| Apex Development Advisory Ltd | Professional & scientific | 2025 |
| Apex Endodontics Ltd | Health & social care | 2018 |
| Apex GAS Solutions Ltd | Construction | 2026 |
| Apex Marquee and Gazebo Hire Limited | Hospitality | 2023 |
| Apex Medical Consulting Ltd | Health & social care | 2014 |
| Apexendo Ltd | Health & social care | 2018 |
| Aphobos Crossfit Fitness Group Ltd | Arts & recreation | 2024 |
| APM - Electrical Limited | Construction | 2025 |
| Apnhome Limited | Professional & scientific | 2026 |
| Apollo Learning Ltd | Education | 2019 |
| Appear Natural Aesthetics Limited | Other services | 2019 |
| Apple Distributors International Ltd | Hospitality | 2020 |
| Apple Jacks Children Service Limited | Health & social care | 2025 |
| Apple Tree Court (Lewisham) RTM Company Limited | Real estate | 2021 |
| Apple Tree Living Limited | Real estate | 2018 |
| Appleburry Ltd | Health & social care | 2024 |
| Appleton IP Limited | Administrative & support | 2008 |
| Application Test Limited | Information & communication | 2012 |
| Applied Risk Technology Ltd | Professional & scientific | 2012 |
| Apply Online Limited | Information & communication | 2019 |
| Appollo Homes Limited | Administrative & support | 2005 |
| Apponotec Limited | Information & communication | 2008 |
| Appraise Housing Services Ltd | Hospitality | 2020 |
| Approved Limited | Information & communication | 2015 |
| Apps I.T. Limited | Administrative & support | 2001 |
| Après School Limited | Health & social care | 2023 |
| APS 888 Ltd | Financial services | 2021 |
| APS A/C Limited | Construction | 2023 |
| APX Estate Agents SE Ltd | Real estate | 2022 |
| Aqua Brasserie Bromley Limited | Hospitality | 2012 |
| Aqua Drip Plumbing and Heating Ltd | Construction | 2024 |
| Aqua Pizza Limited | Hospitality | 2022 |
| Aquaross Plumbing, Heating, General Domestic Maintenance Ltd | Construction | 2017 |
| Aquila Construction Solutions Ltd | Construction | 2025 |
| Aquinas Church of England Education Trust Limited | Education | 2011 |
| Aquisolve Services Ltd | Professional & scientific | 2013 |
| AR Roofing Ltd | Construction | 2026 |
| Araind Limited | Information & communication | 2022 |
| Aram Advisory Ltd | Professional & scientific | 2026 |
| Aramis Solutions Limited | Financial services | 2025 |
| Aranya Ltd | Information & communication | 2024 |
| Arayaz Ltd | Hospitality | 2015 |
| ARB London Ltd | Water & waste | 2018 |
| Archaeology Agents Ltd | Wholesale & retail | 2015 |
| Archgrade Designs Ltd | Professional & scientific | 2019 |
| Archimedes SP Holdings Limited | Financial services | 2021 |
| Archipelago Trading Limited | Health & social care | 2002 |
| Architectural Partner Network Limited | Professional & scientific | 2026 |
| Arctec Construction Ltd | Construction | 2015 |
| Arcus Prosperus Limited | Hospitality | 2025 |
| Ardenhurst Property Management Limited | Real estate | 2006 |
| Ardent Living Ltd | Health & social care | 2025 |
| Arena Kitchens Ltd | Wholesale & retail | 2017 |
| Ares Yachting Ltd | Extraterritorial | 2024 |
| Arete Leisure Ltd | Professional & scientific | 2013 |
| ARG Connects Limited | Wholesale & retail | 2020 |
| ARG Construction Projects Ltd | Construction | 2021 |
| Argnoric Ltd | Information & communication | 2021 |
| Argo Property Trading Ltd | Real estate | 2004 |
| Argoswift Limited | Real estate | 1978 |
| Argus Analytics and Transformation Ltd | Professional & scientific | 2017 |
| Arhal Limited | Hospitality | 2025 |
| ARI Connects Limited | Information & communication | 2010 |
| Aria Private Ltd | Real estate | 2014 |
| Ariana Properties Ltd | Real estate | 2017 |
| Aries Legal Practice Management Ltd | Administrative & support | 2023 |
| Ario Worldwide Limited | Manufacturing | 2026 |
| Arixcel Limited | Information & communication | 2009 |
| Arjun & Aishwarya IT Solutions Ltd | Information & communication | 2021 |
| Arjun & Aishwarya Properties Ltd | Real estate | 2020 |
| Arkle Court RTM Company Limited | Households | 2023 |
| Arlington Capital Markets Limited | Professional & scientific | 2018 |
| Armada Computer Accounting Limited | Professional & scientific | 1982 |
| Armando Pinzon Ltd | Information & communication | 2015 |
| Armou Investments Limited | Real estate | 2004 |
| Armou Property Investments LLP | | 2017 |
| Armoury Homes Ltd | Real estate | 2021 |
| Armstrong & Sons Roofing & Building Ltd | Construction | 2023 |
| Armz and CEY Ventures Limited | Real estate | 2025 |
| Arnold Foster Construction Limited | Construction | 2020 |
| Arnold Solutions Limited | Professional & scientific | 2022 |
| Arnoutt & James Limited | Construction | 2022 |
| Aroma Property Services Ltd | Hospitality | 2015 |
| Aroma Property Stays Ltd | Hospitality | 2025 |
| ARP Bespoke Travel Ltd | Administrative & support | 2026 |
| ARP Investhub Limited | Information & communication | 2024 |
| Arpol Limited | Construction | 2007 |
| Arreus Ltd | Construction | 2020 |
| Artbuilding Ltd | Construction | 2017 |
| Artemis IM 2 Limited | Real estate | 2016 |
| Artemis IM Holdings Ltd | Financial services | 2026 |
| Artemis IM Ltd | Real estate | 2014 |
| Arthur Court (Private Block) Management Company Limited | Households | 2016 |
| Arthur Meek Limited | Arts & recreation | 2016 |
| Artificial Intelligence Radio Ltd | Information & communication | 2021 |
| Artiforge Ltd | Information & communication | 2025 |
| Artisan Homes Limited | Professional & scientific | 2002 |
| Artsabelle Ltd | Arts & recreation | 2020 |
| Artsolio Ltd | Wholesale & retail | 2023 |
| Arttain Law Ltd | Professional & scientific | 2018 |