| Alfa Leadership & Wellbeing Ltd | Professional & scientific | 2023 |
| Alfred & Eleanor Limited | Real estate | 2016 |
| Alif ZAN Ltd | Extraterritorial | 2022 |
| Alistair Grant Freelance Ltd | Information & communication | 2012 |
| ALL Eco Solutions Limited | Water & waste | 2022 |
| ALL Nations Christian College Limited | Hospitality | 1970 |
| Alma Cafe Ware Ltd | Hospitality | 2018 |
| Alpha Aero Services Ltd | Transport & logistics | 2017 |
| Altura Group Holdings Ltd | Financial services | 2025 |
| Always Smiling Limited | Information & communication | 2005 |
| Amatsa Limited | Wholesale & retail | 2025 |
| AMB Engineering and Technology Limited | Professional & scientific | 2023 |
| AMC QS Limited | Professional & scientific | 2015 |
| Americanpost Ltd | Information & communication | 2022 |
| Amethyst Financial Limited | Professional & scientific | 2005 |
| AMG Home Solutions Ltd | Construction | 2025 |
| Amicus IT Consulting Ltd | Information & communication | 2018 |
| Aminoe Ltd | Other services | 2025 |
| AMP Management Services Ltd | Construction | 2019 |
| Amwell Blast Coat Ltd | Manufacturing | 2010 |
| Amwell BTL Investments Limited | Real estate | 2019 |
| Amwell END Taproom Ltd | Hospitality | 2022 |
| Amwell Fruit Company Limited | Wholesale & retail | 2010 |
| Amwell Investments Limited | Real estate | 2004 |
| Amwell Prestige Limited | Construction | 2014 |
| Anantaya Group Ltd | Information & communication | 2025 |
| Anderson Flooring Contractors Ltd | Construction | 2026 |
| Andrew Boakes Developments Limited | Construction | 2006 |
| Andrew Jackson Design Ltd | Professional & scientific | 2019 |
| Andrew Jackson Waste Ltd | Water & waste | 2022 |
| Andrews Fish Bar Ltd | Hospitality | 2021 |
| Andrews Tutorials Limited | Education | 2021 |
| Anglo Chinese Aerospace Limited | Professional & scientific | 2008 |
| Anita Louise Consultancy Ltd | Professional & scientific | 2025 |
| Anla Consulting Ltd | Professional & scientific | 2026 |
| Anna Stephenson Ltd | Arts & recreation | 2019 |
| Annabel Dimmock Limited | Arts & recreation | 2017 |
| Annamei Property Limited | Real estate | 2024 |
| Another Level Community Fitness C.I.C. | Arts & recreation | 2024 |
| ANT Strategy Ltd | Real estate | 2022 |
| Anthony Howes Limited | Construction | 2015 |
| Anthony Lloyd Furniture Limited | Manufacturing | 2022 |
| Antiks Events Limited | Administrative & support | 2024 |
| AP Construction & Renovation Ltd | Other services | 2023 |
| AP Home Maintenance Ltd | Other services | 2023 |
| APA Live Events Ltd | Arts & recreation | 2010 |
| Apex Air Ltd | Transport & logistics | 1998 |
| APG Wealth Management Ltd | Professional & scientific | 2015 |
| Appearance Developments Ltd | Construction | 2023 |
| Applied Engineering Limited | Construction | 2009 |
| Apton Court (Management) Company Limited | Households | 1971 |
| Aqua Aromas Ltd | Wholesale & retail | 2023 |
| Arabis Accountancy Services Ltd | Professional & scientific | 2018 |
| Archie's Pet Supplies Ltd | Manufacturing | 2026 |
| Architectural Metal Solutions Ltd | Manufacturing | 2011 |
| Architectural Surplus Supplies Ltd | Real estate | 2015 |
| Archrealm Action Design Limited | Arts & recreation | 2025 |
| Arim Limited | Administrative & support | 2019 |
| Ariztech Ltd | Other services | 2026 |
| Armoury Limited | Extraterritorial | 2008 |
| Artemis Security Ltd | Financial services | 2025 |
| Artworkservices Limited | Information & communication | 2003 |
| ARW Holdings Ltd | Hospitality | 2017 |
| Asap Cars Ltd | Transport & logistics | 2018 |
| Asap Taxis Ltd | Transport & logistics | 2024 |
| Asap Used Cars Ltd | Wholesale & retail | 2024 |
| Ascension Digital Limited | Information & communication | 2019 |
| Asgard Technologies Limited | Information & communication | 2008 |
| Ashbourne and Ashbourne Limited | Hospitality | 2022 |
| Ashbourne PUB Group Limited | Hospitality | 2024 |
| Ashford Grey Limited | Wholesale & retail | 2025 |
| Aspect Window Films Ltd | Construction | 2016 |
| Asprey Hyde Developments Ltd | Construction | 2017 |
| Asquith and Company (Refrigeration) Limited | Extraterritorial | 2012 |
| Association of Energy Engineers (UK) Limited | Other services | 2022 |
| Astoria Care Consultancy Ltd | Professional & scientific | 2022 |
| Atalanta Investments Limited | Professional & scientific | 1893 |
| Atelier Red Limited | Professional & scientific | 2014 |
| Athlon Fitness Herts Limited | Arts & recreation | 2018 |
| Atlas Sales Consulting Ltd | Professional & scientific | 2023 |
| Audley Investments Limited | Professional & scientific | 1977 |
| August Blue Limited | Real estate | 2017 |
| Aurum & Argent Ltd | Wholesale & retail | 2019 |
| Auspicium Limited | Administrative & support | 2006 |
| Auto Facilitas Ltd | Administrative & support | 2025 |
| AUTOM8ERS Ltd | Information & communication | 2023 |
| Auxilium GC Limited | Professional & scientific | 2019 |
| AV Trading Ltd | Construction | 2024 |
| Avenue 38 Ltd | Administrative & support | 2023 |
| Avery Construction Limited | Construction | 2015 |
| Aves Ware LLP | | 2024 |
| AVL Accounting Services Limited | Professional & scientific | 2002 |
| Aware Leadership Ltd | Education | 2014 |
| Awesome Publishing Limited | Information & communication | 2016 |
| Awridian Consulting Ltd | Professional & scientific | 2024 |
| Axiom UX Ltd | Information & communication | 2025 |
| Axiomiq Ltd | Professional & scientific | 2025 |
| Aylesburyescaperooms Ltd | Arts & recreation | 2018 |
| B and I Partners Limited | Professional & scientific | 2017 |
| B Mccarthy Construction Limited | Construction | 2019 |