 2014 |
| Atlas Inc Limited | Transport & logistics | 2011 |
| Atlas Partners (Hastings) 1 Ltd | Other services | 2016 |
| Atlas Partners (Hastings) Ltd | Real estate | 2015 |
| Atlas Voltage Ltd | Construction | 2025 |
| Atlassine Ltd | Wholesale & retail | 2024 |
| ATM Scaffoldingco. Ltd | Construction | 2003 |
| Atmb Studios Limited | Wholesale & retail | 2025 |
| Atmo Select Limited | Information & communication | 2015 |
| Atomic Vision Ltd | Wholesale & retail | 2016 |
| Atomic Welding Ltd | Manufacturing | 2024 |
| Atomix Analysis Ltd | Professional & scientific | 2026 |
| Atos Pro Build Ltd | Construction | 2026 |
| Atps Investments and Trading Limited | Financial services | 2023 |
| Atrex Media Ltd | Extraterritorial | 2021 |
| Atrnm Digital Ltd | Professional & scientific | 2021 |
| Atrook Limited | Wholesale & retail | 2025 |
| Atta Dost Ltd | Wholesale & retail | 2025 |
| Attayn Ltd | Professional & scientific | 2021 |
| Attic Group Ltd | Financial services | 2025 |
| Attic Online Ltd | Wholesale & retail | 2021 |
| Attic Property Ltd | Real estate | 2025 |
| Attic Textiles Limited | Wholesale & retail | 2010 |
| Attwoodman Ltd | Construction | 2024 |
| Atwhatcostclothing Ltd | Wholesale & retail | 2025 |
| Atwork Associates Limited | Real estate | 1998 |
| AU Design Services Ltd | Professional & scientific | 2017 |
| AUB Enterprises Limited | Real estate | 2003 |
| AUB Services Limited | Real estate | 1997 |
| Aubrey Commercial Services Ltd | Wholesale & retail | 2022 |
| Aubridge Venture Limited | Wholesale & retail | 2024 |
| Auction House Management Limited | Real estate | 2017 |
| Audeluxe Ltd | Wholesale & retail | 2025 |
| Audrayton Court Freehold Limited | Real estate | 2006 |
| AUF9 Ltd | Wholesale & retail | 2024 |
| Aufinity Ltd | Wholesale & retail | 2024 |
| Aura Lettings Limited | Real estate | 2017 |
| Auralogical Ltd | Information & communication | 2026 |
| Auraluxe Aesthetics Ltd | Other services | 2025 |
| Aurelion Commerce Ltd | Wholesale & retail | 2026 |
| Aureus Investment Management Ltd | Professional & scientific | 2021 |
| Aurevia Health Ltd | Health & social care | 2026 |
| Auriatek Ltd | Wholesale & retail | 2025 |
| Aurick PM Ltd | Other services | 2017 |
| Auris Piercing Ltd | Other services | 2025 |
| Aurora Business Solutions Ltd | Administrative & support | 2025 |
| Aurora Services Ltd | Professional & scientific | 2023 |
| Aurum Construction Services Limited | Professional & scientific | 2024 |
| Aurum Growth Ltd | Other services | 2026 |
| Auspicious BEE Ltd | Information & communication | 2012 |
| Austin Acquisitions 1 Ltd | Professional & scientific | 2020 |
| Austin Brickwork Holdings Limited | Financial services | 2025 |
| Austin Capital Limited | Professional & scientific | 2022 |
| Austin Motors Spares Service Limited | Wholesale & retail | 2018 |
| Austin Reproduction Parts Limited | Manufacturing | 2006 |
| Autavia Garage (Bournemouth) Limited | Real estate | 1975 |
| Authentic Education Group Limited | Education | 2012 |
| Authentic Thai Massage Limited | Other services | 2020 |
| Authentication Technologies Limited | Administrative & support | 2009 |
| Autismadhd Clinic Limited | Health & social care | 2022 |
| Auto Clubs International Limited | Information & communication | 2006 |
| Auto Sanctuary Ltd | Wholesale & retail | 2024 |
| Auto Service Garage (Bournemouth) Limited | Real estate | 1934 |
| Auto Tech SW Ltd | Wholesale & retail | 2019 |
| Auto Technology Publications Limited | Wholesale & retail | 2021 |
| Autoaid Group Ltd | Professional & scientific | 2025 |
| Automarine (UK) Limited | Manufacturing | 1998 |
| Automaton Consulting Limited | Information & communication | 2014 |
| Automotive Vision Ltd | Financial services | 2011 |
| Autorimessa Ltd | Transport & logistics | 2021 |
| Autospotuk Ltd | Wholesale & retail | 2018 |
| Autumn Repairs Limited | Construction | 2015 |
| Auxi Design Ltd | Professional & scientific | 2022 |
| AV Accounting Ltd | Professional & scientific | 2022 |
| AV ARG Ltd | Wholesale & retail | 2026 |
| AV Deals Ltd | Wholesale & retail | 2015 |
| AVA Fit Socials Ltd | Other services | 2024 |
| Avada Country Homes Ltd | Construction | 2018 |
| Avada Holdings Limited | Construction | 2012 |
| Avada Leisure Ltd | Arts & recreation | 2021 |
| Avada Ltd | Construction | 2001 |
| Avalanche Studio Limited | Wholesale & retail | 2025 |
| Avalon (Bournemouth) Ltd | Professional & scientific | 2012 |
| Avalon Defence Systems Limited | Manufacturing | 2025 |
| Avanelle Ltd | Wholesale & retail | 2025 |
| Avante (the Bays) Ltd | Construction | 2014 |
| Avante Lifestyle Ltd. | Administrative & support | 2011 |
| Avanti T&S Ltd | Transport & logistics | 2020 |
| Avardo Solutions Limited | Financial services | 2017 |
| AVC Group Limited | Financial services | 2015 |