| Alkas Properties Ltd | Real estate | 2024 |
| ALL Abroad Ltd | Information & communication | 2025 |
| ALL Aspects Cooling and Heating Limited | Construction | 2025 |
| ALL Level Lifts Limited | Manufacturing | 2023 |
| ALL Vehicle Services Limited | Wholesale & retail | 2017 |
| Allegro.Law Limited | Professional & scientific | 2026 |
| Allentay Limited | Professional & scientific | 2018 |
| Allenvale Limited | Real estate | 2016 |
| Alley Farm Livery Services Limited | Arts & recreation | 2017 |
| Allstones Limited | Construction | 2025 |
| Allstructure Renovations Ltd | Construction | 2025 |
| Almac Carpentry and Joinery Ltd. | Construction | 2005 |
| Almsford Investment Ltd | Other services | 2021 |
| Alnotics Limited | Manufacturing | 2017 |
| Alpha Aviation Engineering (Finmere) Ltd | Manufacturing | 2021 |
| Alpha Support Services Limited | Extraterritorial | 2023 |
| Alpha Tanker Services Limited | Water & waste | 2009 |
| Alpine Forestry Ltd | Agriculture & fishing | 2020 |
| Alpro (UK) Limited | Manufacturing | 1999 |
| ALS First AID Training Limited | Education | 2017 |
| Alscott Limited | Construction | 2020 |
| Alternative Strategies (U.K.) Limited | Professional & scientific | 2003 |
| Altin Top Transport Ltd | Transport & logistics | 2020 |
| Altitude Customs Limited | Wholesale & retail | 2025 |
| Altro Prime Limited | Construction | 2019 |
| Altum Vista Estates Ltd | Real estate | 2025 |
| Alumasc Building Products Limited | Manufacturing | 1994 |
| Alumasc Construction Products Limited | Extraterritorial | 1947 |
| Alumasc D Developments Limited | Extraterritorial | 1992 |
| Alumasc DD Limited | Extraterritorial | 1919 |
| Alumasc Exterior Building Products Limited | Extraterritorial | 1907 |
| Alumasc Holdings Limited | Extraterritorial | 1917 |
| Alumasc Interior Building Products Limited | Extraterritorial | 1999 |
| Alumasc Limited | Manufacturing | 1945 |
| Alumasc Precision Limited | Extraterritorial | 1999 |
| Alumasc-Grundy Limited | Extraterritorial | 1929 |
| Aluminium Roofline Products Limited | Manufacturing | 1999 |
| Alva Enterprises Limited | Wholesale & retail | 2014 |
| Alyt Homes Ltd | Construction | 2026 |
| AM Commercial Consultancy Limited | Professional & scientific | 2023 |
| AM Electrics (Renewables) Limited | Manufacturing | 2014 |
| AM Network Solutions Ltd | Information & communication | 2015 |
| Amao Products Limited | Extraterritorial | 2016 |
| Amazing Support Ltd | Health & social care | 2022 |
| AMB Hygiene Limited | Manufacturing | 1985 |
| Amber Enterprises (UK) Limited | Professional & scientific | 1998 |
| Amber Taxis Kettering Ltd | Transport & logistics | 2023 |
| Ambleside Leisure Limited | Hospitality | 1992 |
| AMC Print Solutions Ltd | Administrative & support | 2019 |
| AMD Truck Driver Ltd | Transport & logistics | 2018 |
| Amec Consultancy Limited | Professional & scientific | 2019 |
| Amend Home Appliance Care Ltd | Other services | 2021 |
| American Candy Market Ltd | Wholesale & retail | 2025 |
| AMG Consulting and Development Ltd | Construction | 2025 |
| AMG Print Solutions Limited | Manufacturing | 2025 |
| AMI Accounting Limited | Professional & scientific | 2013 |
| Amino+ Ltd | Hospitality | 2024 |
| Ammandg Limited | Wholesale & retail | 2012 |
| Amore Studios Ltd | Other services | 2024 |
| Amore Tanning Ltd | Other services | 2020 |
| Amos Business Computers Limited | Information & communication | 2007 |
| Ampfa Ltd | Health & social care | 2019 |
| Ampi Access Ltd | Manufacturing | 2025 |
| Ampm Apartments LLP | | 2016 |
| Ampolo Limited | Administrative & support | 2000 |
| Amps Electrical Solutions Ltd | Manufacturing | 2023 |
| Ampsair Leasing Limited | Administrative & support | 2021 |
| AMR Logan Press Ltd | Professional & scientific | 2025 |
| AMR Property Solutions (Northants) LLP | | 2018 |
| Amsyku Limited | Professional & scientific | 2021 |
| AMT Logistics Ltd | Transport & logistics | 2019 |
| Amtell Ltd | Other services | 2020 |
| AMY Cattle Ltd | Health & social care | 2026 |
| AMY Lianne Ltd | Wholesale & retail | 2021 |
| AMY Thalathoty Ltd | Health & social care | 2024 |
| AMY Web Ltd | Wholesale & retail | 2012 |
| AN Teallach Consultancy Limited | Professional & scientific | 2016 |
| Anadi Surgical Limited | Health & social care | 2015 |
| Anbr Ltd | Health & social care | 2026 |
| Anchora Ecosystem Limited | Information & communication | 2026 |
| Andare Ltd | Professional & scientific | 2023 |
| Andare Management Consulting Ltd | Professional & scientific | 2025 |
| Andare Travel Solutions Ltd | Wholesale & retail | 2025 |
| Anderstone SA Ltd | Real estate | 2018 |
| Andrew Foulds Limited | Agriculture & fishing | 1985 |
| Andrew Geotechnics PTY Ltd | Construction | 2017 |
| Andrew Pipework Services Limited | Construction | 2000 |
| Andrews Trading Services Ltd | Wholesale & retail | 2017 |
| Andstrat (NO. 417) LLP | | 2017 |
| Andstrat (NO.425) Limited | Other services | 2021 |
| Andy Brear Architectural Services Ltd | Professional & scientific | 2022 |
| Andy Dean Business Solutions Limited | Professional & scientific | 2014 |
| Andy Feakin Limited | Construction | 2003 |
| Andy Leeds Work Winning Limited | Professional & scientific | 2025 |
| Aneesaziz Ltd | Wholesale & retail | 2025 |
| Angell Wright Associates Ltd | Construction | 2022 |
| Anghel Developments Ltd | Real estate | 2026 |
| Anitha Rajkumar Ltd | Real estate | 2006 |
| Anja Ltd | Education | 2023 |
| Anna Alla Limited | Wholesale & retail | 2005 |