| Andrew Hunt Holdings Limited | Households | 2023 |
| Andrews & O`Shea Ltd | Professional & scientific | 2008 |
| Anelie Ltd | Health & social care | 2018 |
| Angel Cerda (U.K.) Ltd | Manufacturing | 2020 |
| Angels Media Ltd | Information & communication | 2013 |
| Anima Balabio Ltd | Other services | 2023 |
| Animal ARK Ltd | Other services | 2021 |
| Animal Therapist Ltd | Professional & scientific | 2012 |
| Aninulo Properties Ltd | Real estate | 2023 |
| Anitech Consultancy Ltd | Professional & scientific | 2013 |
| Anjole Capital Limited | Professional & scientific | 2024 |
| Anml Ltd | Wholesale & retail | 2021 |
| Anna Enterprises Ltd | Real estate | 2020 |
| Anna Travel & School Services Ltd | Transport & logistics | 2015 |
| Anno Transport Ltd | Transport & logistics | 2017 |
| Ansa Care Limited | Administrative & support | 2017 |
| Ansacare 247 Ltd | Health & social care | 2024 |
| Ansh Property Development Limited | Real estate | 2012 |
| Anthony Morris Limited | Professional & scientific | 2009 |
| Antony & Moore Ltd | Wholesale & retail | 2024 |
| Antropy Ltd | Information & communication | 2008 |
| Anttechcs Ltd | Information & communication | 2023 |
| ANV Transport Ltd | Transport & logistics | 2025 |
| Anxiety Online Therapy Ltd | Health & social care | 2026 |
| Aobe Architectural Design Studio Ltd | Professional & scientific | 2025 |
| AOF Ltd | Arts & recreation | 2026 |
| Aogenix Ltd | Transport & logistics | 2025 |
| Aokca Limited | Professional & scientific | 2024 |
| AOL Ltd | Wholesale & retail | 2025 |
| AOP Logistics Ltd | Administrative & support | 2016 |
| AP Gatwick Limited | Transport & logistics | 2025 |
| Apex GAS and Heating Ltd | Construction | 2025 |
| Apex GAS and Plumbing Ltd. | Construction | 2017 |
| Apex Holidays Ltd | Administrative & support | 2025 |
| Apgecho Ltd | Health & social care | 2018 |
| Apheris Ltd | Wholesale & retail | 2022 |
| Apiary Bookkeeping Ltd | Professional & scientific | 2012 |
| Apnt (UK) Limited | Information & communication | 2024 |
| Apollo Hospitality (Highlands) Limited | Hospitality | 2025 |
| Apollo Hospitality (UHI) Limited | Hospitality | 2026 |
| Apollo Hospitality Limited | Hospitality | 2026 |
| Apostolic Assembly UK Ltd | Other services | 2019 |
| Appetite Avenue Ltd | Hospitality | 2026 |
| Apple Taxis and Cars Gatwick Limited | Transport & logistics | 2014 |
| Apples Property Ltd | Real estate | 2019 |
| Appleton Estates (UK) Ltd | Real estate | 2012 |
| Appliance Part NOW Ltd | Wholesale & retail | 2026 |
| Aprr Consultancy Ltd | Professional & scientific | 2020 |
| APS Expertise Ltd | Information & communication | 2014 |
| Aptiv (UK) Holdings Limited | Professional & scientific | 2009 |
| Aptiv Financial Investment Services (UK) Limited | Professional & scientific | 2012 |
| Aptiv Financial Services (UK) Limited | Professional & scientific | 2014 |
| Aptiv Global Holdings (UK) Limited | Professional & scientific | 2012 |
| Aptiv Holdfi (UK) Limited | Professional & scientific | 2011 |
| Aptiv Holdings (UK) Limited | Professional & scientific | 2011 |
| Aptiv Luxembourg Holdings (UK) Limited | Professional & scientific | 2015 |
| Aptiv Services UK Limited | Manufacturing | 1993 |
| APX Renovations Ltd | Construction | 2026 |
| AQ Trade Ltd | Wholesale & retail | 2024 |
| Aq-Io Limited | Professional & scientific | 2026 |
| AQS Consultancy and IT Services Limited | Information & communication | 2016 |
| Aquacoffeeshop Ltd | Wholesale & retail | 2022 |
| Aqualyft Ltd | Financial services | 2025 |
| Aquamaintain Consultancy Ltd | Agriculture & fishing | 2017 |
| Aquamaintain Ltd | Agriculture & fishing | 2012 |
| Aquaplumbing & Drainage Ltd | Construction | 2024 |
| Aquapro Bathrooms Ltd | Construction | 2026 |
| Aquarius Services Limited | Health & social care | 2015 |
| Aquastat Limited | Professional & scientific | 2017 |
| Aquatic Linen Service Limited | Other services | 2013 |
| Aquila Marine Limited | Transport & logistics | 2019 |
| Aquila Projects Ltd | Information & communication | 2023 |
| AR Administration Services Ltd | Administrative & support | 2023 |
| AR Driveways & Construction Ltd | Construction | 2026 |
| AR Global Consulting Ltd | Professional & scientific | 2018 |
| AR Pole Fitness Limited | Arts & recreation | 2021 |
| Arai Property Ltd | Real estate | 2023 |
| Aral Investments Limited | Real estate | 2024 |
| Araneo Consulting Ltd | Administrative & support | 2016 |
| Arborist Training & Consultancy Ltd | Agriculture & fishing | 2023 |
| Arbuda Limited | Wholesale & retail | 2013 |
| ARC Renshaw Consulting Limited | Administrative & support | 2022 |
| Arcadian Landscapes Ltd | Administrative & support | 2017 |
| Arcane Solutions Group Ltd | Administrative & support | 2026 |
| ARCH360 Limited | Information & communication | 2018 |
| Archers Court (Freehold) Limited | Real estate | 2002 |
| Archers Court Management Company Limited | Households | 1991 |
| Architectural Landscapes Ltd | Administrative & support | 2023 |
| Arctic Domestic & Commercial Cleaning Ltd | Administrative & support | 2025 |
| Arcwave Global Ltd | Extraterritorial | 2025 |
| Argus U.K. | | 1980 |
| Arik Empire Limited | Information & communication | 2023 |
| Arimed Health Ltd | Wholesale & retail | 2023 |
| ARK - Ituk Ltd | Information & communication | 2019 |
| ARK Interiors Limited | Other services | 2010 |
| ARK Investments Limited | Real estate | 2025 |
| ARK Law Limited | Professional & scientific | 2012 |
| ARK/8 Ltd | Wholesale & retail | 2022 |
| Arkley Estates Limited | Hospitality | 1970 |
| ARL Banton Ltd. | Water & waste | 2024 |