| Alpha Homes and Interiors Limited | Wholesale & retail | 2016 |
| Alpha Recruitment Centre Limited | Administrative & support | 2018 |
| Alpha Sigma Limited | Professional & scientific | 2023 |
| Alqb Limited | Education | 2026 |
| Alright Ltd | Real estate | 2025 |
| Alsteno Ltd | Construction | 2026 |
| Altavia House RTM Company Limited | Households | 2026 |
| Althea Rose Ltd | Professional & scientific | 2022 |
| Alto Conveyancing Limited | Professional & scientific | 2026 |
| Altrek Ltd | Construction | 2025 |
| Altrumed UK Ltd | Administrative & support | 2026 |
| Alvand Communications Ltd | Professional & scientific | 2018 |
| Aly&Edy Logistics Ltd | Transport & logistics | 2026 |
| Alya Catering Ltd | Hospitality | 2023 |
| Alya Food Supply Ltd | Wholesale & retail | 2024 |
| Alyncasamaria Ltd | Transport & logistics | 2020 |
| AM Legacy Sports Consult Limited | Arts & recreation | 2023 |
| AM UK Cleaning & Maintenance Limited | Administrative & support | 2017 |
| AMA Ambassadeur Care Ltd | Health & social care | 2025 |
| AMA Ambassadeur Services Limited | Health & social care | 2019 |
| AMA Building Progress Ltd | Construction | 2024 |
| AMA Development Group Ltd | Real estate | 2023 |
| Amadeus Trans Ltd | Transport & logistics | 2018 |
| Amaivangu Limited | Health & social care | 2022 |
| Amandox Limited | Health & social care | 2025 |
| Amarissa Ltd | Real estate | 2022 |
| Amatod Medical Services Limited | Health & social care | 2023 |
| Amaze Electrical Ltd | Construction | 2020 |
| Amazing Assets Limited | Real estate | 2018 |
| Amazing Grace Consulting Ltd | Professional & scientific | 2026 |
| Amazing Incorporated Limited | Wholesale & retail | 2026 |
| Amazing Stars Childcare Services Ltd | Health & social care | 2022 |
| AMB Global Trade Finance Consultants Ltd | Professional & scientific | 2022 |
| Ambaal Traders Ltd | Hospitality | 2025 |
| Amber EM Limited | Professional & scientific | 2005 |
| Amber Path Trading Ltd | Wholesale & retail | 2025 |
| Amberley Place (Calne) Management Company Limited | Households | 2007 |
| Amconnections Ltd | Information & communication | 2025 |
| Amee Simpson Ltd | Information & communication | 2015 |
| Amehdi Limited | Wholesale & retail | 2022 |
| Amergin Partners Limited | Real estate | 2017 |
| American Logistics Ltd | Transport & logistics | 2026 |
| AMI (Herts) Limited | Construction | 2004 |
| AMI Systems (UK) Limited | Construction | 2010 |
| Amigos AD Vitam Limited | Wholesale & retail | 2024 |
| AMJ Ceilings Ltd | Construction | 2013 |
| AMJ Data Limited | Other services | 2020 |
| AMJ Renovations Ltd | Construction | 2022 |
| Amjoy Wellness Ltd | Health & social care | 2023 |
| Ammbes Saani (UK) Ltd. | Transport & logistics | 2016 |
| Amor Amor Ltd | Education | 2011 |
| Amos Oyebolu Medical Limited | Health & social care | 2023 |
| Amozidu Ltd | Health & social care | 2021 |
| AMP Networking Limited | Information & communication | 2010 |
| Amplified Learning Ltd | Education | 2022 |
| Amplify Life Ltd | Wholesale & retail | 2024 |
| Amplo Ltd | Construction | 2018 |
| Amran and Brothers Ltd | Hospitality | 2013 |
| Amremed Ltd | Health & social care | 2023 |
| Amwell Digital Ltd | Professional & scientific | 2024 |
| Amyris Limited | Extraterritorial | 1993 |
| AN Ideal Home Limited | Construction | 2017 |
| AN- NUR Agro Allied Ltd | Real estate | 2026 |
| AN2022 Limited | Hospitality | 2024 |
| ANA Recruitment Limited | Administrative & support | 2020 |
| Anae Medical Limited | Health & social care | 2025 |
| Anais Trans Ltd | Transport & logistics | 2014 |
| Analytics United Ltd | Information & communication | 2024 |
| Anamorava Coffee Shop Ltd | Hospitality | 2024 |
| Anaqor Limited | Wholesale & retail | 2016 |
| Anat-Elroi Global Limited | Health & social care | 2025 |
| Anca&Ale Cleaning Services Ltd | Administrative & support | 2025 |
| Anchorstack Ltd | Information & communication | 2026 |
| Anda Ltd | Wholesale & retail | 2011 |
| Andre and Aspen Limited | Wholesale & retail | 2024 |
| Andre and Aspen Properties Limited | Real estate | 2024 |
| Andre Logistic Services Ltd | Transport & logistics | 2023 |
| Andre Logistics & Distribution Limited | Transport & logistics | 2017 |
| Andrea Jade Limited | Health & social care | 2010 |
| Andreea Stoica Ltd | Health & social care | 2015 |
| Andrei Speed Ltd | Transport & logistics | 2019 |
| Andrius Construction 1 Limited | Construction | 2024 |
| Andrusca Limited | Construction | 2015 |
| Andy Roberts BJJ Limited | Education | 2011 |
| Andy's Angels Official Ltd | Wholesale & retail | 2020 |
| Anelest Ltd | Construction | 2023 |
| Angd Consulting Ltd | Professional & scientific | 2026 |
| Angel Gastro Care Ltd | Health & social care | 2025 |
| Angel Mews Management Limited | Households | 1998 |
| Angel Pilot UK Limited | Wholesale & retail | 2025 |
| Angelbarracks Limited | Transport & logistics | 2017 |
| Angeleyes Limited | Other services | 2025 |
| Angelic Finishes Ltd | Construction | 2024 |
| Angelic Quality Systems Ltd | Health & social care | 2003 |
| Angelica's World Ventures Ltd | Manufacturing | 2022 |
| Angels 2.0 Ltd | Arts & recreation | 2026 |
| Anghel Build Ltd | Construction | 2025 |
| Angieama Limited | Information & communication | 2023 |
| Anglia Occupational Health Ltd | Health & social care | 2012 |
| Anglian Environmental Limited | Administrative & support | 2008 |