| Arts Wellness Collective Limited | Health & social care | 2023 |
| Artsmart School of Art Limited | Education | 2005 |
| Artsmartuk Ltd. | Arts & recreation | 2010 |
| Artus Capital Limited | Real estate | 2020 |
| Arxis Capital Limited | Professional & scientific | 2025 |
| Asas Services Limited | Professional & scientific | 2016 |
| ASH Managing Investments Ltd | Construction | 2021 |
| ASH Peterson Food Company Limited | Hospitality | 2020 |
| Ashberry Physiotherapy Ltd | Health & social care | 2021 |
| Ashcroft & Portman Chauffeurs Ltd | Transport & logistics | 2015 |
| Ashcroft House (Staines) Building Management Company Limited | Households | 2023 |
| Ashcroft Place (Staines) Management Company Limited | Households | 2023 |
| Ashfield Special Needs Limited | Administrative & support | 2008 |
| Ashton Cardale Limited | Professional & scientific | 2021 |
| ASL21 Ltd | Administrative & support | 2018 |
| ASM Auto Recycling Ltd. | Wholesale & retail | 1983 |
| ASM Metal Recycling Ltd. | Water & waste | 1967 |
| ASM Skip Hire Limited | Extraterritorial | 2003 |
| ASM Waste Services Limited | Extraterritorial | 2003 |
| Asobi Ventures Limited | Information & communication | 2025 |
| Aspectu Ltd | Professional & scientific | 2018 |
| Asperger's Syndrome Foundation | Health & social care | 2001 |
| Aspyering Reality Limited | Real estate | 1994 |
| Assure Property Buyers Ltd | Extraterritorial | 2023 |
| Astec Management Limited | Professional & scientific | 1999 |
| Aston House Management Company Limited | Real estate | 2005 |
| Astus Financial Planning Ltd | Financial services | 2001 |
| Astute Designs Ltd | Professional & scientific | 2024 |
| Astute Medical Education Limited | Administrative & support | 2017 |
| AT Rhodes Holdings Limited | Information & communication | 2023 |
| Ataline Advisers Limited | Financial services | 2024 |
| Atek Technology Limited | Administrative & support | 2001 |
| ATG Investments UK Limited | Financial services | 2017 |
| Atlantic Management Centre International Limited | Administrative & support | 2003 |
| Attapoll Holdings Ltd | Financial services | 2021 |
| Attarewards Holdings Ltd | Financial services | 2026 |
| Audax Capital Ltd | Professional & scientific | 2009 |
| Audvech Ltd | Information & communication | 2024 |
| Augustine Investment Holdings Limited | Real estate | 2024 |
| Aussie in Exile Limited | Professional & scientific | 1987 |
| Austin Catelinet Limited | Real estate | 1967 |
| Austin Healey Limited | Professional & scientific | 1998 |
| Avamax LLP | | 2010 |
| Avant Healthcare Global Ltd | Health & social care | 2015 |
| Avant Healthcare Services Limited | Health & social care | 2011 |
| Avante Luxe Healthcare Ltd | Health & social care | 2025 |
| Avanti Design (Bucks) Limited | Professional & scientific | 2002 |
| Avenue Road Freehold Limited | Households | 2011 |
| Avercet Limited | Extraterritorial | 2009 |
| Avida Consultancy Ltd. | Professional & scientific | 2016 |
| Avighna Business Solutions Limited | Administrative & support | 2020 |
| Avitus Consulting Limited | Professional & scientific | 2011 |
| Avitus Group of Companies Limited | Professional & scientific | 2011 |
| Avon Cottage Investments Limited | Professional & scientific | 2018 |
| AW Risk Solutions Limited | Financial services | 2025 |
| Awake: the Conscious Meditation Practice Ltd | Other services | 2022 |
| Axial Evolution Limited | Construction | 2025 |
| Ayaraa Properties LLP | | 2026 |
| Aylesbury Auto Salvage Limited | Extraterritorial | 2004 |
| Aylesbury Secondary Metals Limited | Extraterritorial | 2004 |
| Aylesbury Skip Hire Limited | Professional & scientific | 1997 |
| Azenby Ltd. | Information & communication | 2012 |
| Aztec Control Services Limited | Construction | 2022 |
| Azteq Data Ltd | Information & communication | 2025 |
| Azteq Group Ltd | Information & communication | 2019 |
| Azteq Limited | Professional & scientific | 2009 |
| B D Aesthetics Ltd | Health & social care | 2013 |
| B G C (1991) Limited | Arts & recreation | 1991 |
| B.Bryan Electrical Ltd | Construction | 2025 |
| B6 Developments Limited | Construction | 2011 |
| Babel Street Rosette Ltd | Wholesale & retail | 2012 |
| Backyard Cinema Ltd | Information & communication | 2014 |
| Bahkubo Limited | Wholesale & retail | 2021 |
| Bailey Capital Limited | Financial services | 2017 |
| Bains Growth Limited | Professional & scientific | 2026 |
| Balanced Fractional Solutions Limited | Professional & scientific | 2025 |
| Balform Holdings Limited | Financial services | 2020 |
| Balform Limited | Manufacturing | 1978 |
| Balstone Estates Limited | Construction | 1973 |
| Banana Plant Company Limited | Extraterritorial | 2013 |
| Banana Plant Limited | Extraterritorial | 2013 |
| Banana Studios Limited | Arts & recreation | 2014 |
| Banxtra Consultants Limited | Administrative & support | 2014 |
| Barakunan UK Ltd | Information & communication | 2022 |
| Barenaturals Ltd | Wholesale & retail | 2012 |
| Bargrand General Trading Co. Limited | Real estate | 1978 |
| Barkin'Beauties of Beaconsfield Ltd | Other services | 2025 |
| Barlet-Batada Limited | Professional & scientific | 2015 |
| Basement Trading Limited | Hospitality | 2020 |
| Bayaphambili Limited | Real estate | 2023 |
| BCK Consultants International Limited | Professional & scientific | 2013 |
| BDK Supplies Ltd | Wholesale & retail | 2021 |
| Beacon House Property Limited | Real estate | 2004 |
| Beacon Wines Limited | Wholesale & retail | 2016 |
| Beaconsfield 1 Stop Solution Limited | Manufacturing | 2024 |
| Beaconsfield Authentic Spice Limited | Hospitality | 2024 |
| Beaconsfield Beauty Lounge Ltd | Other services | 2024 |
| Beaconsfield Bridge Club Ltd | Education | 2019 |
| Beaconsfield Country Estate Agents Limited | Real estate | 2021 |
| Beaconsfield Educational Trust Limited | Education | 1962 |