| Advanced Precision Southern Limited | Real estate | 2003 |
| Advanced Roof Testing Ltd | Construction | 2020 |
| Advantage Air Systems Limited | Energy | 1994 |
| Advantage Business Property Consulting Ltd | Professional & scientific | 2014 |
| Advantage Media Network Ltd | Information & communication | 2008 |
| Advantage Publishing (UK) Ltd | Information & communication | 2006 |
| Adventure Centre Horsham Ltd | Administrative & support | 2025 |
| Adventurers Guild Ltd | Wholesale & retail | 2023 |
| Adventurers Properties Ltd | Real estate | 2025 |
| Advise US Ltd | Education | 2016 |
| AEC Holdings Ltd | Professional & scientific | 2018 |
| AEC Residential Limited | Real estate | 2024 |
| Aegean International Pool Supplies Limited | Extraterritorial | 1987 |
| Aegean Spas (Projects) Ltd | Construction | 2022 |
| Aegean Spas Limited | Wholesale & retail | 1987 |
| Aegis Roofing Products Ltd | Wholesale & retail | 2023 |
| Aegyssus Limited | Manufacturing | 2021 |
| Aeko Ltd | Agriculture & fishing | 2021 |
| Aerco Limited | Wholesale & retail | 1956 |
| Aerial Training Services Limited | Manufacturing | 2022 |
| Aero Healthcare Ltd | Wholesale & retail | 2008 |
| Aerospace Chemical Supplies Limited | Wholesale & retail | 2012 |
| Affiniti Group Ltd | Information & communication | 2022 |
| Affinity Exchange Limited | Financial services | 2021 |
| Affken Associates Ltd | Administrative & support | 2018 |
| Afshaology Ltd | Other services | 2025 |
| AG Aviation Elite Ltd | Manufacturing | 2025 |
| AG Nexus Limited | Real estate | 2024 |
| Against the Grain London Ltd | Construction | 2020 |
| Agarwal Group Ltd | Information & communication | 2024 |
| Agile Rose Marketing Limited | Professional & scientific | 2013 |
| Agim Lucky Healthcare Limited | Health & social care | 2019 |
| AGK Carpentry & Construction Ltd | Construction | 2020 |
| Agribiomed UK Ltd | Health & social care | 2018 |
| Agricon Engineering Limited | Professional & scientific | 2012 |
| Agritrade-Ak Limited | Wholesale & retail | 2015 |
| AH Ventures Ltd | Professional & scientific | 2026 |
| Ahaan Corporation Ltd | Wholesale & retail | 2012 |
| Ahandf Ltd | Other services | 2015 |
| AHS Systems Ltd | Manufacturing | 2017 |
| AI Services (UK) Limited | Real estate | 2008 |
| AI4GP Ltd | Information & communication | 2024 |
| AIC Projects Ltd | Professional & scientific | 2025 |
| Aiden Care Limited | Health & social care | 2016 |
| Aids Strategy Advocacy and Policy Ltd | Professional & scientific | 2011 |
| Aikman Consultancy Limited | Administrative & support | 2020 |
| AIM Engineering Limited | Construction | 2022 |
| Ainsmere Properties Limited | Real estate | 2011 |
| AIP Exhibitions Limited | Administrative & support | 2015 |
| Air & Land Repatriation Services Limited | Extraterritorial | 2022 |
| Air Cargo Trader Limited | Transport & logistics | 1986 |
| Air Conditioning Direct Limited | Construction | 1995 |
| Air England Limited | Professional & scientific | 1994 |
| Air Land & Sea Repatriation Services Ltd | Health & social care | 2022 |
| Air Passenger Solicitors Limited | Professional & scientific | 2019 |
| Air Quality Measurements Limited | Professional & scientific | 2002 |
| Air Revolution Technologies International Ltd | Professional & scientific | 2020 |
| Airport Chauffeurs 24 Ltd | Transport & logistics | 2024 |
| Aixial Group UK Limited | Professional & scientific | 2001 |
| Aixial UK Limited | Professional & scientific | 1999 |
| AJ & Associates Ltd | Education | 2017 |
| AJ Audio Ltd | Information & communication | 2022 |
| AJ Mcewan Horsham Ltd | Manufacturing | 2016 |
| AJ Mcewan Ltd | Manufacturing | 2025 |
| AJ Valet & Detailing Ltd. | Administrative & support | 2024 |
| Ajese Limited | Real estate | 2018 |
| AJW Hospitality Ltd | Hospitality | 2024 |
| AJW Technique Europe Limited | Transport & logistics | 2012 |
| Ajwte Holdings Limited | Manufacturing | 2020 |
| AK Footcare Ltd | Health & social care | 2025 |
| AK Property Developments Limited | Construction | 2013 |
| Akkurt Barber Ltd | Other services | 2022 |
| Akll Ltd | Professional & scientific | 2023 |
| AKP Directors Limited | Extraterritorial | 1998 |
| AKP Marketing Limited | Administrative & support | 2003 |
| AKP Secretaries Limited | Extraterritorial | 1998 |
| AL Campbell Author Limited | Arts & recreation | 2021 |
| AL Hamrah Ltd | Hospitality | 2025 |
| Alan the GAS MAN Limited | Construction | 2026 |
| Alanah Limited | Professional & scientific | 2010 |
| Alastair Burns & Co Ltd. | Professional & scientific | 1998 |
| Alchemy Mill LLP | | 2013 |
| Alembic TV Limited | Information & communication | 2009 |
| Aletheia Media Limited | Information & communication | 2022 |
| Alex Gale Digital Ltd | Information & communication | 2023 |
| Alex Harvey Estate Agents Limited | Real estate | 2018 |
| Alexander Integrated Systems Limited | Administrative & support | 2022 |
| Alexander Montgomery Coordination Ltd | Hospitality | 2025 |
| Alexander Winston Ltd | Real estate | 2025 |
| Alexandrakay Limited | Other services | 2014 |
| ALF Shrubb Memorial Race CIC | Arts & recreation | 2024 |
| Alfred Lancaster Gunmakers Limited | Manufacturing | 2006 |
| Alfson Consultancy Limited | Professional & scientific | 2008 |
| ALI Rigging Ltd | Construction | 2026 |
| Alinka Limited | Wholesale & retail | 2018 |
| Alison Mary Frances Hill Limited | Extraterritorial | 2023 |
| Alison Wondermaids Ltd | Administrative & support | 2023 |
| Aliya Drake Therapy Ltd | Health & social care | 2024 |
| Ali’S Mechanical Repair Centre Limited | Wholesale & retail | 2026 |
| ALL Finance Ltd | Financial services | 2026 |