| AIM Scaffolding Limited | Construction | 2006 |
| AIM Trust Construction Ltd | Construction | 2016 |
| Aimer Media Limited | Information & communication | 2009 |
| AIN Consulting Services Limited | Information & communication | 2013 |
| Aintree Road 1979 Limited | Extraterritorial | 2015 |
| Air Atlanta Aviaservices Limited | Other services | 1998 |
| Air Atlanta UK Limited | Administrative & support | 1996 |
| Air Menzies International Limited | Other services | 1994 |
| Air Navigation Solutions Limited | Transport & logistics | 2014 |
| Air Safety Support International Limited | Public administration | 2000 |
| Airam SKM Limited | Health & social care | 2024 |
| Airbase UK Interiors Ltd | Manufacturing | 2019 |
| Aircraft Leasing and Management Limited | Transport & logistics | 1987 |
| Aircraft Simulation Services Limited | Manufacturing | 1997 |
| Aircraft Transport Worldwide UK Ltd | Transport & logistics | 2024 |
| Airooms Ltd | Construction | 2018 |
| Airport Cars Crawley Limited | Transport & logistics | 2023 |
| Airport Parking & Hotels (Birmingham) Limited | Professional & scientific | 2002 |
| Airport Parking & Hotels (Manchester) Limited | Professional & scientific | 1984 |
| Airport Parking (Gatwick) Limited | Professional & scientific | 1995 |
| Airport Parking and Hotels Limited | Administrative & support | 1981 |
| Airport World Ltd | Information & communication | 2025 |
| Airsoft Parts Ltd | Wholesale & retail | 2025 |
| Airtech Humidity Controls Limited | Construction | 1995 |
| Aizh Ltd | Education | 2021 |
| AJ Body Works Centre Limited | Wholesale & retail | 2013 |
| AJ Business Consultants Limited | Administrative & support | 2022 |
| AJ Digital Ltd | Information & communication | 2022 |
| AJ Nodes Ltd | Wholesale & retail | 2023 |
| Ajbuckley Consultancy Ltd | Professional & scientific | 2023 |
| AJI Properties Ltd | Real estate | 2025 |
| AJL Security Ltd | Administrative & support | 2023 |
| AJP Networking Limited | Wholesale & retail | 2011 |
| AK Domestics Limited | Administrative & support | 2023 |
| AK Gym Limited | Arts & recreation | 2020 |
| AK Home Improvements West Sussex Ltd | Construction | 2025 |
| AK Janitors Limited | Administrative & support | 2022 |
| AK247 Vending Ltd | Wholesale & retail | 2025 |
| Akal Consultancy Limited | Wholesale & retail | 2016 |
| Akar Auto Motors Limited | Wholesale & retail | 2023 |
| Akar Consultants and Accountants Limited | Professional & scientific | 2016 |
| Akar Trading Company Limited | Wholesale & retail | 2013 |
| Akarsini Property Group Ltd | Real estate | 2026 |
| Akash Accounting Services Ltd | Professional & scientific | 2013 |
| Akash Thakrar Ltd | Professional & scientific | 2024 |
| Akatal Ltd | Professional & scientific | 2021 |
| AKG Project Management Ltd | Professional & scientific | 2019 |
| Akiffi London Ltd | Wholesale & retail | 2026 |
| Aksa Sales Ltd | Wholesale & retail | 2022 |
| AKSA18 Ltd | Hospitality | 2020 |
| Aksanio UK Limited | Information & communication | 2025 |
| Akson Ltd | Construction | 2010 |
| Akta Properties Limited | Real estate | 2018 |
| Akubhi Properties Ltd | Real estate | 2020 |
| AL Canpainha Ltd | Hospitality | 2025 |
| AL Gambling Consulting Ltd | Arts & recreation | 2020 |
| AL Jannat International Logistics Ltd | Wholesale & retail | 2026 |
| AL Makkah Travel Limited | Administrative & support | 2022 |
| AL Noor Hajj Limited | Administrative & support | 2003 |
| AL QS & Commercial Services Ltd | Professional & scientific | 2015 |
| AL Raheem Ecommerce Ltd | Wholesale & retail | 2025 |
| AL Sadaat Limited | Transport & logistics | 2014 |
| Al&Xi Ltd | Transport & logistics | 2018 |
| Alagie Jadama Electrical Limited | Construction | 2023 |
| Alampati Limited | Information & communication | 2009 |
| Alastair Levy Advisory Ltd | Professional & scientific | 2024 |
| Albemarle Wholesale Ltd. | | 2008 |
| Albert RAY Developments Ltd | Construction | 2024 |
| Alchemy 3 D C Limited | Arts & recreation | 2002 |
| Alchemy Care (Greensleeves) Limited | Real estate | 2020 |
| Alchemy Care Holdings Limited | Health & social care | 2020 |
| Alchemy Care Property Limited | Real estate | 2020 |
| Alchemy-Evolved Ltd | Information & communication | 2021 |
| ALD Electrical Ltd | Construction | 2025 |
| Alders View Holdings Ltd | Construction | 2026 |
| Alee Tax & Accounts Ltd | Professional & scientific | 2025 |
| Alever Properties Limited | Extraterritorial | 2013 |
| Alexa Holding Ltd | Professional & scientific | 2026 |
| Alexandar Ltd | Wholesale & retail | 2023 |
| Alexandra & Daria Ltd | Health & social care | 2019 |
| Alexian Brothers of the Province of the Sacred Heart (the) | Health & social care | 1963 |
| Alfatahtraders Ltd | Wholesale & retail | 2025 |
| Alfresco Conservatories Limited | Administrative & support | 2003 |
| Alfresco Conservatories SE Limited | Administrative & support | 2025 |
| Algorita Ltd | Information & communication | 2019 |
| Algorta Solutions Limited | Administrative & support | 2016 |
| Algosys Consulting Limited | Information & communication | 2025 |
| Alhekmah Management Consultancy Limited | Administrative & support | 2021 |
| ALI Elite Autos Limited | Transport & logistics | 2024 |
| Alibi Services Ltd | Construction | 2025 |
| Aligned Surveying Ltd | Professional & scientific | 2019 |
| Alina Rahim Limited | Wholesale & retail | 2023 |
| Alinet Services Limited | Wholesale & retail | 2021 |
| Alisanmar Limited | Transport & logistics | 2022 |
| Alisha and Charlotte Event Displays Limited | Professional & scientific | 2021 |
| Alium Developments Ltd | Construction | 2023 |
| Alium Global Holdings Limited | Financial services | 2023 |
| Alium Global Ltd | Construction | 2014 |
| Alkira Services Ltd | Administrative & support | 2008 |
| ALL 4 Bar Ltd | Wholesale & retail | 2024 |