| Alconbury Aesthetics Ltd | Health & social care | 2022 |
| Alconbury and Brampton Innovative Healthcare Ltd | Health & social care | 2021 |
| Alconbury Packing Solutions Limited | Real estate | 2015 |
| Alconbury Weald Community Association C.I.C. | Arts & recreation | 2024 |
| Alec Hirst Ltd | Professional & scientific | 2011 |
| Alento Ltd | Professional & scientific | 2017 |
| Alexander Dalton Limited | Professional & scientific | 2008 |
| Alexander House (Sheringham) Management Limited | Real estate | 2004 |
| Alexandra Dawson Wellness Ltd | Arts & recreation | 2010 |
| Alfieh Ltd | Manufacturing | 2023 |
| Alfred Energy Limited | Energy | 2021 |
| Alfresco Dining Company Limited | Wholesale & retail | 2020 |
| Aliaxis Holdings UK Limited | Financial services | 2000 |
| Aliaxis UK Limited | Manufacturing | 1983 |
| Alinafe Ltd | Transport & logistics | 2022 |
| Alistair Davis Regulatory Consultancy Limited | Administrative & support | 2009 |
| ALL Around Cleaners Ltd | Administrative & support | 2026 |
| ALL Court Clothing Co Ltd | Wholesale & retail | 2026 |
| ALL Day Building Ltd | Construction | 2018 |
| ALL in One Building Limited | Construction | 2008 |
| ALL Natural Soap Co Limited | Manufacturing | 2013 |
| ALL Saints Estates Ltd | Real estate | 2016 |
| ALL Undercover Marquees Ltd | Hospitality | 2005 |
| Alloy Ambulance Limited | Wholesale & retail | 2015 |
| Allsafe Perioperative Limited | Health & social care | 2014 |
| Alltac Labels Ltd | Manufacturing | 2024 |
| Alltech Office Solutions Limited | Manufacturing | 2022 |
| Allways Garage Services Limited | Wholesale & retail | 2003 |
| Alnetuk Limited | Professional & scientific | 2009 |
| Alng Properties Ltd | Real estate | 2020 |
| Alpha & Ace Holdings Ltd | Manufacturing | 2024 |
| Alpha Roofing & Guttering Ltd | Construction | 2026 |
| Alpha Trucking Ltd | Transport & logistics | 2018 |
| Alphadrugs Limited | Wholesale & retail | 2015 |
| Alpheus Environmental Limited | Administrative & support | 1990 |
| Altaris Advisory Limited | Professional & scientific | 2026 |
| Altx Therapeutics Limited | Professional & scientific | 2025 |
| Aluco Aluminium Limited | Manufacturing | 2017 |
| Aluco Limited | Financial services | 2017 |
| Alzure Environmental Services Limited | Water & waste | 2015 |
| AM Rendering Ltd | Construction | 2024 |
| Amaizing Skills Ltd | Construction | 2020 |
| Amanda Orchard Consultancy Ltd | Professional & scientific | 2025 |
| Amandas Driving Instruction Ltd | Education | 2024 |
| Amar Convenience Store Ltd | Wholesale & retail | 2022 |
| AMB Bookkeeping & Accountancy Services Ltd. | Professional & scientific | 2017 |
| AMB Concrete Ltd | Administrative & support | 2013 |
| Ambito Partners Ltd | Professional & scientific | 2020 |
| Ambler Mann Holdings Limited | Administrative & support | 2025 |
| Ambury Developments Limited | Construction | 2001 |
| AMD Services Ltd | Construction | 2026 |
| Amedeni Ltd | Transport & logistics | 2016 |
| Ameoz Group Ltd | Manufacturing | 2017 |
| Ameya Decor Ltd | Wholesale & retail | 2026 |
| Amiens Ltd | Construction | 2021 |
| Amina Technologies Limited | Manufacturing | 1998 |
| Amira EDU Ltd | Health & social care | 2015 |
| AML Logix Limited | Other services | 2023 |
| Amlani Consultants Limited | Professional & scientific | 2023 |
| Amma Vanta Ltd | Manufacturing | 2025 |
| AMN Garage Services and Equipment Limited | Manufacturing | 2002 |
| AMO-01 Pharma Limited | Professional & scientific | 2021 |
| AMO-06 Pharma Limited | Professional & scientific | 2021 |
| Amphibian Apparel Limited | Other services | 2019 |
| Amphibian Assets Limited | Real estate | 2016 |
| Amphibian Clothing Limited | Manufacturing | 2019 |
| Amphibian Commercial Assets Limited | Real estate | 2023 |
| Amphibian Scaffolding Limited | Construction | 2008 |
| Ampliforth Consulting Limited | Information & communication | 2025 |
| Amplify NOW Limited | Professional & scientific | 2019 |
| AMS Safety Services Ltd | Public administration | 2019 |
| Amsel Investments Limited | Real estate | 2002 |
| Amvee Investments Limited | Wholesale & retail | 2019 |
| Amy's Acro Ltd | Arts & recreation | 2015 |
| Amybowman Ltd | Health & social care | 2022 |
| Amycable HR Solutions Ltd | Professional & scientific | 2025 |
| Amymersh Limited | Other services | 2020 |
| Anderson Centre Management (Huntingdon) Limited | Real estate | 1996 |
| Andora Klean Limited | Other services | 2005 |
| Andrea Bullshead Ltd | Other services | 2022 |
| Andrew Jones Direct Limited | Manufacturing | 2011 |
| ANG Tools Ltd | Wholesale & retail | 2026 |
| Angarun Limited | Information & communication | 2017 |
| Angela Mann Recruitment Ltd | Administrative & support | 2023 |
| Anglia Healthcare & Mobility Ltd | Health & social care | 2012 |
| Anglia Interiors Limited | Wholesale & retail | 1975 |
| Anglia Property Group Ltd | Real estate | 2021 |
| Anglian Venture Holdings Limited | Professional & scientific | 2007 |
| Anglian Water (Osprey) Financing PLC | Administrative & support | 2010 |
| Anglian Water Direct Limited | Financial services | 1997 |
| Anglian Water Group Pension Trustee Limited | Other services | 2019 |
| Anglian Water International Holdings Limited | Administrative & support | 1986 |
| Anglian Water International Limited | Administrative & support | 1992 |
| Anglian Water Services Financing PLC | Administrative & support | 2001 |
| Anglian Water Services Holdings Limited | Professional & scientific | 2001 |
| Anglian Water Services Limited | Water & waste | 1989 |
| Anglian Water Services UK Parent Co Limited | Financial services | 2018 |
| Anglian Window Cleaning Ltd | Administrative & support | 2014 |
| Angloria Studios Ltd | Information & communication | 2026 |
| Animal Insights Consultancy Ltd | Professional & scientific | 2026 |