| Aiten Finance Limited | Professional & scientific | 2014 |
| Ajax Insurance Association Limited(The) | Financial services | 1972 |
| Ajility Ltd. | Professional & scientific | 2007 |
| AJS Waddon Ltd | Real estate | 2021 |
| AKM Systems Limited | Information & communication | 1991 |
| Akni Retail Ltd | Wholesale & retail | 2026 |
| Aksara Services Ltd | Wholesale & retail | 2024 |
| Aksess Ltd | Professional & scientific | 1989 |
| Alabet Consultancy Ltd | Professional & scientific | 2004 |
| Alacrity Integrated Ltd | Information & communication | 2007 |
| Alaga Limited | Professional & scientific | 1996 |
| Alan Bettin Limited | Construction | 2001 |
| Alan Draper Limited | | 1983 |
| Albany House Residents' Company Limited | Households | 1982 |
| Albany Resources Limited | Administrative & support | 2016 |
| Albion Childes Limited | Professional & scientific | 1993 |
| Albion Hospitality (Oxshott) Ltd | Hospitality | 2025 |
| Albion Windows and Conservatories Limited | Construction | 1996 |
| Albone Jewellers (Croydon) Ltd | Wholesale & retail | 2005 |
| Albright Surveyors Limited | Professional & scientific | 1993 |
| Alchem Holdings Limited | Professional & scientific | 1970 |
| Alcheme Wellness Ltd | Wholesale & retail | 2025 |
| Alco Drilling Company Limited | | 1983 |
| Alco-Tech UK Ltd | Manufacturing | 2025 |
| Aldeburgh House Management Company Limited | Hospitality | 2006 |
| Alees Services UK Limited | Arts & recreation | 2019 |
| Alexander Fraser Developments Limited | Construction | 1963 |
| Alexander Properties (London) Limited | Construction | 1997 |
| Alexandra (Kingston) Management Limited | Households | 1979 |
| Alexandra Management Solutions Ltd | Professional & scientific | 2014 |
| Alexandra SPV Limited | Real estate | 2025 |
| Alexias Consulting Limited | Administrative & support | 2004 |
| Alfa Laval Limited | Manufacturing | 1923 |
| Alfaland Limited | Real estate | 1984 |
| Alfred James & Co. Solicitors LLP | | 2007 |
| Alfve Limited | Wholesale & retail | 2012 |
| Algorem Analytics Ltd | Professional & scientific | 2020 |
| ALI Developments (UK) Limited | Real estate | 2020 |
| ALI Memorial Centre (AMC) | Health & social care | 2003 |
| Aligned and Unlimited Consulting Ltd | Professional & scientific | 2012 |
| Alinus Couriers Ltd | Transport & logistics | 2018 |
| Alisha (UK) Limited | Real estate | 2003 |
| Alisha Express Ltd | Hospitality | 2018 |
| Aljeros Import & Export Company Limited | | 1980 |
| Alkatraz Media Ltd | Professional & scientific | 2015 |
| ALL About Flooring Limited | Wholesale & retail | 2002 |
| ALL Ceramics Limited | Health & social care | 1968 |
| ALL Digital Services Limited | Information & communication | 2004 |
| ALL Options Limited | Manufacturing | 2007 |
| ALL Purpose Builders Limited | | 1978 |
| Allamand Consulting Limited | Administrative & support | 2016 |
| Allamin & Co. Limited | | 1976 |
| Allan Wilson Music Limited | Arts & recreation | 2006 |
| Allen (Fencing) Limited | Construction | 1950 |
| Allete Trading Limited | Professional & scientific | 2006 |
| Allexavior Limited | Education | 2025 |
| Allhallows Fish Bar Ltd | Hospitality | 2026 |
| Alliance Care Services Ltd | Education | 2005 |
| Allianz Engineering Inspection Services Limited | Professional & scientific | 2005 |
| Allianz Equity Investments Limited | Extraterritorial | 1987 |
| Allianz Insurance PLC | Financial services | 1905 |
| Allianz Properties Limited | Real estate | 1986 |
| Allied Global Tobacco Ltd | Manufacturing | 2005 |
| Allied Marketing Limited | Professional & scientific | 1999 |
| Allsorts Inflatables Limited | Arts & recreation | 2003 |
| Allspin Limited | Other services | 2025 |
| Allstudios Limited | Information & communication | 2007 |
| Allswell Care Services Limited | Health & social care | 1996 |
| Alma Lane Management Company Limited | Households | 1996 |
| Alpha Estates (Elmers END) Limited | Real estate | 2005 |
| Alpha Estates (London) Limited | Real estate | 1996 |
| Alpha Europe Contracting Limited | | 1988 |
| Alpha Online Systems Limited | | 1982 |
| Alpha-Echo Three-Five Limited | Information & communication | 2006 |
| Alphachem Limited | Real estate | 1979 |
| Alphaland (UK) Limited | Real estate | 1999 |
| Alps FS (Management and Compliance) Limited | Administrative & support | 1997 |
| Alston Computer Solutions Limited | Information & communication | 1998 |
| Altaego Limited | Professional & scientific | 2003 |
| Altera Aesthetics Ltd | Extraterritorial | 2023 |
| Alton (U.K.) Limited | Administrative & support | 1981 |
| Alton Accommodation Limited | Hospitality | 2025 |
| Alvandy Ltd | Health & social care | 2026 |
| Alves Limited | Construction | 2008 |
| Alves&Son’S Properties Limited | Construction | 2024 |
| Alys Catering Limited | Real estate | 1975 |
| Amafi Solutions Ltd | Professional & scientific | 2007 |
| Amalgamated Security Ltd. | Administrative & support | 2007 |
| Amanda George Production Buyer Limited | Information & communication | 2013 |
| Amazing Grace Ministries (Kingdom Centre) Ltd. | Other services | 2005 |
| Amazingclean Limited | Wholesale & retail | 2006 |
| Ambassador Electrical Systems Limited | Wholesale & retail | 1995 |
| Amber Locum Services Limited | Professional & scientific | 2003 |
| Amber Residential Lettings Ltd | Real estate | 2005 |
| Amber-Tech Electrical Services Limited | Construction | 2001 |
| Ambernectar Ltd | Extraterritorial | 2013 |
| Ambledash Limited | Households | 2007 |
| Amcs Performance Consulting Limited | Other services | 2016 |
| American Line Limited | Manufacturing | 1996 |
| Ames Brisley Accounting Ltd | Professional & scientific | 2016 |