| Ascot Autoclaves Ltd. | Manufacturing | 1994 |
| Ascot Land Limited | Real estate | 2016 |
| Ascot Painting Contractors Ltd. | Construction | 2003 |
| Ascot Place Facilities Ltd | Households | 2006 |
| Ascot Stairs Ltd | Construction | 2020 |
| Ascotash Ltd | Extraterritorial | 2024 |
| Ashfieldheating Ltd | Construction | 2021 |
| Ashfin Limited | Other services | 2013 |
| Ashni PVT Ltd | Administrative & support | 2016 |
| Ashridge Aesthetics Ltd | Other services | 2022 |
| Ashridge Manor Farm Nursery Limited | Wholesale & retail | 2017 |
| Ashton Consultancy Ltd. | Professional & scientific | 2003 |
| Ashwood Court (Knaphill) Limited | Households | 2005 |
| ASK Enterprise AK Limited | Professional & scientific | 2016 |
| ASK Productions Limited | Information & communication | 2020 |
| ASK Properties AK Limited | Real estate | 2019 |
| Aslan Construction and Development Ltd | Construction | 2010 |
| Asmaa Attia Consultancy Limited | Professional & scientific | 2026 |
| Asmr Holdings Limited | Professional & scientific | 2015 |
| ASP Limited | Real estate | 2019 |
| Aspcc Limited | Professional & scientific | 2025 |
| Aspects Court (RTM) Company Limited | Households | 2009 |
| Aspire Design & Build Limited | Construction | 2025 |
| Aspire Fireplaces Limited | Construction | 2020 |
| Aspire Life Coaching Ltd | Health & social care | 2020 |
| Aspn Holdings Limited | Real estate | 2016 |
| Asset 5 Group Limited | Financial services | 2024 |
| Asset Arts Production Services Ltd | Information & communication | 2019 |
| Asset Recovery Consultants Limited | Administrative & support | 2009 |
| Assist Logistics Ltd. | Construction | 2015 |
| Associated Gardeners and Property Services Limited | Administrative & support | 2008 |
| Association of Consulting Actuaries Limited | Other services | 2016 |
| Association of Professional Pension Trustees Limited | Other services | 2012 |
| Assured People Support Limited | Health & social care | 2026 |
| Aston House Ventures Limited | Real estate | 2022 |
| Astrale Luxury Limited | Wholesale & retail | 2025 |
| Astranova Solutions Ltd | Information & communication | 2024 |
| Astrawave Systems Ltd | Wholesale & retail | 2026 |
| Astro Air Express Limited | Transport & logistics | 1991 |
| Athena Therapy Services Ltd | Health & social care | 2025 |
| Athenaeum Education Ltd | Education | 2023 |
| Athleta Olympia Ltd | Arts & recreation | 2023 |
| Athleticademix Ltd | Education | 2019 |
| ATK Group Limited | Construction | 2023 |
| Atlacare Ltd | Information & communication | 2026 |
| Atlantis Trading Corp Limited | Wholesale & retail | 2023 |
| Atlas Clinical Intelligence Limited | Information & communication | 2026 |
| Atlas Global Education Ltd | Education | 2026 |
| ATM Machine Tools Limited | Manufacturing | 1992 |
| Atomik Wraps Ltd | Wholesale & retail | 2025 |
| Atoz Consulting Ltd | Professional & scientific | 2022 |
| Attilio D'Alberto Ltd | Health & social care | 2015 |
| Attollowest Limited | Real estate | 2024 |
| Au's BRO Limited | Other services | 2022 |
| Auburn Court Freehold Ltd | Households | 2016 |
| Audus Interiors Ltd | Wholesale & retail | 2010 |
| Augusta Life Sciences UK Limited | Manufacturing | 2025 |
| AUM Capital Investments Ltd | Real estate | 2026 |
| Auralisx Ltd | Professional & scientific | 2025 |
| Aureus Scientific Limited | Professional & scientific | 2019 |
| Aurika Consulting Limited | Public administration | 2025 |
| Austella Ltd | Manufacturing | 2014 |
| Austin Ellis Beau Limited | Extraterritorial | 2022 |
| Authentic Flavors Ltd | Hospitality | 2024 |
| Auto Advisor Limited | Wholesale & retail | 2018 |
| Auto Campers Ltd | Wholesale & retail | 2020 |
| Auto Ignite Ltd | Information & communication | 2023 |
| Auto Imaging Limited | Information & communication | 2016 |
| Autocross (Properties) Limited | Real estate | 2002 |
| Automated LAB Systems Limited | Information & communication | 2009 |
| Automation Test Consultants Limited | Information & communication | 2013 |
| Autopilot Group Limited | Information & communication | 2023 |
| Autotune Car Sales Ltd | Professional & scientific | 2026 |
| Autumn UK Investments Ltd | Construction | 2017 |
| AV Accountants Limited | Professional & scientific | 2010 |
| AV Houses Limited | Real estate | 2022 |
| AVA Building & Property Maintenance Ltd | Construction | 2022 |
| Avaero Ltd | Education | 2019 |
| Avancraft Design &Building Ltd | Construction | 2018 |
| Avanya Ltd | Professional & scientific | 2016 |
| AVD Appoint Ltd | Administrative & support | 2019 |
| Aveborne Limited | Professional & scientific | 2004 |
| Avenue Property Limited | Real estate | 2017 |
| Avery Hatton Limited | Professional & scientific | 2018 |
| Avia Technique Limited | Manufacturing | 2002 |
| Aviation and Retail Management Ltd. | Other services | 1997 |
| Avicena Medical Limited | Health & social care | 2025 |
| Avicenna London Ltd | Wholesale & retail | 2012 |
| Avion Systems Consulting Ltd. | Professional & scientific | 2013 |
| Avishaan Limited | Professional & scientific | 2025 |
| Avpm Group Limited | Financial services | 2023 |
| AW Automotive Limited | Wholesale & retail | 2026 |
| Aware Developments Ltd | Construction | 2014 |
| Aware Organisation Ltd | Professional & scientific | 2019 |
| Aware Properties Ltd | Real estate | 2017 |
| AWC Automotive Ltd | Wholesale & retail | 2025 |
| Awdy Ventures Ltd. | Professional & scientific | 2024 |
| AWS Electrical Contractors Ltd | Construction | 2023 |
| Axiom Accounts Ltd | Professional & scientific | 2019 |
| AXLR8 Limited | Information & communication | 2000 |