| Alphax Technology Co., Ltd | Information & communication | 2025 |
| Alpherantz Ltd | Manufacturing | 1987 |
| Alpium Limited | Financial services | 2025 |
| Alps Software Ltd | Information & communication | 2020 |
| Alquist Consulting Limited | Information & communication | 2003 |
| Alsalch for Trading Ltd | Wholesale & retail | 2024 |
| Alski Ltd | Hospitality | 2012 |
| Alstan Co (UK) Ltd | Other services | 2004 |
| Alta Innovation Ltd | Professional & scientific | 2024 |
| Altai Design Ltd | Wholesale & retail | 2021 |
| Altdorff Ltd | Wholesale & retail | 2022 |
| Alte Ukeig | Administrative & support | 1992 |
| Altemislab Ltd | Professional & scientific | 2018 |
| Alterity Therapeutics UK Limited | Professional & scientific | 2004 |
| Alterix Limited | Professional & scientific | 2003 |
| Alternewenergy Ltd | Extraterritorial | 2021 |
| Altham Property Solutions Limited | Construction | 2025 |
| Altimim LLP | | 2024 |
| Altior Consulting Ltd | Professional & scientific | 2024 |
| Altium UK Limited | Wholesale & retail | 1994 |
| Altj @ Cambridge COM Ltd | Wholesale & retail | 2016 |
| Alto Cumulus (Environmental) Solutions Limited | Professional & scientific | 2021 |
| Altra Solutions Ltd | Professional & scientific | 2025 |
| Altrex Engineering Ltd | Professional & scientific | 2022 |
| Alturas Ltd | Information & communication | 2003 |
| Altwaly Company Ltd | Wholesale & retail | 2024 |
| Aluzion Blinds Limited | Manufacturing | 2019 |
| Alveire Group Limited | Professional & scientific | 2024 |
| Alveon Pre-Consulting Services Ltd | Administrative & support | 2025 |
| Alviq Properties Limited | Real estate | 2020 |
| Always Fire Safety Ltd | Professional & scientific | 2022 |
| Alyazori Trading Co., Ltd. | Administrative & support | 2016 |
| Alzheimer's Brain Bank UK | Health & social care | 2006 |
| Alzheimer's Research Trading Limited | Health & social care | 1999 |
| Alzheimer's Research UK | Health & social care | 1998 |
| AM Aero Tech&Tools Ltd | Administrative & support | 2025 |
| AM Branding Ltd | Professional & scientific | 2020 |
| AM Heating Services Limited | Manufacturing | 2015 |
| AM Import and Export Co., Ltd | Wholesale & retail | 2025 |
| AM Law Limited | Administrative & support | 2021 |
| AM Smart Limited | Administrative & support | 2006 |
| AMA Dablam SET Carpentry Ltd | Construction | 2025 |
| Amadeus & Angels Seed Fund | | 2006 |
| Amadeus BI LP | | 2020 |
| Amadeus Capital GP LLP | | 2013 |
| Amadeus Capital Limited | Real estate | 2000 |
| Amadeus Capital Partners (Nominee) Ltd | Professional & scientific | 2003 |
| Amadeus Capital Partners Limited | Financial services | 1997 |
| Amadeus Creative Limited | Wholesale & retail | 2019 |
| Amadeus EI LP | | 2009 |
| Amadeus EII LP | | 2011 |
| Amadeus Eiii LP | | 2015 |
| Amadeus EV LP | | 2022 |
| Amadeus GI LP | | 2019 |
| Amadeus HI LP | | 2013 |
| Amadeus I | | 1997 |
| Amadeus II 'a' | | 2000 |
| Amadeus II 'B' | | 2000 |
| Amadeus II 'C' | | 2000 |
| Amadeus III | | 2005 |
| Amadeus IT Limited | Information & communication | 2007 |
| Amadeus IV Digital Prosperity LP | | 2013 |
| Amadeus IV Early Stage Fund a LP | | 2013 |
| Amadeus IV Early Stage Fund B LP | | 2013 |
| Amadeus IV Growth LP | | 2015 |
| Amadeus IV Velocity Fund LP | | 2014 |
| Amadeus JI LP | | 2013 |
| Amadeus Mobile Seed Fund | | 2001 |
| Amadeus Partners Limited | Financial services | 1998 |
| Amadeus PI LP | | 2013 |
| Amadeus Rsef LP | | 2013 |
| Amadeus TI LP | | 2015 |
| Amadeus V Growth Fund LP | | 2023 |
| Amadeus V Latin America Sustainable Growth Fund LP | | 2021 |
| Amadeus V Technology Fund LP | | 2018 |
| Amadeus VI Technology Fund LP | | 2023 |
| Amadora Baby Ltd | Wholesale & retail | 2016 |
| Amagufa Solutions Limited | Professional & scientific | 2015 |
| Amalive Limited | Professional & scientific | 2023 |
| Amanah Enterprise Ltd | Wholesale & retail | 2020 |
| Amaniglobal Ltd | Other services | 2017 |
| Amantys Power Electronics Ltd. | Professional & scientific | 2015 |
| Amarew Limited | Professional & scientific | 2019 |
| Amariah Gastroenterology Services Limited | Health & social care | 2016 |
| Amarok Audio Ltd | Manufacturing | 2025 |
| Amauta Limited | Professional & scientific | 2024 |
| Amavanti Limited | Professional & scientific | 2016 |
| Amazing Grazing Foods Ltd | Professional & scientific | 2013 |
| Amazing Salads Ltd | Other services | 2017 |
| Amber Court Management (2007) Limited | Households | 2007 |
| Amber Lodge Guest House LLP | | 2002 |
| Amber Oak Holdings Limited | Education | 2026 |
| Amberframe Holdings Limited | Real estate | 2010 |
| Amberframe Limited | Construction | 1986 |
| Amberley Residents Association Limited | Real estate | 1986 |
| Ambience Spaces Ltd | Real estate | 2021 |
| Ambient Media 360 Ltd | Manufacturing | 2020 |
| Ambigram Consulting Ltd | Professional & scientific | 2022 |
| Ambika Homes Limited | Real estate | 2021 |
| Ambrit Enterprises Limited | Wholesale & retail | 2011 |