| Artan Investments Ltd | Administrative & support | 2023 |
| Artemisia Investments Limited | Real estate | 2025 |
| Arteon Technology Limited | Wholesale & retail | 2024 |
| Arterberry Developments Ltd | Construction | 2023 |
| Artezen UK Ltd | Professional & scientific | 2025 |
| Artificial Vision Intelligence Limited | Information & communication | 2024 |
| Artisan Building Services Ltd | Construction | 2025 |
| Artistic Caves Limited | Arts & recreation | 2025 |
| Artists and Artworks Limited | Arts & recreation | 2010 |
| Arts Home Official Construction Ltd | Construction | 2021 |
| ARU Asset Limited | Real estate | 2020 |
| ARU Asset Management Limited | Real estate | 2019 |
| ARU Property Holdings Limited | Real estate | 2015 |
| Arundel House (Eastbourne) Ltd | Households | 2005 |
| AS Heating & Plumbing (Surrey) Ltd | Construction | 2024 |
| Asapraj Consulting Ltd | Information & communication | 2011 |
| Asari.Io Limited | Administrative & support | 2018 |
| ASB Catering Limited | Hospitality | 2026 |
| Asbestaura Ltd | Construction | 2025 |
| Ascendant Limited | Administrative & support | 2003 |
| Ascension Training Ltd | Arts & recreation | 2016 |
| Ascent Loft Conversions Ltd | Construction | 2015 |
| Ascough & Associates - Consulting Engineers Limited | Professional & scientific | 1991 |
| Ashdown Place (Ewell) Management Company Limited | Households | 2002 |
| Ashlone Wharf Marine Limited | Manufacturing | 2023 |
| Ashmeadow Projects Limited | Professional & scientific | 2024 |
| Ashmn Holdings Limited | Financial services | 2023 |
| Ashmn Homes Ltd | Real estate | 2019 |
| Ashmn Investments Limited | Real estate | 2019 |
| Ashreed P.L.C. | Water & waste | 1989 |
| Ashtead Chiropractic Limited | Health & social care | 2005 |
| Ashtead Construction Limited | Construction | 2009 |
| Ashtead Sports Club Limited | Arts & recreation | 1928 |
| Ashtech Fitness Ltd | Other services | 2026 |
| Ashton (Residential) Limited | Real estate | 2017 |
| Ashton Developments Limited | Construction | 2012 |
| Ashurst Close Leatherhead ( Freehold) Limited | Households | 2016 |
| Ashwick Business Solutions Limited | Financial services | 2023 |
| Ashwood Place (Ascot) Management Company Limited | Households | 2004 |
| ASK X Management Consultants Ltd | Professional & scientific | 2023 |
| Askanthonyai Ltd | Information & communication | 2025 |
| ASM Consulting Ltd | Professional & scientific | 2025 |
| Asnr Investments Ltd | Real estate | 2025 |
| Aspect Land Management Ltd | Agriculture & fishing | 2024 |
| Aspect Nature Reserve Limited | Agriculture & fishing | 2025 |
| Aspen Healthcare Limited | Health & social care | 1997 |
| Aspen Leasing Limited | Administrative & support | 1985 |
| Aspice Consulting Limited | Professional & scientific | 2020 |
| Aspire Marketing Limited | Administrative & support | 2010 |
| Assist Facilities Management Ltd | Construction | 2024 |
| Assure Consulting (Middle East) Ltd | Professional & scientific | 2018 |
| Assure Dental Laboratory Ltd | Health & social care | 2024 |
| Aster and Wilde Ltd | Other services | 2017 |
| Aston Court Residents Company Limited | Households | 2000 |
| Asymilate Limited | Wholesale & retail | 2002 |
| AT Home Market Limited | Wholesale & retail | 2025 |
| Atar Studios Limited | Information & communication | 2020 |
| Atar Productions Limited | Information & communication | 2020 |
| Atecon Limited | Professional & scientific | 2016 |
| Atelier Bespoke Cabinetry Ltd | Manufacturing | 2022 |
| ATF Brighton Ltd | Arts & recreation | 2026 |
| ATF Property Holdings Ltd | Real estate | 2023 |
| ATF Worthing Ltd | Arts & recreation | 2009 |
| Athena Wealth Planning Limited | Professional & scientific | 2014 |
| ATK Energy EU Limited | Professional & scientific | 2005 |
| Atkins Pension Trustee Limited | Extraterritorial | 2009 |
| Atkinsréalis (GB) Holdings Limited | Professional & scientific | 2017 |
| Atkinsréalis (GBL) Limited | Professional & scientific | 2014 |
| Atkinsréalis (WS) Limited | Professional & scientific | 1985 |
| Atkinsréalis ATK Investments Limited | Administrative & support | 2002 |
| Atkinsréalis ATK Limited | Administrative & support | 2014 |
| Atkinsréalis Co. Ltd. | Professional & scientific | 2013 |
| Atkinsréalis Consultancy Services Limited | Administrative & support | 2010 |
| Atkinsréalis International Holdings Limited | Administrative & support | 2007 |
| Atkinsréalis PPS Holdings Limited | Administrative & support | 1994 |
| Atkinsréalis PPS Limited | Professional & scientific | 1988 |
| Atkinsréalis Rail & Transit Limited | Professional & scientific | 1995 |
| Atkinsréalis Rail & Transit Verification Limited | Professional & scientific | 2003 |
| Atkinsréalis Rail Limited | Professional & scientific | 1971 |
| Atkinsréalis UK International Limited | Administrative & support | 1973 |
| Atlantic Landscapes Ltd | Administrative & support | 2007 |
| Atlas Care Solutions Ltd | Health & social care | 2015 |
| Atlas Compliance Management Ltd | Extraterritorial | 2024 |
| Atmaca Ltd | Wholesale & retail | 2022 |
| Atmos Tech Limited | Real estate | 2026 |
| Atms Lettings Ltd | Real estate | 2026 |
| Atomic ANT Limited | Information & communication | 2008 |
| Atthman Limited | Health & social care | 2025 |
| Attomas Ltd | Construction | 2009 |
| Attwater Racing Limited | Arts & recreation | 2008 |
| Attwood and Binsted Limited | Information & communication | 1897 |
| Atull Ltd | Professional & scientific | 2007 |
| ATW Carpentry & Building Ltd | Manufacturing | 2026 |
| Audio Visual Resource Ltd | Construction | 2025 |
| Audiogradeuk Limited | Information & communication | 2021 |
| Audiolite Limited | Wholesale & retail | 1981 |
| Augustine Court Management Limited | Households | 2004 |
| Augustine Court Tenants Association Limited | Households | 2007 |
| Aurayu Limited | Information & communication | 2025 |
| Auriol Laundrette (UK) Ltd | Other services | 2025 |