| AK Richmond Car Valeting Co Ltd | Health & social care | 2021 |
| Akavi UK Limited | Information & communication | 2020 |
| Akhtar Group Ltd | Real estate | 2025 |
| Akle Healthcare Support Ltd | Health & social care | 2023 |
| AKS Home Services Limited | Construction | 2026 |
| AL Kanz Ltd | Hospitality | 2019 |
| AL Sims Ltd | Construction | 2023 |
| Al-Shifa Healthcare Ltd | Health & social care | 2022 |
| Alaam Motortrade Ltd | Wholesale & retail | 2025 |
| Alabaster Oryx Ltd | Professional & scientific | 2021 |
| Alam Motortrade Ltd | Wholesale & retail | 2023 |
| Alan Bonny Thomas Holdings Limited | Wholesale & retail | 2025 |
| Alan Mann Racing Limited | Wholesale & retail | 2002 |
| Alan Overton Builders Limited | Construction | 2021 |
| Alan Tiling Services Ltd | Other services | 2024 |
| Alanson Limited | Wholesale & retail | 2007 |
| Albatross Systems Limited | Information & communication | 2025 |
| Albeir Resorts Limited | Hospitality | 2024 |
| Albeir Resorts Midco Limited | Professional & scientific | 2025 |
| Albexco Ltd | Professional & scientific | 2023 |
| Albury Road Ltd | Construction | 2024 |
| Alby Limited | Health & social care | 2016 |
| Alchemy Photography Limited | Professional & scientific | 2013 |
| Alchemy Research & Consultancy Ltd | Professional & scientific | 2005 |
| Alchemy Testing Solutions Limited | Information & communication | 2022 |
| Alconomy Services Southern Limited | | 2011 |
| Alconomy Southern Limited | | 2011 |
| Alcura UK Limited | Wholesale & retail | 1994 |
| Aldahhan Properties Limited | Real estate | 2020 |
| Alderwood Consultancy Limited | Professional & scientific | 2009 |
| Aldgate Ltd | Administrative & support | 2015 |
| Aldwych Estates Limited | Real estate | 1971 |
| Alecris Consulting Limited | Administrative & support | 2018 |
| Alent Finance Limited | Professional & scientific | 2012 |
| Alent Holdings Brazil Limited | Professional & scientific | 2003 |
| Alent Investments Limited | Professional & scientific | 2012 |
| Alent Limited | Professional & scientific | 2012 |
| Alent New Finance (UK) Limited | Professional & scientific | 2012 |
| Alent New Mexico Holdings Limited | Professional & scientific | 2012 |
| Alex Barber Shop (Woking) Limited | Other services | 2025 |
| Alex Crockford Limited | Health & social care | 2016 |
| Alex Michael Company Ltd | Wholesale & retail | 2013 |
| Alex Props Limited | Other services | 2012 |
| Alexander David Motor Company Limited | Wholesale & retail | 1999 |
| Alexander James Mortgage Services Ltd | Financial services | 2009 |
| Alexander's Horticultural Services Ltd | Other services | 2018 |
| Alexandra Gibbs Properties Limited | Households | 2022 |
| Alexandru Eduard Ltd | Construction | 2025 |
| Alfix Construction Ltd | Construction | 2020 |
| Alicia Kate Ltd | Professional & scientific | 2024 |
| Alielectronics Limited | Wholesale & retail | 2021 |
| Alipha Limited | Education | 2014 |
| Alizay Beauty Ltd | Wholesale & retail | 2021 |
| ALK Consultancy Limited | Professional & scientific | 2025 |
| Alkebulan Capital Limited | Professional & scientific | 2021 |
| Alkhan & Co. Ltd | Information & communication | 2016 |
| Alkimi Ltd | Information & communication | 2009 |
| ALL -Sorts Property Maintenance and Carpentry Ltd | Construction | 2025 |
| ALL Angles Construction Limited | Construction | 2009 |
| ALL DE Andrade Ltd | Transport & logistics | 2024 |
| ALL Elements Landscaping Ltd | Administrative & support | 2023 |
| ALL Events Marquees Ltd | Administrative & support | 2006 |
| ALL Home Solutions Ltd | Other services | 2013 |
| ALL Kool Air (UK) Limited | Construction | 2013 |
| ALL Legal & More Limited | Professional & scientific | 2014 |
| ALL Patio Design Limited | Administrative & support | 2003 |
| ALL Saints Green Properties Limited | Real estate | 1965 |
| ALL Star Reserves Ltd | Professional & scientific | 2017 |
| Allbest Solutions Limited | Health & social care | 2018 |
| Alldred Construction Limited | Construction | 2018 |
| Allen Associates Tax Consulting LLP | | 2010 |
| Allen House Park Management Company Limited | Households | 1988 |
| Allergy Safe Foods Limited | Wholesale & retail | 2024 |
| Alliance Home Care (Learning Disabilities) Limited | Health & social care | 1996 |
| Alliance Home Care Limited | Health & social care | 1995 |
| Alliance UK CPH Limited | Transport & logistics | 2017 |
| Alliance Unichem IP Limited | Administrative & support | 2005 |
| Allied Care (Mental Health) Limited | Health & social care | 2001 |
| Allied Care (Supported Living) Limited | Health & social care | 2000 |
| Allied Care Head Office Limited | Financial services | 2019 |
| Allied Care Limited | Health & social care | 1995 |
| Allied Care Services Limited | Health & social care | 2013 |
| Allodium Limited | Extraterritorial | 2006 |
| Allpure Filters Limited | Wholesale & retail | 1976 |
| Allure Property London Ltd | Real estate | 2024 |
| Allwood Engineering LLP | | 2008 |
| Alman Limited | Wholesale & retail | 1991 |
| Almond Tree Pictures Limited | Information & communication | 2011 |
| Almus Pharmaceuticals Limited | Administrative & support | 2004 |
| Aloha Business Company Ltd | Wholesale & retail | 2025 |
| Alow Enterprise Limited | Professional & scientific | 2020 |
| Alpha Community Outreach Limited | Health & social care | 2011 |
| Alpha Hub Ltd | Wholesale & retail | 2025 |
| Alpha Launchpad Consulting Ltd | Information & communication | 2020 |
| Alpinewedge Limited | Real estate | 1982 |
| Alps Partnership Limited | Education | 2003 |
| Alspro Holdings Limited | Information & communication | 2004 |
| Alston Gardens Residents Limited | Households | 1994 |
| Altaf Contracting Limited | Wholesale & retail | 2024 |
| Alto Associates Limited | Information & communication | 2010 |