| 00648121 Limited | Professional & scientific | 1960 |
| 16 Citizen Media Works PVT (UK) Limited | Professional & scientific | 2001 |
| 1O1 Equator Ltd | Health & social care | 2010 |
| 1ST Choice Speakers UK Ltd | Arts & recreation | 2005 |
| 20/20 Project Management Limited | Professional & scientific | 2004 |
| 2HWEALTHCARE LLP | | 2002 |
| 3-10 Loakes Court Limited | Real estate | 2000 |
| 3B Hire and Servicing Limited | Administrative & support | 2006 |
| 3D Mechanical Innovation Limited | Professional & scientific | 2005 |
| 4MOST Consulting Ltd | Professional & scientific | 2025 |
| 55 Heyford Avenue Limited | Households | 2001 |
| 8 the Avenue NW6 Limited | Households | 1997 |
| A C M (UK) Ltd | Professional & scientific | 1995 |
| A P Team Limited | Other services | 2003 |
| A.& F.Howland(Wycombe)Limited | Manufacturing | 1927 |
| A.J.Fowler Limited | | 1962 |
| A.K. Accountancy Services Limited | Professional & scientific | 2002 |
| A.P.S. Engineering Limited | Manufacturing | 1984 |
| A.S.A.P. Domestic Appliance Services Limited | Other services | 2003 |
| A.S.T.P. Limited | Real estate | 2005 |
| A2 Records Limited | Information & communication | 2002 |
| Abacus Financial Management Services Limited | Real estate | 2007 |
| Abbmedia Solutions Ltd | Professional & scientific | 2024 |
| Abbotsbrook Estate Limited | Households | 2007 |
| ABK Decorations Ltd | Construction | 1996 |
| ABL (Holding) Limited | Professional & scientific | 1982 |
| Abysstideart Ltd | Wholesale & retail | 2025 |
| Accelerate Limited | Wholesale & retail | 1997 |
| Accentive Limited | Real estate | 2001 |
| Ace Locums Limited | Health & social care | 1995 |
| Ace World Foods Ltd | Manufacturing | 2021 |
| Action Heating Limited | Construction | 2004 |
| Active Accounting Limited | Professional & scientific | 2007 |
| AD Astra Education Ltd | Education | 2025 |
| Adams & Hicks Properties Limited | Real estate | 2024 |
| Adeleke Commercial Advisory Ltd | Professional & scientific | 2026 |
| Adsum Sport and Play Limited | Construction | 2017 |
| AF Carpentry Limited | Construction | 2022 |
| Afro Hair & Cosmetics Ltd | Wholesale & retail | 2004 |
| AH Accounting Limited | Professional & scientific | 2002 |
| Ahad Choudhury Foundation | Arts & recreation | 2007 |
| AIA Nundah Company | | 1991 |
| Aitoolboard Limited | Information & communication | 2025 |
| Ajmb Management Services Ltd | Professional & scientific | 2020 |
| Ajooni Investments Limited | Real estate | 2018 |
| AKL & TSL Ltd | Households | 2022 |
| Alakazam Ltd. | Information & communication | 1995 |
| Alan Boyd Productions Limited | Professional & scientific | 1980 |
| Albany Gate Residents' Association Limited | Households | 1971 |
| Alcan High Duty Extrusions Limited | Professional & scientific | 1913 |
| Alderbourne Landscapes Limited | Administrative & support | 2003 |
| Alexandra Dixon Interiors Limited | Professional & scientific | 1989 |
| Alfsware Limited | Hospitality | 1973 |
| Align Chemical Limited | Wholesale & retail | 2007 |
| ALL Occasions Ltd | Arts & recreation | 2000 |
| Allied Westminster Limited | Information & communication | 1997 |
| Almosa Limited | Real estate | 1995 |
| Alpha Omega Limited | Manufacturing | 1998 |
| Alphawave Limited | Information & communication | 1996 |
| Amari Family Ltd | Real estate | 2026 |
| Ambar Millennium Products Limited | Professional & scientific | 1999 |
| Amber Performance Limited | Extraterritorial | 2007 |
| Ambient Solutions Limited | Information & communication | 2002 |
| Amersham Double Glazing and Building Limited | Construction | 2006 |
| Amersham Plastics Limited | | 1969 |
| Amersham Properties Limited | Real estate | 1951 |
| AMG Holdings Limited | Professional & scientific | 1988 |
| Anamy Limited | Professional & scientific | 2003 |
| Andrew Milsom & Partners (Letting) Limited | Real estate | 2006 |
| Andrew Milsom & Partners Limited | Real estate | 1997 |
| Androv Limited | Wholesale & retail | 2003 |
| Anduff Car Wash Limited | Other services | 1970 |
| Anduff Holdings Limited | Real estate | 1970 |
| Angelface Limited | Administrative & support | 1997 |
| Antac Building Services Limited | Administrative & support | 2006 |
| Apex Automation Solutions Limited | Manufacturing | 1998 |
| Aplus Subc Limited | Professional & scientific | 2018 |
| Apmg-Australasia Limited | Extraterritorial | 2007 |
| Applied Process Limited | Administrative & support | 2007 |
| Apricot Penguin Limited | Information & communication | 2007 |
| Aqueous (Fitted Bathrooms) II Limited | Extraterritorial | 1999 |
| Aqueous Limited | Wholesale & retail | 1994 |
| Aralam Limited | Water & waste | 2004 |
| ARC Root Consulting Ltd | Information & communication | 2014 |
| Archer Technicoat Limited | Manufacturing | 1984 |
| Ardsmore Construction Services Limited | Construction | 2006 |
| Arktek Ltd | Information & communication | 2006 |
| Arrow Construction Services Limited | Construction | 2017 |
| Artistry Events | Arts & recreation | 2005 |
| Arun Property Company Limited | Construction | 2009 |
| Asasca Limited | Financial services | 2019 |
| Ascent Healthcare Holdings Limited | Financial services | 2026 |
| Ashbrook Fencing and Paving Ltd | Administrative & support | 2023 |
| Ashgrove Renovations Ltd | Households | 2021 |
| Askbus Ltd | Extraterritorial | 2014 |
| Aspen Media Limited | Administrative & support | 1994 |
| Astan Homes Limited | Real estate | 2018 |
| Astbury Consulting Services Ltd. | Professional & scientific | 2006 |
| Aston Heritage Limited | Wholesale & retail | 1994 |
| Aston Martin Lagonda Service Limited | Professional & scientific | 1993 |