| Agile Technology Solutions Limited | Information & communication | 2009 |
| Agnostec Limited | Information & communication | 2026 |
| Ahmed Groceries Ltd | Wholesale & retail | 2025 |
| AI Recruit Ltd | Information & communication | 2023 |
| AIM Altus Ltd | Information & communication | 2024 |
| Air Concept Refrigeration Limited | Manufacturing | 2014 |
| Air Premier Cars Berkshire Ltd | Transport & logistics | 2018 |
| Air Premier Properties Ltd | Real estate | 2002 |
| Airline Components International Limited | Manufacturing | 1987 |
| Airsoft Armoury UK Ltd | Wholesale & retail | 2023 |
| Airtasker UK Limited | Administrative & support | 2017 |
| Ajcs Moments Limited | Professional & scientific | 2018 |
| AJH Highway Services Ltd | Construction | 2023 |
| Ak&M Consultancy Limited | Information & communication | 2025 |
| Ak&M Properties Ltd | Real estate | 2021 |
| Akisan Properties Investments Ltd | Real estate | 2021 |
| Aksharyogi Security System Ltd | Construction | 2019 |
| Al-Hamd Investments Ltd | Real estate | 2023 |
| Alan Buckley Limited | Professional & scientific | 2012 |
| Alan Lane Ltd | Information & communication | 2025 |
| Alarmatech Ltd | Administrative & support | 2024 |
| Alatronic Limited | Administrative & support | 2016 |
| Albemarle Street Ltd | Construction | 2020 |
| Alcestis Limited | Professional & scientific | 2006 |
| Alchemy BLD Limited | Real estate | 2016 |
| Alda Landscapes Limited | Administrative & support | 2006 |
| Aldhelm Limited | Real estate | 2021 |
| Aldworth Developments Limited | Wholesale & retail | 2018 |
| Alexander Harrison Limited | Administrative & support | 2012 |
| Alexon Real Estates Ltd | Real estate | 2021 |
| Algo Properties Limited | Administrative & support | 1994 |
| Alia Solutions Ltd | Agriculture & fishing | 2019 |
| Alice Land Services Ltd | Administrative & support | 2026 |
| Alinea Nutrition Ltd | Education | 2025 |
| Alison Buchanan Associates Ltd | Professional & scientific | 2010 |
| Aliva Engineering Limited | Construction | 2007 |
| Aliva UK Limited | Construction | 2002 |
| Alkus Consulting Ltd | Information & communication | 2022 |
| ALL About ME Marquees & Events Ltd | Other services | 2012 |
| ALL About the Data Limited | Extraterritorial | 2008 |
| ALL Aspect Garden Design & Build Ltd | Administrative & support | 2013 |
| ALL Garden Services (Newbury) Ltd | Administrative & support | 2024 |
| ALL Possible Care Ltd | Health & social care | 2019 |
| Allen's of Tadley Limited | Wholesale & retail | 2011 |
| Alliance Entrance Systems Ltd | Construction | 2021 |
| Allinc Property Services Ltd | Construction | 2026 |
| Allium Investments Ltd | Real estate | 2020 |
| Alma Care Training Limited | Education | 2010 |
| Alma Consultants Ltd | Professional & scientific | 2020 |
| Alpha Bravo Marketing Insight Limited | Professional & scientific | 2015 |
| Alphamates Limited | Administrative & support | 1988 |
| Altaria Consulting Ltd | Professional & scientific | 2025 |
| Althea Soft Ltd | Information & communication | 2021 |
| Alto Technologies Limited | Other services | 2022 |
| Alumini Holdings Limited | Financial services | 1994 |
| Alvarador Limited | Information & communication | 2025 |
| Alwayson Business Limited | Extraterritorial | 2013 |
| Alwaysup International Ltd | Health & social care | 2026 |
| AM Hair Limited | Other services | 2011 |
| Amadeus International Limited | Administrative & support | 1993 |
| Amanda Goldthorpe Ltd | Information & communication | 2017 |
| Amanda Salter Design Ltd | Information & communication | 2013 |
| Amarone Bar and Restaurant Towcester Limited | Hospitality | 2024 |
| Amba Consulting & Analytics Limited | Professional & scientific | 2013 |
| Amber Green Clinics Ltd | Health & social care | 2024 |
| Amber Telecoms Ltd | Information & communication | 2026 |
| Amberforge Limited | Professional & scientific | 1996 |
| Amberjack EBT Trustee Limited | Professional & scientific | 2021 |
| Amberjack Global Limited | Information & communication | 2000 |
| Amberleigh Cleaning Services Limited | Administrative & support | 2000 |
| Ambertronic Limited | Manufacturing | 2017 |
| Ambitionabm Ltd | Professional & scientific | 2010 |
| Ambrig Building Ltd | Construction | 2016 |
| AMD Construction Ltd | Construction | 2024 |
| Amethyst Ankh Limited | Information & communication | 2022 |
| Amicus Networks Limited | Information & communication | 2011 |
| Amies Capital Limited | Professional & scientific | 2016 |
| AMJ Auto Services Ltd | Wholesale & retail | 2014 |
| AMK Electrical and Maintenance Ltd | Manufacturing | 2018 |
| AMM Landscapes Limited | Professional & scientific | 2025 |
| Ammoni Consulting Limited | Administrative & support | 2017 |
| Amoh Limited | Health & social care | 2014 |
| Amore Bar Limited | Hospitality | 2024 |
| Amore Hungerford Ltd | Hospitality | 2025 |
| Amos Management Ltd | Construction | 2024 |
| Ampere Electrical Services Limited | Construction | 2018 |
| Ampha Limited | Information & communication | 2016 |
| Amplify Media Ltd | Professional & scientific | 2009 |
| AMR Financial Management Limited | Financial services | 1992 |
| AMS Plumbing Supplies Holdings Limited | Extraterritorial | 2018 |
| AMS Plumbing Supplies Limited | Extraterritorial | 1998 |
| ANA Cleaning Ltd | Administrative & support | 2025 |
| Ancile Cyber Security Limited | Information & communication | 2018 |
| Andrew Gowing Installations Ltd | Construction | 2016 |
| Andrew Hawkins Limited | Other services | 2006 |
| Andrew Wright IT Consultancy Limited | Administrative & support | 2013 |
| Andy Compton Plumbing and Heating Services Limited | Other services | 2011 |
| Angel Flooring Agencies Ltd | Wholesale & retail | 2018 |
| Angetech Consultants Limited | Information & communication | 2008 |
| ANH Nails Limited | Other services | 2019 |