| Amakk Properties Limited | Real estate | 2020 |
| Ambassador (York) Management Company Limited | Households | 2004 |
| Ambassador Square Management Ltd | Households | 2021 |
| Amber Assets Limited | Health & social care | 2005 |
| Amber Buildings Limited | Construction | 2006 |
| Amber Care Limited | Health & social care | 2004 |
| Amber Company Secretaries Limited | Households | 2005 |
| Amber Development (Bros) Limited | Real estate | 2017 |
| Amber Enterprise Group Limited | Financial services | 2022 |
| Amber Estate Management Limited | Real estate | 2005 |
| Amber Management (Land and Estates) Limited | Households | 2010 |
| Amber Wharf Management Company Limited | Households | 2007 |
| Ambition Investments Ltd | Financial services | 2019 |
| AMC Run Projects Limited | Professional & scientific | 2015 |
| Amerco Electrical Distributors Limited | Wholesale & retail | 1999 |
| AMG Construction Services Limited | Construction | 2022 |
| Amgwaterproofing Limited | Construction | 2016 |
| AMH Scaffolding Ltd | Construction | 2022 |
| Amilah Consulting Limited | Information & communication | 2002 |
| AML Properties Limited | Real estate | 2013 |
| Amniky Services Ltd | Professional & scientific | 2024 |
| AMO Social Ltd | Professional & scientific | 2023 |
| AMP5 Ltd | Water & waste | 2010 |
| Ampfield (Management Company) Limited | Households | 2004 |
| Amrat Specialist Biohazard Limited | Administrative & support | 2026 |
| Amwell Kitchens Limited | Manufacturing | 2006 |
| Amwell Street Garage Limited | Wholesale & retail | 2009 |
| AMY Gallagher Coaching Ltd | Arts & recreation | 2015 |
| AN Tech & IT Limited | Information & communication | 2026 |
| Anatolia Cafe & Restaurant Ltd | Hospitality | 2018 |
| Anchor Quay Management Company Limited | Households | 2006 |
| Anderson Richards & Co. Limited | Wholesale & retail | 1936 |
| Andrew Macintosh Furniture Limited | Manufacturing | 1994 |
| Andrew MAY & Leanne MAY Ltd | Extraterritorial | 2016 |
| Andrew Pearson Partnership Ltd | Administrative & support | 2013 |
| Andromedia Ltd | Other services | 2011 |
| Anelay Building & Conservation (North West) Limited | Construction | 2015 |
| Anelay Building & Conservation Limited | Construction | 2013 |
| Angel Electrics Limited | Construction | 2018 |
| Angel Medical Care Ltd. | Health & social care | 2019 |
| Anglian Accident Repair Centres Limited | Administrative & support | 2009 |
| Anglo African Merchants Limited | | 1980 |
| Animated Design Limited | Manufacturing | 2016 |
| Anko the Best Windows Limited | Construction | 2011 |
| Anna Williamson Limited | Arts & recreation | 2007 |
| Another View Counselling Limited | Health & social care | 2022 |
| ANT Lite Ltd | Information & communication | 2018 |
| ANT Telecommunications Holdings Limited | Professional & scientific | 2005 |
| Anthony Lettings Limited | Real estate | 2011 |
| Anyimage Ltd | Other services | 2018 |
| AOB Security Ltd | Administrative & support | 2025 |
| Apex LI Ltd | Construction | 2026 |
| APG Bathrooms Ltd | Construction | 2024 |
| APG Property Investment Ltd | Real estate | 2026 |
| Aphelion Networks Limited | Information & communication | 2017 |
| Aphrodite Hair Products Limited | Extraterritorial | 1991 |
| Applegate (Sittingbourne) Management Company Limited | Households | 2022 |
| Appletree Court Management Limited | Households | 1989 |
| Appligence Limited | Information & communication | 2010 |
| Apsley (Hemel Hempstead) Management Company Limited | Households | 2002 |
| AQ Consultancy Ltd | Professional & scientific | 2024 |
| Aqua Wealth Management Limited | Financial services | 2012 |
| Aquacam Ltd | Professional & scientific | 2022 |
| Aquilae Search Partners Ltd | Administrative & support | 2023 |
| ARC Resolutions Ltd | Professional & scientific | 2013 |
| Arcam Properties Limited | Real estate | 2017 |
| Arcam Resources Limited | Administrative & support | 2009 |
| Ardent Consulting Ltd | Professional & scientific | 2023 |
| ARE YOU Safe GAS Ltd | Extraterritorial | 2017 |
| Arena Management Botley Road Limited | Households | 2005 |
| Arex Monitoring Ltd | Hospitality | 2019 |
| Argent Street "E" Management Limited | Real estate | 1987 |
| Argo Credit Management Limited | Professional & scientific | 2019 |
| Aries ADP Limited | Professional & scientific | 2018 |
| ARK23 Ltd | Information & communication | 2023 |
| ARK23 Property Ltd | Real estate | 2025 |
| Art Cleaning Services Limited | Administrative & support | 2020 |
| Artelectrico Limited | Wholesale & retail | 2021 |
| Artisans of Mexico Ltd | Wholesale & retail | 2015 |
| AS Builders (Broxbourne) Limited | Construction | 2014 |
| AS Electricians Ltd | Construction | 2022 |
| Asaf Produce Limited | Agriculture & fishing | 2014 |
| Ascot (Berkshire) Developments Limited | Construction | 2008 |
| ASH Meadows Management Company Limited | Real estate | 2019 |
| ASH Vale (Hampton Hargate) Management Company Limited | Households | 2003 |
| Ashbourne Insurance Services (Hoddesdon) Limited | Financial services | 1993 |
| Ashbourne Insurance Services Limited | Financial services | 2001 |
| Ashdown Place (Uckfield) Residents Company Limited | Households | 2010 |
| Ashdown Vale Management Company (Barnham) Limited | Real estate | 2016 |
| Ashes Enterprises Ltd | Education | 2020 |
| Ashfield Grange (Hemingbrough) Management Company Limited | Households | 2003 |
| Ashfield Nursery Limited | Agriculture & fishing | 2014 |
| Ashingdon Gardens (Block E) Management Company Limited | Households | 1994 |
| Ashlen Limited | Real estate | 2018 |
| Ashmount Court Management Limited | Households | 2005 |
| Ashmount Hill Management Company Limited | Households | 2012 |
| Ashore Cloud Limited | Information & communication | 2022 |
| Ashtons Scaffolding Limited | Construction | 2023 |
| Ashurst Inhaled Consulting Limited | Professional & scientific | 2025 |
| ASK Removals Limited | Transport & logistics | 2024 |