| APS Courier Ltd | Transport & logistics | 2023 |
| APS Test Solutions Ltd | Information & communication | 2013 |
| Apsley Court Freeholders Company (Sussex) Limited | Households | 1978 |
| APT Partnership Limited Liability Partnership | | 2008 |
| Aquila Supplies Limited | Wholesale & retail | 2023 |
| Aquirecom Limited | Public administration | 2014 |
| AR Builders Bidborough Ltd | Construction | 2021 |
| AR Detailing Limited | Administrative & support | 2026 |
| Ar&Team Property Limited | Real estate | 2025 |
| Arabena Associates Ltd | Information & communication | 2025 |
| Aragon Consulting Ltd | Administrative & support | 2018 |
| Arbus Black Investments Limited | Real estate | 2013 |
| ARC 2005 Holdings Limited | Financial services | 2025 |
| ARC Properties Limited | Real estate | 2022 |
| Arcadent Ltd | Health & social care | 2025 |
| Archimedes Pythagoras Real Estate Ltd | Real estate | 2023 |
| Architechs Hosting Software LLP | | 2016 |
| Architechs Solutions Ltd | Information & communication | 2003 |
| Architectural Office Michael Dillon Limited | Professional & scientific | 2022 |
| Architecturally Ltd | Information & communication | 2023 |
| Archmagepress Ltd | Information & communication | 2025 |
| Archway Automotive Ltd | Administrative & support | 2012 |
| Arcminal Limited | Information & communication | 2019 |
| Ardstone Select European Markets LP | | 2011 |
| Ardvantage Limited | Information & communication | 2019 |
| Aresbe Capital Limited | Real estate | 2025 |
| Aria London Consulting Ltd | Professional & scientific | 2024 |
| Aries Dispute Resolution Limited | Professional & scientific | 2018 |
| Aries GNH (GP 2) Limited | Professional & scientific | 2009 |
| Arigeo Limited | Administrative & support | 2023 |
| Ariica Limited | Wholesale & retail | 2024 |
| Arika Management Services Limited | Real estate | 2020 |
| Arixian Ltd | Professional & scientific | 2021 |
| ARJ Foods Ltd | Hospitality | 2024 |
| ARK Design Build Limited | Construction | 2017 |
| Arken.Legal (UK) Limited | Information & communication | 1992 |
| Arkitecht Limited | Information & communication | 2016 |
| Arkiton Roofing & Building Ltd | Administrative & support | 2017 |
| Arkitype Limited | Professional & scientific | 2022 |
| Arko Property LLP | | 2012 |
| Arleo Property Group Ltd | Hospitality | 2025 |
| ARM Global Ltd | Wholesale & retail | 2022 |
| Armadillo Electrics and Renewables Ltd | Construction | 2025 |
| Armadillo Shield Limited | Administrative & support | 2009 |
| Armadillo Sun Limited | Wholesale & retail | 2020 |
| Armour Taylor Ltd | Hospitality | 2024 |
| Armour Trading Ltd | Wholesale & retail | 2024 |
| Armstrong Enterprises Limited | Public administration | 2015 |
| Arpenteur Eltham Holdings Limited | Financial services | 2022 |
| Arpenteur Eltham Limited | Construction | 2022 |
| Arpenteur Limited | Construction | 2019 |
| Arqeye Ltd | Information & communication | 2025 |
| Arran Critchley Ltd | Professional & scientific | 2025 |
| Artcinema Global Ltd | Professional & scientific | 2024 |
| Artdobro Ltd | Arts & recreation | 2023 |
| Artechra Limited | Information & communication | 2025 |
| Artemide Ltd | Health & social care | 2019 |
| Artesian Consulting Limited | Professional & scientific | 1999 |
| Arthur Health Ltd | Financial services | 2024 |
| Arthur Healthcare Ltd | Financial services | 2026 |
| Artifactual Software Ltd | Information & communication | 2024 |
| Artiga Limited | Professional & scientific | 2025 |
| Artisan Storage Ltd | Transport & logistics | 2020 |
| Artnode Limited | Professional & scientific | 2025 |
| Artnode Services Limited | Professional & scientific | 2025 |
| Artt & Sons Limited | Construction | 2024 |
| Artup Ltd | Manufacturing | 2020 |
| Artwork Platform Systems Ltd | Information & communication | 2021 |
| Artz Ltd | Real estate | 2016 |
| Aruka Systems Ltd | Information & communication | 2013 |
| Arundel House Management Company Limited | Households | 1991 |
| Aryon Limited | Information & communication | 2026 |
| ASA Prime Ltd | Hospitality | 2026 |
| Asap Cloud Solutions Limited | Information & communication | 2018 |
| Ascender Consulting Ltd | Administrative & support | 2020 |
| Ascender Holdings Limited | Other services | 2020 |
| ASD GAS Ltd | Construction | 2025 |
| Aseti Ltd | Information & communication | 2026 |
| ASH Building Contractors Limited | Construction | 2008 |
| ASH Estate Management Ltd | Households | 2025 |
| ASH Invest LLP | | 2013 |
| Ashana Intelligence Ltd | Professional & scientific | 2024 |
| Ashbrook Execu Ltd | Transport & logistics | 2020 |
| Ashburnhams Limited | Real estate | 2009 |
| Ashdown Court (Forest ROW) Management Limited | Real estate | 2009 |
| Ashdown Court Freeholders Limited | Real estate | 2019 |
| Ashdown Forest Economic Development LLP | | 2013 |
| Ashdown Wells Limited | Administrative & support | 2019 |
| Asher Wellspring Ltd | Health & social care | 2025 |
| Ashington for Investment Limited | Real estate | 2015 |
| Ashley Green Research Limited | Construction | 2014 |
| Ashley House Management (Tunbridge Wells) Limited | Households | 1983 |
| Ashshot Limited | Real estate | 1989 |
| Ashton Price Design Limited | Professional & scientific | 2020 |
| Ashton Talent Solutions Limited | Administrative & support | 2025 |
| Ashurst Executives Limited | Professional & scientific | 2010 |
| Ashwood Court Limited | Households | 2003 |
| Asim & Raza Holdings Limited | Administrative & support | 2022 |
| Asjcon Limited | Transport & logistics | 2023 |
| Askin Properties Ltd | Real estate | 2024 |