| Able Data Services Ltd | Professional & scientific | 2001 |
| Ablebay Limited | Households | 2001 |
| Abmetech Limited | Professional & scientific | 2004 |
| Abnet Limited | Information & communication | 1997 |
| Abroadacre Limited | Households | 2000 |
| Absb Properties Limited | Real estate | 2011 |
| Acadian Properties Limited | Real estate | 2003 |
| Access & Video Solutions Limited | Administrative & support | 2002 |
| Access Control Services Limited | Other services | 1993 |
| Acclaim Recruitment Limited | Administrative & support | 2003 |
| Accountancy & Book-Keeping Services Limited | Professional & scientific | 1984 |
| Accountancy AID Limited | Professional & scientific | 1997 |
| Ace Construction Work Ltd | Construction | 2019 |
| Ace N ABI Ltd | Information & communication | 2007 |
| Achall Driving School Limited | Education | 2017 |
| Achieve Villa Limited | Professional & scientific | 2012 |
| Ackers (Chemists) Limited | Wholesale & retail | 1954 |
| ACL Homes Plus Limited | Hospitality | 1998 |
| ACM Property Services UK Limited | Construction | 2007 |
| Acms Services Limited | Information & communication | 2004 |
| Acredia Limited | Professional & scientific | 1993 |
| Acronim Holdings Ltd | Financial services | 2024 |
| ACS Engraving Limited | Other services | 2004 |
| Actabilityuk Ltd | Professional & scientific | 2021 |
| Action Topcare Services UK Ltd | Construction | 2021 |
| Actionlake | | 1997 |
| Active Care Living Limited | Health & social care | 2025 |
| Active Career Transition Limited | Extraterritorial | 2005 |
| Active Immigration Solutions Limited | Professional & scientific | 2005 |
| Active Value Limited | Financial services | 2002 |
| Active Vehicle Consultants Limited | Professional & scientific | 1995 |
| Adams Educational Services Limited | Education | 2015 |
| Adas Smile Ltd | Health & social care | 2022 |
| ADD Value Accountancy Limited | Professional & scientific | 2007 |
| Addept Computer Services Limited | Information & communication | 1987 |
| Addison Mortgage Services Limited | Extraterritorial | 2003 |
| Addit Bookkeeping Services Ltd | Professional & scientific | 2006 |
| Addo Construction Ltd | Construction | 2007 |
| Adedapo Alagbe Ltd | Health & social care | 2022 |
| Adelaide House Management Company Limited | Real estate | 2000 |
| Adeoye Ventures Ltd | Health & social care | 2022 |
| ADM Computer Services Limited | Information & communication | 1992 |
| ADM United Kingdom Investments L.P. | | 1993 |
| Admiral Signs London Ltd. | Construction | 2007 |
| Admirals Reach Management Company Limited | Households | 1987 |
| Adrian Steele Pianos Limited | Arts & recreation | 2003 |
| ADS Technical Services Ltd | Construction | 2002 |
| Advacom Limited | Information & communication | 1998 |
| Advance Construction (Medway) Limited | Construction | 1984 |
| Advance Telecom (UK) Limited | Information & communication | 2004 |
| Advanced Bird and Pest Control Limited | Administrative & support | 2003 |
| Advent Electrical (Kent) Limited | Construction | 2002 |
| Adventure Racing Limited | Arts & recreation | 2007 |
| Advocacy Consultancy Ltd | Professional & scientific | 2015 |
| Adyan Spice Limited | Hospitality | 2022 |
| ADZ Platform Limited | Information & communication | 2021 |
| Aegean Trading Limited | Wholesale & retail | 2015 |
| AER Plumbing&Electrical Ltd | Construction | 2025 |
| Aero Limited | Manufacturing | 2000 |
| Aerofoil Design and Management Limited | Administrative & support | 2009 |
| Aesvani Limited | Wholesale & retail | 2024 |
| Aether Motion Capital Ltd | Wholesale & retail | 2024 |
| AFC Trading Limited | Construction | 1978 |
| Africa Products Limited | Wholesale & retail | 1996 |
| Afritrans Limited | Administrative & support | 2001 |
| AG Bright Cleaning Company Ltd | Administrative & support | 2025 |
| Agalma Ltd | Financial services | 2025 |
| AGB Connect Ltd | Information & communication | 2025 |
| AGE Concern Sandwich Centre for the Retired | Health & social care | 2003 |
| Aggarwal & Co Limited | Real estate | 1990 |
| AGH Haulage Limited | Information & communication | 2006 |
| Agincourt Investments Limited | Real estate | 2007 |
| AGP Management Consulting Ltd | Construction | 2019 |
| Ahead Start Consulting Limited | Professional & scientific | 2003 |
| AIM Commercial Cleaning Limited | Administrative & support | 1979 |
| AIM Mechanical Services Limited | Construction | 1992 |
| AIM Systems Limited | Information & communication | 1995 |
| AIM Technical Services Limited | Construction | 2003 |
| Airpack 2000 Installations Limited | Administrative & support | 1998 |
| Airparks Services (Birmingham) Limited | Other services | 1994 |
| Airparks Services (East Midlands) Limited | Extraterritorial | 1993 |
| Airports 24-7 Ltd | Transport & logistics | 2005 |
| AJ Davies Properties Ltd | Real estate | 2022 |
| Aj's Care Services Ltd | Health & social care | 2019 |
| AJA Kent Ltd | Financial services | 2020 |
| Ajacent Investments Ltd | Hospitality | 2020 |
| AJH Accountancy Ltd | Professional & scientific | 2003 |
| Ajlbs Ltd | Professional & scientific | 2015 |
| AK Barbers Hextable Ltd | Other services | 2025 |
| AK Optical Limited | Wholesale & retail | 2016 |
| Akaditi Limited | Information & communication | 2011 |
| AKG Contracting Services Ltd | Real estate | 2012 |
| AL Fresco Comforts Limited | Extraterritorial | 2001 |
| AL Hera Ltd | Education | 2019 |
| AL Home Improvements 19 Ltd | Construction | 2025 |
| AL Wahab Properties Ltd | Real estate | 2024 |
| Alan Morton Management Services Limited | Professional & scientific | 1997 |
| Alandale Building & Fit OUT Limited | Construction | 2006 |
| Alanya Ltd | Construction | 2017 |
| Alarming Events Limited | Other services | 2004 |