| AJC Attachments Limited | Wholesale & retail | 2025 |
| Ajhs Anywhere Limited | Professional & scientific | 2011 |
| Akrus Limited | Health & social care | 2010 |
| AL Hamra Supermarket Limited | Wholesale & retail | 2014 |
| Aladdins Balti Limited | Hospitality | 2015 |
| Albany Aesthetics Ltd | Health & social care | 2019 |
| Albany Cottages Limited | Real estate | 1997 |
| Alden Solar Energy Solutions Ltd | Construction | 2022 |
| Aldwinckles Coffee House Ltd | Hospitality | 2018 |
| Aleconbury Ltd | Professional & scientific | 2020 |
| Alexander Transport Limited | Transport & logistics | 2026 |
| Alice Jones Impact Consulting Limited | Professional & scientific | 2012 |
| Alishan Tandoori Wisbech Limited | Hospitality | 2025 |
| Alistructures Limited | Construction | 2010 |
| ALL 1 Tribe Limited | Arts & recreation | 2016 |
| ALL About Trees MH Ltd | Administrative & support | 2025 |
| ALL Fibre Solutions Limited | Information & communication | 2022 |
| ALL Figured OUT Limited | Professional & scientific | 2011 |
| Allan Access Platform Services Limited | Professional & scientific | 2009 |
| Alloway Management Services Ltd | Administrative & support | 2025 |
| Allsaints Hairdressing Ltd | Other services | 2018 |
| Allsaints Hairdressing Stamford Ltd | Other services | 2024 |
| Alma J Limited | Real estate | 2022 |
| Almeida Properties Ltd | Real estate | 2021 |
| Alpha DLT Ltd | Professional & scientific | 2021 |
| Alpha Electrical and Property Limited | Construction | 2017 |
| Alpine Cadence Ltd | Administrative & support | 2009 |
| Alsager Projects Ltd | Real estate | 2011 |
| Alto Management (U.K.) Limited | Hospitality | 1987 |
| Alto Travel Limited | Construction | 2012 |
| Altus MEP Ltd | Professional & scientific | 2025 |
| Aluminium Direct Limited | Wholesale & retail | 2005 |
| AM Care & Consultancy Ltd | Health & social care | 2026 |
| AM Winter Ltd | Administrative & support | 2022 |
| Amanda Swain Naabic Services Limited | Professional & scientific | 2015 |
| Amazing Tipis Ltd | Other services | 2016 |
| Ambassador College. | Education | 1980 |
| Amberclear Limited | Financial services | 1998 |
| Amberstone Land and Property Ltd | Real estate | 2023 |
| Amml Properties Limited | Real estate | 2018 |
| Amour Adventures Ltd | Administrative & support | 2024 |
| Ampersand LDN Limited | Manufacturing | 2018 |
| Ample Grid Holdings Limited | Real estate | 2018 |
| ANB Design Ltd | Education | 2021 |
| Ancarite Limited | Professional & scientific | 2020 |
| Ancma Limited | Education | 2025 |
| Andrew Kirk Consultants Limited | Education | 2013 |
| Andrews Matting Solutions Limited | Administrative & support | 2011 |
| Angealio Ltd | Professional & scientific | 2006 |
| Animal Therapy Media Limited | Information & communication | 2015 |
| Anisa (GB) Limited | Hospitality | 2011 |
| ANN Gover Property Holdings Ltd | Households | 2025 |
| Annabelle Forde Creates Ltd | Information & communication | 2023 |
| Annabelle Forde Ltd | Administrative & support | 2023 |
| Annapurna Nutrition and Wellbeing Ltd | Extraterritorial | 2020 |
| Antonio Giorgi Ltd | Wholesale & retail | 2007 |
| Anxa Ltd | Wholesale & retail | 2025 |
| AP Club Limited | Wholesale & retail | 2026 |
| AP Matters Ltd | Education | 2024 |
| AP Research Ltd | Professional & scientific | 2014 |
| Apace Finance Ltd | Professional & scientific | 2020 |
| APC Gidoc Limited | Health & social care | 2012 |
| Apograph Data Systems Limited | Real estate | 1998 |
| Apograph Limited | Information & communication | 2011 |
| Apple Tree Communications (ATC) Ltd | Professional & scientific | 2015 |
| Applebee Marketing Limited | Professional & scientific | 2019 |
| Appletree Law Ltd. | Professional & scientific | 2019 |
| Apricity Three Ltd | Professional & scientific | 2022 |
| Apricus Holdings Limited | Professional & scientific | 2021 |
| Aptech (Powder Systems) Limited | Professional & scientific | 1994 |
| AR Tyler Ltd | Administrative & support | 2022 |
| ARC Partnership Ltd | Construction | 2020 |
| Archrise Limited | Wholesale & retail | 1995 |
| Archrise Property Limited | Real estate | 2020 |
| Archway Health Limited | Health & social care | 2014 |
| Arctics Limited | Administrative & support | 2004 |
| Arete Contractors Limited | Construction | 2010 |
| ARJ Management Services Ltd | Professional & scientific | 2020 |
| ARK Construction Limited | Real estate | 2001 |
| ARK Solar Limited | Energy | 2026 |
| Arkel Computer Services Limited | Manufacturing | 1982 |
| Arklight Consulting Ltd | Administrative & support | 2013 |
| Armcandy BAG Co Ltd | Wholesale & retail | 2022 |
| Armourgeddon Photography Limited | Professional & scientific | 2012 |
| Aroni Limited | Financial services | 2020 |
| Arraminta Limited | Wholesale & retail | 2014 |
| Arrow Professional Services Limited | Financial services | 2006 |
| Art Printed Ltd | Manufacturing | 2024 |
| Arteks Textiles UK Limited | Wholesale & retail | 2023 |
| Arts Fresco Events Ltd | Arts & recreation | 2013 |
| Arts Fresco Limited | Professional & scientific | 2014 |
| ARW Finance Limited | Administrative & support | 2022 |
| Asbeth Associates Ltd | Real estate | 2022 |
| Asbh Developments Ltd | Construction | 2025 |
| Ascension Consulting Ltd | Other services | 2021 |
| Asgard Commercial Holdings Ltd | Construction | 2025 |
| Asgardian Holdings Ltd | Financial services | 2025 |
| ASH Building Services Consultants Limited | Professional & scientific | 2003 |
| Ashton Marketing Holdings Ltd | Financial services | 2018 |
| Ashton Marketing Services Ltd | Wholesale & retail | 2000 |