| Alltrades Building & Maintenance (Essex) Ltd | Construction | 2009 |
| ALP Finance Limited | Administrative & support | 2025 |
| Alphamerce Limited | Wholesale & retail | 2016 |
| Alpine Insurance Services (Holdings) Limited | Financial services | 2001 |
| Alpine Insurance Services Limited | Financial services | 1986 |
| Alpine Windows and Doors Ltd | Construction | 2023 |
| Altitude Aviation Services Ltd | Professional & scientific | 2024 |
| Altradez Property Services Ltd | Professional & scientific | 2021 |
| Alur Payments Consultants Ltd | Professional & scientific | 2020 |
| Always Security Ltd | Administrative & support | 2020 |
| AM Services (South East) Ltd | Extraterritorial | 2011 |
| Amanda Holden Financial Planning Ltd | Financial services | 2023 |
| Amani Property Investments Limited | Real estate | 2020 |
| Amazonas Tarphat Limited | Wholesale & retail | 2021 |
| Ambiotek Community Interest Company | Manufacturing | 2011 |
| Amchara Juicery Ltd | Wholesale & retail | 2011 |
| Amchara Limited | Health & social care | 2022 |
| Amco Windows and Doors Ltd | Construction | 2016 |
| AMD Logistical Ltd | Transport & logistics | 2019 |
| Ames Temperature Solutions Limited | Construction | 2021 |
| Amplify My Probe Ltd | Professional & scientific | 2020 |
| Ampstream Limited | Real estate | 2017 |
| Ampt Service and Trading Limited | Wholesale & retail | 2017 |
| Amptec Electrical Services Ltd | Construction | 2022 |
| Anaesthetic Consultants Essex LLP | | 2024 |
| Analysis Solutions Services Limited | Information & communication | 2018 |
| Anderson Recovery Services Limited | Professional & scientific | 2016 |
| Andre Engelbrecht Limited | Professional & scientific | 2018 |
| Andrew Cooper Plumbing & Heating Ltd | Construction | 2022 |
| Andrew Estates Ltd | Real estate | 2018 |
| Andrew James Ltd | Extraterritorial | 2021 |
| Andrews Taxis Ltd | Transport & logistics | 2016 |
| Angela Foulds Ltd | Administrative & support | 2023 |
| Angelmage Consultancy Services Ltd | Information & communication | 2022 |
| Anglian Care Limited | Education | 2007 |
| Anglian Care Services Limited | Education | 2007 |
| Anmor Carpentry Ltd | Construction | 2016 |
| ANN Galvin Business Consultancy Limited | Professional & scientific | 2011 |
| Annwn Associates Limited | Education | 2026 |
| Anopa Limited | Health & social care | 2013 |
| Another View Financial Services Ltd | Administrative & support | 2021 |
| Another View Wills Ltd | Professional & scientific | 2026 |
| ANP Estate Ltd | Real estate | 2021 |
| ANP Solicitors Limited | Professional & scientific | 2009 |
| Antero Consulting Ltd | Administrative & support | 2016 |
| Anthea Vandermolen Interiors Limited | Wholesale & retail | 2005 |
| Anthony Jackson Properties Ltd | Real estate | 2019 |
| Anthony Johnston Installations Ltd | Construction | 2013 |
| Antodave Ltd | Health & social care | 2020 |
| AOS Group Ltd | Professional & scientific | 2026 |
| Apaa Management Services Ltd | Wholesale & retail | 2026 |
| Apex 24/7 Ltd | Health & social care | 2024 |
| Apex Fire Consultancy Ltd | Professional & scientific | 2026 |
| Apfs Holdings Ltd | Financial services | 2023 |
| APH Electrical Services Ltd | Construction | 2021 |
| Aplan Build Ltd | Construction | 2025 |
| Aplan Commercial Ltd | Construction | 2025 |
| Aplan Industrial Ltd | Construction | 2025 |
| Apollo Finance and Risk Consulting Ltd | Professional & scientific | 2022 |
| Apozem Ltd | Wholesale & retail | 2025 |
| Appans Superstore Ltd | Wholesale & retail | 2016 |
| Apply Within Ltd | Professional & scientific | 2024 |
| Approved Fireplace Installers Limited | Administrative & support | 2004 |
| Apsco Ltd | Wholesale & retail | 2025 |
| APU Kuntur Consulting Ltd | Information & communication | 2017 |
| Aqualog Limited | Administrative & support | 2000 |
| Aquarius Contractors Ltd | Construction | 2025 |
| Aquaseal Liquid Roofing Innovations Ltd | Construction | 2025 |
| AR Systems and Software Limited | Professional & scientific | 2025 |
| Arakot Limited | Hospitality | 2022 |
| Aram's Property Limited | Real estate | 2024 |
| Arcc Group Limited | Construction | 2018 |
| Arch 10 Ltd. | Professional & scientific | 2022 |
| Arch Placed People Ltd | Transport & logistics | 2024 |
| Archer Building Consultancy Limited | Professional & scientific | 2007 |
| Archi-Tri Ltd | Professional & scientific | 2013 |
| Archikloos Limited | Professional & scientific | 2022 |
| Argent Asset Management Limited | Professional & scientific | 2017 |
| Argent Commercial Developments Limited | Construction | 2021 |
| ARK Plumbing & Heating Solutions Ltd | Construction | 2019 |
| Arkival Ltd | Professional & scientific | 2024 |
| Arkstone Media Ltd | Professional & scientific | 2025 |
| Arlo Rome Limited | Wholesale & retail | 2023 |
| Armiger Training Services Ltd | Education | 2016 |
| Armob Ltd | Wholesale & retail | 2024 |
| ARN Scaffolding Ltd | Construction | 2024 |
| Aroo Limited | Real estate | 2021 |
| Around Advertising Ltd | Information & communication | 2026 |
| Arrval Properties Limited | Real estate | 2024 |
| Arslan Financial Limited | Construction | 2022 |
| Art Blinds Limited | Wholesale & retail | 2002 |
| Art Sign & Graphics Limited | Manufacturing | 2002 |
| Arte Heating & Renewables Ltd | Construction | 2021 |
| Artemis Bookbinders Limited | Administrative & support | 2010 |
| Artful Dodger Services Limited | Wholesale & retail | 2019 |
| Aruok Ltd | Wholesale & retail | 2025 |
| AS Knight Electrical Limited | Construction | 2023 |
| Asbestos Conformance Limited | Professional & scientific | 2024 |
| Asbestos Consultancy International Ltd | Professional & scientific | 2018 |
| Ascot Building Services Ltd | Administrative & support | 1999 |