| AS Good AS New Outlet Limited | Wholesale & retail | 2025 |
| AS Real Estate Management Limited | Real estate | 2026 |
| ASA Carpet & Flooring Limited | Wholesale & retail | 2023 |
| Ascea Ltd | Other services | 2020 |
| Ascendea Limited | Information & communication | 2025 |
| Asgaard Ltd | Professional & scientific | 2021 |
| Ashborn Rose Ltd | Extraterritorial | 2022 |
| Ashflame Cardington Limited | Real estate | 2017 |
| Ashflame Chantry Limited | Real estate | 2020 |
| Ashflame Harrogate Limited | Real estate | 2018 |
| Ashflame Properties Limited | Real estate | 1993 |
| Ashwell Associates Limited | Information & communication | 2014 |
| Asianmade (Manufacturing) Limited | Professional & scientific | 2006 |
| Asis Solutions Limited | Information & communication | 2009 |
| ASK Electrix UK Ltd | Construction | 2022 |
| ASO Solutions Ltd | Construction | 2025 |
| ASP Electrical Installation Services Ltd | Construction | 2021 |
| ASP Property Group Ltd | Real estate | 2024 |
| Aspecto Power Engineering UK Limited | Professional & scientific | 2024 |
| Association of NHS Charities | Other services | 2019 |
| Assured Aviation Services Limited | Other services | 2015 |
| Assured Group Holdings Limited | Professional & scientific | 2007 |
| Assured Group Investments Limited | Wholesale & retail | 2016 |
| Assured Group Limited | Wholesale & retail | 1996 |
| Assured Human Resources Limited | Other services | 2001 |
| Assured Valeting Holdings Limited | Administrative & support | 2003 |
| Asteroid Global Limited | Financial services | 2023 |
| Asthill Investments Ltd | Real estate | 2021 |
| Asthill Properties Ltd | Real estate | 2021 |
| Aston Martin Financial Services Limited | Extraterritorial | 2009 |
| Aston Martin Holdings (UK) Limited | Professional & scientific | 2007 |
| Aston Martin Investments Limited | Professional & scientific | 2007 |
| Aston Martin Lagonda Group Limited | Professional & scientific | 1981 |
| Aston Martin Lagonda Limited | Manufacturing | 1975 |
| Aston Martin Lagonda Pension Trustees Limited | Professional & scientific | 1976 |
| Aston Martin Works Limited | Wholesale & retail | 2009 |
| Astronomer Data Ltd | Information & communication | 2019 |
| AT & TF Holdings Limited | Financial services | 2021 |
| Atelier-Ace London, Ltd | Real estate | 2012 |
| Athena Court Management Company Limited | Households | 2007 |
| Athena Family Investments | Financial services | 2024 |
| Athena House Management Company Limited | Households | 2007 |
| Athena New Tech Ltd | Wholesale & retail | 2020 |
| Atherton Media Group Limited | Financial services | 2025 |
| Athium Limited | Information & communication | 2005 |
| Athwal Healthcare Ltd | Wholesale & retail | 2021 |
| Atmaana Business Consulting Limited | Professional & scientific | 2010 |
| Atomchat Limited | Professional & scientific | 2025 |
| Attensi Limited | Other services | 2017 |
| Attman Ltd | Professional & scientific | 2025 |
| Attwell & SON Ltd | Agriculture & fishing | 2022 |
| ATY Automotive & Industrial Components (UK) Limited | Water & waste | 1990 |
| AUA Property Limited | Real estate | 2025 |
| Auburn Creative Limited | Information & communication | 2003 |
| Auctoro Recruitment Limited | Administrative & support | 2019 |
| Audhalis Ltd | Wholesale & retail | 2022 |
| Audience Loop Limited | Information & communication | 2014 |
| Audio 88 Limited | Information & communication | 2023 |
| AUM Prop Ltd | Real estate | 2024 |
| Aura Fine Art Ltd | Wholesale & retail | 2020 |
| Aura Triathlon Coaching Ltd | Professional & scientific | 2017 |
| Aureus Capital Limited | Professional & scientific | 2009 |
| Aurora Holdco Limited | Administrative & support | 2021 |
| Aurora Production Music Limited | Information & communication | 2018 |
| Austbuild Ltd | Construction | 2014 |
| Aut-Tech Automation Limited | Wholesale & retail | 2009 |
| Auto Clear Vision Ltd | Wholesale & retail | 2025 |
| Auto Converse Limited | Information & communication | 2022 |
| Auto Electrical Solutions (2011) Limited | Wholesale & retail | 2011 |
| Auto Platforms Ltd | Information & communication | 2019 |
| Autoart Styling Limited | Wholesale & retail | 2009 |
| Autohydrate Limited | Other services | 2022 |
| Automally Ltd | Information & communication | 2025 |
| Automobility Solutions Limited | Wholesale & retail | 2024 |
| Automotive Performance Development Ltd | Professional & scientific | 2019 |
| Autotrack Installations Ltd | Manufacturing | 2019 |
| AUX Capital Ltd | Financial services | 2025 |
| Avamae Investments 1 Limited | Real estate | 2022 |
| Avan International Ltd | Construction | 2021 |
| Avanete Ltd | Wholesale & retail | 2023 |
| Avant Wholesale Ltd | Wholesale & retail | 2020 |
| Aveling & Porter Limited | Manufacturing | 2003 |
| Aveling-Barford Limited | Manufacturing | 2003 |
| Avenue Electrical (Warwickshire) Limited | Construction | 2014 |
| Avenue Pattern Co.Limited | Manufacturing | 1963 |
| Aviationtrim Ltd | Manufacturing | 2023 |
| AVK Foods Private Limited | Hospitality | 2023 |
| Avon (Midlands) Limited | Financial services | 2018 |
| Avon Building Ltd | Construction | 2025 |
| Avon Oak Properties Ltd | Construction | 2023 |
| Avon Oak Supported Accommodation Ltd | Real estate | 2026 |
| Avon Signs Limited | Administrative & support | 2010 |
| Avon Studios Ltd | Manufacturing | 2022 |
| Avon Valley Indoor Bowls Club Limited | Arts & recreation | 2014 |
| AXB Hub Ltd | Information & communication | 2025 |
| Axis & Globe 2023 Limited | Financial services | 2023 |
| Axis & Globe Transport Limited | Transport & logistics | 2026 |
| AXIS3 Design Limited | Professional & scientific | 2006 |
| Axon Potential Foundation | Health & social care | 2022 |
| Ayas Properties Ltd | Real estate | 2026 |