| Aurelian Latu Ltd | Health & social care | 2022 |
| Aurevia Resources Limited | Mining & quarrying | 2025 |
| Auri Tech Ltd | Information & communication | 2025 |
| Aurola Facilities Limited | Administrative & support | 2007 |
| Auronis Group Limited | Health & social care | 2026 |
| Aurora Care Support Services Limited | Health & social care | 2025 |
| Aurora Harvest International Limited | Professional & scientific | 2016 |
| Aurorizon Properties Ltd | Real estate | 2024 |
| Aurum Home Solutions Ltd | Construction | 2025 |
| Austec Medical Services Ltd | Health & social care | 2023 |
| Auto Enrol ME Limited | Professional & scientific | 2014 |
| Auto Finesse Limited | Wholesale & retail | 2013 |
| Auto Heritage Ltd | Wholesale & retail | 2025 |
| Auto Maryo Cars Ltd | Manufacturing | 2018 |
| Auto Motor Excellence Ltd | Wholesale & retail | 2023 |
| Auto Motor Services Ltd | Wholesale & retail | 2025 |
| Auto Velvet Mobile Detailing Ltd | Wholesale & retail | 2021 |
| Autohaus Tech Ltd | Wholesale & retail | 2026 |
| Autolook Limited | Information & communication | 2015 |
| Automax Car Parts Limited | Wholesale & retail | 2019 |
| Autoprotect (MBI) Ltd | Financial services | 2004 |
| Autoprotect Administration Ltd | Administrative & support | 2004 |
| Autoprotect Group Limited | Financial services | 2017 |
| Autoquotes Limited | Information & communication | 2007 |
| Autotinder Ltd | Professional & scientific | 2022 |
| Avant Garde Hair & Beauty Ltd | Other services | 2017 |
| Aveka Financial Services Ltd | Professional & scientific | 2016 |
| Avelux Ltd | Information & communication | 2019 |
| Avenu Ltd | Real estate | 2026 |
| Avery Security Consulting Ltd | Administrative & support | 2026 |
| AVI Digital Limited | Information & communication | 2022 |
| AVM Interiors Ltd | Construction | 2026 |
| Avnil Nexus Ltd | Wholesale & retail | 2025 |
| Avon Court (Ponders END) Management Company Limited | Households | 1986 |
| Avondale Medical Services Ltd | Health & social care | 2023 |
| Avra Construction Ltd | Construction | 2018 |
| AVZ Statistics Ltd | Administrative & support | 2017 |
| Awaken Legacy Estate Limited | Real estate | 2025 |
| Awakened Heart Ltd | Other services | 2025 |
| AWD Ltd | Wholesale & retail | 2025 |
| Awesome Associates Ltd | Information & communication | 2017 |
| Awesome Health and Wellness Limited | Health & social care | 2025 |
| AWL Products Ltd | Wholesale & retail | 2026 |
| Awoviancares Limited | Health & social care | 2024 |
| AX Ameen Consult & Supply Ltd | Administrative & support | 2015 |
| Axiom Recruitment Ltd | Administrative & support | 2021 |
| Axis Business & Management Consultancy Ltd | Professional & scientific | 2021 |
| Axon Algorithms Limited | Information & communication | 2014 |
| Axora Solutions Ltd | Wholesale & retail | 2025 |
| Axoro Ltd | Wholesale & retail | 2024 |
| AY Autos Limited | Manufacturing | 2016 |
| AY Garden Design Ltd | Other services | 2021 |
| Aybams Limited | Health & social care | 2021 |
| Ayel Properties SPV Limited | Real estate | 2025 |
| Ayibu Ltd | Health & social care | 2022 |
| Ayissi Business Consulting Ltd | Professional & scientific | 2024 |
| Aylesbury House RTM Company Limited | Households | 2010 |
| Aylida Ltd | Wholesale & retail | 2024 |
| AYM AI Limited | Information & communication | 2025 |
| Aymel Supply Ltd | Wholesale & retail | 2026 |
| Aynaglass Ltd | Administrative & support | 2014 |
| AYO Sowunmi & Associates Ltd | Professional & scientific | 2007 |
| Ayomide Abiola Ltd | Health & social care | 2024 |
| Ayotech Ltd | Information & communication | 2019 |
| Aysha Private Ltd | Hospitality | 2024 |
| Aytac Limited | Hospitality | 2025 |
| AZ Sourcing Ltd | Real estate | 2021 |
| AZ Younis Holding Ltd | Financial services | 2022 |
| AZ Younis Properties Ltd | Real estate | 2021 |
| Azar Properties Ltd | Real estate | 2023 |
| Azat Properties Ltd | Real estate | 2025 |
| Azibi Asset Management Limited | Real estate | 2013 |
| Aziz Ways Ltd | Transport & logistics | 2025 |
| AZO Health Limited | Health & social care | 2026 |
| Azom Enterprise Limited | Hospitality | 2018 |
| Azriel Limited | Real estate | 2021 |
| Azurvista Limited | Health & social care | 2006 |
| B & H Ambassador's Harlow Ltd | Other services | 2018 |
| B a Business Management Limited | Other services | 2017 |
| B Akhtars Limited | Hospitality | 2019 |
| B J Carters Limited | Construction | 2022 |
| B Steelfixing Ltd | Construction | 2021 |
| B&B Interiors Limited | Construction | 2025 |
| B&D Scaffolding and Rigging Services Ltd | Construction | 2016 |
| B&M Construction and Property Services Limited | Construction | 2020 |
| B&M Contract Cleaning Services Ltd | Administrative & support | 2022 |
| B&N Building and Renovation Ltd | Construction | 2022 |
| B&S Kolade Ltd | Health & social care | 2023 |
| B&T Home Improvements Ltd | Construction | 2021 |
| B&T Property Services Ltd | Construction | 2023 |
| B-Bak Healthcare Ltd | Health & social care | 2022 |
| B-Pack Print Ltd | Manufacturing | 2024 |
| B. Stapleton & SON Limited | Wholesale & retail | 2008 |
| B.A.R Engineering Ltd | Manufacturing | 2014 |
| B.B.& C.Fencing Limited | Construction | 1960 |
| B.G. Shkolo UK Limited | Education | 2017 |
| B.H.P. Management Company Limited | Households | 1981 |
| B.P.S. Security Installation Limited | Manufacturing | 2006 |
| B12VITALIZED Ltd | Health & social care | 2020 |
| B2 Cleaning Services Ltd | Administrative & support | 2023 |